Design of a High Voltage Power Supply Providing a Force Field for a Fluid Experiment

NASA Astrophysics Data System (ADS)

Herty, Frank

2005-05-01

As part of the GeoFlow fluid experiment an ac high voltage power supply (HVPS) is used to establish high electrical fields on fluids based on silicon oil. The non- conductive fluid is encapsulated between two spherical electrodes. This experiment cell assembly acts essentially as a capacitive load.The GeoFlow HVPS is an integrated ac high voltage source capable to provide up to 10kVRMS on capacitive loads up to 100pF.This paper presents major design challenges and solutions regarding the high voltage transformer and its driver electronics. Particular high voltage problems like corona effects and dielectric losses are discussed and countermeasures are presented.

Model predictive direct power control for active power decoupled single-phase quasi- Z -source inverter

DOE PAGES

Liu, Yushan; Ge, Baoming; Abu-Rub, Haitham; ...

2016-06-14

In this study, the active power filter (APF) that consists of a half-bridge leg and an ac capacitor is integrated in the single-phase quasi-Z-source inverter (qZSI) in this paper to avoid the second harmonic power flowing into the dc side. The capacitor of APF buffers the second harmonic power of the load, and the ac capacitor allows highly pulsating ac voltage, so that the capacitances of both dc and ac sides can be small. A model predictive direct power control (DPC) is further proposed to achieve the purpose of this newtopology through predicting the capacitor voltage of APF at eachmore » sampling period and ensuring the APF power to track the second harmonic power of single-phase qZSI. Simulation and experimental results verify the model predictive DPC for the APF-integrated single-phase qZSI.« less

Model predictive direct power control for active power decoupled single-phase quasi- Z -source inverter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yushan; Ge, Baoming; Abu-Rub, Haitham

In this study, the active power filter (APF) that consists of a half-bridge leg and an ac capacitor is integrated in the single-phase quasi-Z-source inverter (qZSI) in this paper to avoid the second harmonic power flowing into the dc side. The capacitor of APF buffers the second harmonic power of the load, and the ac capacitor allows highly pulsating ac voltage, so that the capacitances of both dc and ac sides can be small. A model predictive direct power control (DPC) is further proposed to achieve the purpose of this newtopology through predicting the capacitor voltage of APF at eachmore » sampling period and ensuring the APF power to track the second harmonic power of single-phase qZSI. Simulation and experimental results verify the model predictive DPC for the APF-integrated single-phase qZSI.« less

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

1997-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2002-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2001-04-03

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with separate DC sources

DOEpatents

Peng, F.Z.; Lai, J.S.

1997-06-24

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations. 15 figs.

Unity power factor converter

NASA Technical Reports Server (NTRS)

Wester, Gene W. (Inventor)

1980-01-01

A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i.sub.ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

Method for measuring the alternating current half-wave voltage of a Mach-Zehnder modulator based on opto-electronic oscillation.

PubMed

Hong, Jun; Chen, Dongchu; Peng, Zhiqiang; Li, Zulin; Liu, Haibo; Guo, Jian

2018-05-01

A new method for measuring the alternating current (AC) half-wave voltage of a Mach-Zehnder modulator is proposed and verified by experiment in this paper. Based on the opto-electronic self-oscillation technology, the physical relationship between the saturation output power of the oscillating signal and the AC half-wave voltage is revealed, and the value of the AC half-wave voltage is solved by measuring the saturation output power of the oscillating signal. The experimental results show that the measured data of this new method involved are in agreement with a traditional method, and not only an external microwave signal source but also the calibration for different frequency measurements is not needed in our new method. The measuring process is simplified with this new method on the premise of ensuring the accuracy of measurement, and it owns good practical value.

Needle-array to Plate DBD Plasma Using Sine AC and Nanosecond Pulse Excitations for Purpose of Improving Indoor Air Quality

PubMed Central

Zhang, Li; Yang, Dezheng; Wang, Wenchun; Wang, Sen; Yuan, Hao; Zhao, Zilu; Sang, Chaofeng; Jia, Li

2016-01-01

In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed. PMID:27125663

Rectilinear accelerometer possesses self- calibration feature

NASA Technical Reports Server (NTRS)

Henderson, R. B.

1966-01-01

Rectilinear accelerometer operates from an ac source with a phase-sensitive ac voltage output proportional to the applied accelerations. The unit includes an independent circuit for self-test which provides a sensor output simulating an acceleration applied to the sensitive axis of the accelerometer.

Mitigating voltage lead errors of an AC Josephson voltage standard by impedance matching

NASA Astrophysics Data System (ADS)

Zhao, Dongsheng; van den Brom, Helko E.; Houtzager, Ernest

2017-09-01

A pulse-driven AC Josephson voltage standard (ACJVS) generates calculable AC voltage signals at low temperatures, whereas measurements are performed with a device under test (DUT) at room temperature. The voltage leads cause the output voltage to show deviations that scale with the frequency squared. Error correction mechanisms investigated so far allow the ACJVS to be operational for frequencies up to 100 kHz. In this paper, calculations are presented to deal with these errors in terms of reflected waves. Impedance matching at the source side of the system, which is loaded with a high-impedance DUT, is proposed as an accurate method to mitigate these errors for frequencies up to 1 MHz. Simulations show that the influence of non-ideal component characteristics, such as the tolerance of the matching resistor, the capacitance of the load input impedance, losses in the voltage leads, non-homogeneity in the voltage leads, a non-ideal on-chip connection and inductors between the Josephson junction array and the voltage leads, can be corrected for using the proposed procedures. The results show that an expanded uncertainty of 12 parts in 106 (k  =  2) at 1 MHz and 0.5 part in 106 (k  =  2) at 100 kHz is within reach.

Border Collision of Three-Phase Voltage-Source Inverter System with Interacting Loads

NASA Astrophysics Data System (ADS)

Li, Zhen; Liu, Bin; Li, Yining; Wong, Siu-Chung; Liu, Xiangdong; Huang, Yuehui

As a commercial interface, three-phase voltage-source inverters (VSI) are commonly equipped for energy conversion to export DC power from most distributed generation (DG) to the AC utility. Not only do voltage-source converters take charge of converting the power to the loads but support the grid voltage at the point of common connection (PCC) as well, which is dependent on the condition of the grid-connected loads. This paper explores the border collision and its interacting mechanism among the VSI, resistive interacting loads and grids, which manifests as the alternating emergence of the inverting and rectifying operations, where the normal operation is terminated and a new one is assumed. Their mutual effect on the power quality under investigation will cause the circuital stability issue and further deteriorate the voltage regulation capability of VSI by dramatically raising the grid voltage harmonics. It is found in a design-oriented view that the border collision operation will be induced within the unsuitable parameter space with respect to transmission lines of AC grid, resistive loads and internal resistance of VSI. The physical phenomenon is also identified by the theoretical analysis. With numerical simulations for various circuit conditions, the corresponding bifurcation boundaries are collected, where the stability of the system is lost via border collision.

Variable-frequency inverter controls torque, speed, and braking in ac induction motors

NASA Technical Reports Server (NTRS)

Nola, F. J.

1974-01-01

Dc to ac inverter provides optimum frequency and voltage to ac induction motor, in response to different motor-load and speed requirements. Inverter varies slip frequency of motor in proportion to required torque. Inverter protects motor from high current surges, controls negative slip to apply braking, and returns energy stored in momentum of load to dc power source.

A new AC driving circuit for a top emission AMOLED

NASA Astrophysics Data System (ADS)

Yongwen, Zhang; Wenbin, Chen; Haohan, Liu

2013-05-01

A new voltage programmed pixel circuit with top emission design for active-matrix organic light-emitting diode (AMOLED) displays is presented and verified by HSPICE simulations. The proposed pixel circuit consists of five poly-Si TFTs, and can effectively compensate for the threshold voltage variation of the driving TFT. Meanwhile, the proposed pixel circuit offers an AC driving mode for the OLED by the two adjacent pulse voltage sources, which can suppress the degradation of the OLED. Moreover, a high contrast ratio can be achieved by the proposed pixel circuit since the OLED does not emit any light except for the emission period.

Variable frequency inverter for ac induction motors with torque, speed and braking control

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1975-01-01

A variable frequency inverter was designed for driving an ac induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a dc power source.

Centralized vs decentralized lunar power system study

NASA Astrophysics Data System (ADS)

Metcalf, Kenneth; Harty, Richard B.; Perronne, Gerald E.

1991-09-01

Three power-system options are considered with respect to utilization on a lunar base: the fully centralized option, the fully decentralized option, and a hybrid comprising features of the first two options. Power source, power conditioning, and power transmission are considered separately, and each architecture option is examined with ac and dc distribution, high and low voltage transmission, and buried and suspended cables. Assessments are made on the basis of mass, technological complexity, cost, reliability, and installation complexity, however, a preferred power-system architecture is not proposed. Preferred options include transmission based on ac, transmission voltages of 2000-7000 V with buried high-voltage lines and suspended low-voltage lines. Assessments of the total cost associated with the installations are required to determine the most suitable power system.

Research on Three-phase Four-wire Inverter

NASA Astrophysics Data System (ADS)

Xin, W. D.; Li, X. K.; Huang, G. Z.; Fan, X. C.; Gong, X. J.; Sun, L.; Wang, J.; Zhu, D. W.

2017-05-01

The concept of Voltage Source Converter (VSC) based hybrid AC and DC distribution system architecture is proposed, which can solve the traditional AC distribution power quality problems and respond to the request of DC distribution development. At first, a novel VSC system structure combining the four-leg based three-phase four-wire with LC filter is adopted, using the overall coordination control scheme of the AC current tracking compensation based grid-interfaced VSC. In the end, the 75 kW simulation experimental system is designed and tested to verify the performance of the proposed VSC under DC distribution, distributed DC sources conditions, as well as power quality management of AC distribution.

Voltage source ac-to-dc converters for high-power transmitters

NASA Technical Reports Server (NTRS)

Cormier, R.

1990-01-01

This work was done to optimize the design of the components used for the beam power supply, which is a component of the transmitters in the Deep Space Network (DSN). The major findings are: (1) the difference in regulation between a six-pulse and a twelve-pulse converter is at most 7 percent worse for the twelve-pulse converter; (2) the commutation overlap angle of a current source converter equals that of a voltage source converter with continuous line currents; (3) the sources of uncharacteristic harmonics are identified with SPICE simulation; (4) the use of an imperfect phase-shifting transformer for the twelve-pulse converter generates a harmonic at six times the line frequency; and (5) the assumptions usually made in analyzing converters can be relaxed with SPICE simulation. The results demonstrate the suitability of using SPICE simulation to obtain detailed performance predictions of ac-to-dc converters.

Solid state light source driver establishing buck or boost operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, Fred

A solid state light source driver circuit that operates in either a buck convertor or a boost convertor configuration is provided. The driver circuit includes a controller, a boost switch circuit and a buck switch circuit, each coupled to the controller, and a feedback circuit, coupled to the light source. The feedback circuit provides feedback to the controller, representing a DC output of the driver circuit. The controller controls the boost switch circuit and the buck switch circuit in response to the feedback signal, to regulate current to the light source. The controller places the driver circuit in its boostmore » converter configuration when the DC output is less than a rectified AC voltage coupled to the driver circuit at an input node. The controller places the driver circuit in its buck converter configuration when the DC output is greater than the rectified AC voltage at the input node.« less

Modulation and control of matrix converter for aerospace application

NASA Astrophysics Data System (ADS)

Kobravi, Keyhan

In the context of modern aircraft systems, a major challenge is power conversion to supply the aircraft's electrical instruments. These instruments are energized through a fixed-frequency internal power grid. In an aircraft, the available sources of energy are a set of variable-speed generators which provide variable-frequency ac voltages. Therefore, to energize the internal power grid of an aircraft, the variable-frequency ac voltages should be converted to a fixed-frequency ac voltage. As a result, an ac to ac power conversion is required within an aircraft's power system. This thesis develops a Matrix Converter to energize the aircraft's internal power grid. The Matrix Converter provides a direct ac to ac power conversion. A major challenge of designing Matrix Converters for aerospace applications is to minimize the volume and weight of the converter. These parameters are minimized by increasing the switching frequency of the converter. To design a Matrix Converter operating at a high switching frequency, this thesis (i) develops a scheme to integrate fast semiconductor switches within the current available Matrix Converter topologies, i.e., MOSFET-based Matrix Converter, and (ii) develops a new modulation strategy for the Matrix Converter. This Matrix Converter and the new modulation strategy enables the operation of the converter at a switching-frequency of 40kHz. To provide a reliable source of energy, this thesis also develops a new methodology for robust control of Matrix Converter. To verify the performance of the proposed MOSFET-based Matrix Converter, modulation strategy, and control design methodology, various simulation and experimental results are presented. The experimental results are obtained under operating condition present in an aircraft. The experimental results verify the proposed Matrix Converter provides a reliable power conversion in an aircraft under extreme operating conditions. The results prove the superiority of the proposed Matrix Converter technology for ac to ac power conversion regarding the existing technologies of Matrix Converters.

Converter topologies for common mode voltage reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, Fernando

An inverter includes a three-winding transformer, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, and an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adaptedmore » to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid. At least two of the DC-AC inverter, the cycloconverter, or the active filter are electrically coupled via a common reference electrical interconnect.« less

Laser guiding of Tesla coil high voltage discharges.

PubMed

Henriksson, Markus; Daigle, Jean-Francois; Théberge, Francis; Châteauneuf, Marc; Dubois, Jacques

2012-06-04

We have investigated the guiding and triggering of discharges from a Tesla coil type 280 kHz AC high voltage source using filaments created by a femtosecond Terawatt laser pulse. Without the laser the discharges were maximum 30 cm long. With the laser straight, guided discharges up to 110 cm length were detected. The discharge length was limited by the voltage amplitude of the Tesla coil.

Nonlinear control of voltage source converters in AC-DC power system.

PubMed

Dash, P K; Nayak, N

2014-07-01

This paper presents the design of a robust nonlinear controller for a parallel AC-DC power system using a Lyapunov function-based sliding mode control (LYPSMC) strategy. The inputs for the proposed control scheme are the DC voltage and reactive power errors at the converter station and the active and reactive power errors at the inverter station of the voltage-source converter-based high voltage direct current transmission (VSC-HVDC) link. The stability and robust tracking of the system parameters are ensured by applying the Lyapunov direct method. Also the gains of the sliding mode control (SMC) are made adaptive using the stability conditions of the Lyapunov function. The proposed control strategy offers invariant stability to a class of systems having modeling uncertainties due to parameter changes and exogenous inputs. Comprehensive computer simulations are carried out to verify the proposed control scheme under several system disturbances like changes in short-circuit ratio, converter parametric changes, and faults on the converter and inverter buses for single generating system connected to the power grid in a single machine infinite-bus AC-DC network and also for a 3-machine two-area power system. Furthermore, a second order super twisting sliding mode control scheme has been presented in this paper that provides a higher degree of nonlinearity than the LYPSMC and damps faster the converter and inverter voltage and power oscillations. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Improved transistorized AC motor controller for battery powered urban electric passenger vehicles

NASA Technical Reports Server (NTRS)

Peak, S. C.

1982-01-01

An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.

Experimental prototype of an electric elevator

NASA Astrophysics Data System (ADS)

Gaiceanu, M.; Epure, S.; Ciuta, S.

2016-08-01

The main objective is to achieve an elevator prototype powered by a three-phase voltage system via a bidirectional static power converter ac-ac with regenerating capability. In order to diminish the power size of the electric motor up to 1/3 of rated power, the elevator contains two carriages of the same weight, one serving as the payload, and the other as counterweight. Before proper operation of the static power converter, the capacitor must be charged at rated voltage via a precharge circuit. At the moment of stabilizing the DC voltage at nominal value, the AC-AC power converter can operates in the proper limits. The functions of the control structure are: the load control task, speed and torque controls. System includes transducers for current measuring, voltage sensors and encoder. As reserve power sources the hybrid battery-photovoltaic panels are used. The control voltage is modulated by implementing four types of pulse width modulations: sinusoidal, with reduced commutation, third order harmonic insertion, and the space vector modulation. Therefore, the prototype could operates with an increased efficiency, in spite of the existing ones. The experimental results confirm the well design of the chosen solution. The control solution assures bidirectional power flow control, precharge control, and load control and it is implemented on a digital signal processor. The elevator capacity is between 300-450 kg, and it is driven by using a 1.5 kW three-phase asynchronous machine.

An improved adaptive weighting function method for State Estimation in Power Systems with VSC-MTDC

NASA Astrophysics Data System (ADS)

Zhao, Kun; Yang, Xiaonan; Lang, Yansheng; Song, Xuri; Wang, Minkun; Luo, Yadi; Wu, Lingyun; Liu, Peng

2017-04-01

This paper presents an effective approach for state estimation in power systems that include multi-terminal voltage source converter based high voltage direct current (VSC-MTDC), called improved adaptive weighting function method. The proposed approach is simplified in which the VSC-MTDC system is solved followed by the AC system. Because the new state estimation method only changes the weight and keeps the matrix dimension unchanged. Accurate and fast convergence of AC/DC system can be realized by adaptive weight function method. This method also provides the technical support for the simulation analysis and accurate regulation of AC/DC system. Both the oretical analysis and numerical tests verify practicability, validity and convergence of new method.

New approaches to provide ride-through for critical loads in electric power distribution systems

NASA Astrophysics Data System (ADS)

Montero-Hernandez, Oscar C.

2001-07-01

The extensive use of electronic circuits has enabled modernization, automation, miniaturization, high quality, low cost, and other achievements regarding electric loads in the last decades. However, modern electronic circuits and systems are extremely sensitive to disturbances from the electric power supply. In fact, the rate at which these disturbances happen is considerable as has been documented in recent years. In response to the power quality concerns presented previously, this dissertation is proposing new approaches to provide ride-through for critical loads during voltage disturbances with emphasis on voltage sags. In this dissertation, a new approach based on an AC-DC-AC system is proposed to provide ride-through for critical loads connected in buildings and/or an industrial system. In this approach, a three-phase IGBT inverter with a built in Dc-link voltage regulator is suitably controlled along with static by-pass switches to provide continuous power to critical loads. During a disturbance, the input utility source is disconnected and the power from the inverter is connected to the load. The remaining voltage in the AC supply is converted to DC and compensated before being applied to the inverter and the load. After detecting normal utility conditions, power from the utility is restored to the critical load. In order to achieve an extended ride-through capability a second approach is introduced. In this case, the Dc-link voltage regulator is performed by a DC-DC Buck-Boost converter. This new approach has the capability to mitigate voltage variations below and above the nominal value. In the third approach presented in this dissertation, a three-phase AC to AC boost converter is investigated. This converter provides a boosting action for the utility input voltages, right before they are applied to the load. The proposed Pulse Width Modulation (PWM) control strategy ensures independent control of each phase and compensates for both single-phase or poly-phase voltage sags. Algorithms capable of detecting voltage disturbances such as voltage sags, voltage swells, flicker, frequency change, and harmonics in a fast and reliable way are investigated and developed in this dissertation as an essential part of the approaches previously described. Simulation and experimental work has been done to validate the feasibility of all approaches under the most common voltage disturbances such as single-phase voltage sags and three-phase voltage sags.

High-Performance AC Power Source by Applying Robust Stability Control Technology for Precision Material Machining

NASA Astrophysics Data System (ADS)

Chang, En-Chih

2018-02-01

This paper presents a high-performance AC power source by applying robust stability control technology for precision material machining (PMM). The proposed technology associates the benefits of finite-time convergent sliding function (FTCSF) and firefly optimization algorithm (FOA). The FTCSF maintains the robustness of conventional sliding mode, and simultaneously speeds up the convergence speed of the system state. Unfortunately, when a highly nonlinear loading is applied, the chatter will occur. The chatter results in high total harmonic distortion (THD) output voltage of AC power source, and even deteriorates the stability of PMM. The FOA is therefore used to remove the chatter, and the FTCSF still preserves finite system-state convergence time. By combining FTCSF with FOA, the AC power source of PMM can yield good steady-state and transient performance. Experimental results are performed in support of the proposed technology.

Transient AC voltage related phenomena for HVDC schemes connected to weak AC systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilotto, L.A.S.; Szechtman, M.; Hammad, A.E.

1992-07-01

In this paper a didactic explanation of voltage stability associated phenomena at HVDC terminals is presented. Conditions leading to ac voltage collapse problems are identified. A mechanism that excites control-induced voltage oscillations is shown. The voltage stability factor is used for obtaining the maximum power limits of ac/dc systems operating with different control strategies. Correlation to Pd {times} Id curves is given. Solutions for eliminating the risks of voltage collapse and for avoiding control-induced oscillations are discussed. The results are supported by detailed digital simulations of a weak ac/dc system using EMTP.

Dielectric Breakdown Characteristics of Oil-pressboard Insulation System against AC/DC Superposed Voltage

NASA Astrophysics Data System (ADS)

Ebisawa, Yoshihito; Yamada, Shin; Mori, Shigekazu; Ikeda, Masami

This paper describes breakdown characteristics of an oil-pressboard insulation system to a superposition voltage of AC and DC voltages. Although AC electric field is decided by the ratio of the relative permittivity of a pressboard and insulating oil, DC electric field is decided by ratio α of volume resistivities. From the measurement in this study, 13—78 and 1.8—5.7 are obtained as the volume resistivity ratios α at temperature of 30°C and 80°C, respectively. The breakdown voltages against AC, DC, and those superposition voltages are surveyed to insulation models. In normal temperature, the breakdown voltage to the superposition voltage of AC and DC is determined by AC electric field applied to the oil duct. Since the α becomes as low as 2-3 at temperature of 80°C, AC and DC voltages almost equally contribute to the electric field of the oil duct as a result. That is, it became clear that superposed DC voltage boosts the electric field across oil ducts at operating high temperature.

Alternating current corona discharge/atmospheric pressure chemical ionization for mass spectrometry.

PubMed

Habib, Ahsan; Usmanov, Dilshadbek; Ninomiya, Satoshi; Chen, Lee Chuin; Hiraoka, Kenzo

2013-12-30

Although alternating current (ac) corona discharge has been widely used in the fields of material science and technology, no reports have been published on its application to an atmospheric pressure chemical ionization (APCI) ion source. In this work, ac corona discharge for an APCI ion source has been examined for the first time. The ambient atmospheric pressure ac corona discharge (15 kHz, 2.6 kVptp ) was generated by using a stainless steel acupuncture needle. The generated ions were measured using an ion trap mass spectrometer. A comparative study on ac and direct current (dc) corona APCI ion sources was carried out using triacetone triperoxide and trinitrotoluene as test samples. The ac corona discharge gave ion signals as strong as dc corona discharge for both positive and negative ion modes. In addition, softer ionization was obtained with ac corona discharge than with dc corona discharge. The erosion of the needle tip induced by ac corona was less than that obtained with positive mode dc corona. A good 'yardstick' for assessing ac corona is that it can be used for both positive and negative ion modes without changing the polarity of the high-voltage power supply. Thus, ac corona can be an alternative to conventional dc corona for APCI ion sources. Copyright © 2013 John Wiley & Sons, Ltd.

Accelerating fissile material detection with a neutron source

DOEpatents

Rowland, Mark S.; Snyderman, Neal J.

2018-01-30

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly to count neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a Poisson neutron generator for in-beam interrogation of a possible fissile neutron source and a DC power supply that exhibits electrical ripple on the order of less than one part per million. Certain voltage multiplier circuits, such as Cockroft-Walton voltage multipliers, are used to enhance the effective of series resistor-inductor circuits components to reduce the ripple associated with traditional AC rectified, high voltage DC power supplies.

Experimental investigation of SDBD plasma actuator driven by AC high voltage with a superimposed positive pulse bias voltage

NASA Astrophysics Data System (ADS)

Qi, Xiao-Hua; Yan, Hui-Jie; Yang, Liang; Hua, Yue; Ren, Chun-Sheng

2017-08-01

In this work, a driven voltage consisting of AC high voltage with a superimposed positive pulse bias voltage ("AC+ Positive pulse bias" voltage) is adopted to study the performance of a surface dielectric barrier discharge plasma actuator under atmospheric conditions. To compare the performance of the actuator driven by single-AC voltage and "AC+ Positive pulse bias" voltage, the actuator-induced thrust force and power consumption are measured as a function of the applied AC voltage, and the measured results indicate that the thrust force can be promoted significantly after superimposing the positive pulse bias voltage. The physical mechanism behind the thrust force changes is analyzed by measuring the optical properties, electrical characteristics, and surface potential distribution. Experimental results indicate that the glow-like discharge in the AC voltage half-cycle, next to the cycle where a bias voltage pulse has been applied, is enhanced after applying the positive pulse bias voltage, and this perhaps is the main reason for the thrust force increase. Moreover, surface potential measurement results reveal that the spatial electric field formed by the surface charge accumulation after positive pulse discharge can significantly affect the applied external electric field, and this perhaps can be responsible for the experimental phenomenon that the decrease of thrust force is delayed by pulse bias voltage action after the filament discharge occurs in the glow-like discharge region. The schlieren images further verify that the actuator-induced airflow velocity increases with the positive pulse voltage.

Modelling a single phase voltage controlled rectifier using Laplace transforms

NASA Technical Reports Server (NTRS)

Kraft, L. Alan; Kankam, M. David

1992-01-01

The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.

AC to DC Bridgeless Boost Converter for Ultra Low Input Energy Harvesting

NASA Astrophysics Data System (ADS)

Dawam, A. H. A.; Muhamad, M.

2018-03-01

This paper presents design of circuit which converts low input AC voltage to a higher output DC voltage. A buck-boost topology and boost topology are combined to condition cycle of an AC input voltage. the unique integration of a combining circuit of buck-boost and boost circuit have been proposed in order to introduce a new direct ac-dc power converter topology without conventional diode bridge rectifier. The converter achieved to convert a milli-volt scale of input AC voltage into a volt scale of output DC voltages which is from 400mV to 3.3V.

A study of Schwarz converters for nuclear powered spacecraft

NASA Technical Reports Server (NTRS)

Stuart, Thomas A.; Schwarze, Gene E.

1987-01-01

High power space systems which use low dc voltage, high current sources such as thermoelectric generators, will most likely require high voltage conversion for transmission purposes. This study considers the use of the Schwarz resonant converter for use as the basic building block to accomplish this low-to-high voltage conversion for either a dc or an ac spacecraft bus. The Schwarz converter has the important assets of both inherent fault tolerance and resonant operation; parallel operation in modular form is possible. A regulated dc spacecraft bus requires only a single stage converter while a constant frequency ac bus requires a cascaded Schwarz converter configuration. If the power system requires constant output power from the dc generator, then a second converter is required to route unneeded power to a ballast load.

Dielectrophoresis device and method having non-uniform arrays for manipulating particles

DOEpatents

Cummings, Eric B [Livermore, CA; Fintschenko, Yolanda [Livermore, CA; Simmons, Blake [San Francisco, CA

2008-09-02

Microfluidic devices according to embodiments of the present invention include an inlet port, an outlet port, and a channel or chamber having a non-uniform array of insulating features on one or more surfaces. Electrodes are provided for generation of a spatially non-uniform electric field across the array. A voltage source, which may be an A.C. and/or a D.C. voltage source may be coupled to the electrodes for the generation of the electric field.

Dielectrophoresis device and method having nonuniform arrays for manipulating particles

DOEpatents

Cummings, Eric B.; Fintschenko, Yolanda; Simmons, Blake A.

2012-09-04

Microfluidic devices according to embodiments of the present invention include an inlet port, an outlet port, and a channel or chamber having a non-uniform array of insulating features on one or more surfaces. Electrodes are provided for generation of a spatially non-uniform electric field across the array. A voltage source, which may be an A.C. and/or a D.C. voltage source may be coupled to the electrodes for the generation of the electric field.

Simultaneous DC and three phase output using hybrid converter

NASA Astrophysics Data System (ADS)

Surenderanath, S.; Rathnavel, P.; Prakash, G.; Rayavel, P.

2018-04-01

This Paper introduces new hybrid converter topologies which can supply simultaneously three phase AC as well as DC from a single DC source. The new Hybrid Converter is derived from the single switch controlled Boost converter by replacing the controlled switch with voltage source inverter (VSI). This new hybrid converter has the advantages like reduced number of switches as compared with conventional design having separate converter for supplying three phase AC and DC loads, provide DC and three AC outputs with an increased reliability, resulting from the inherent shoot through protection in the inverter stage. The proposed converter, studied in this paper, is called Boost-Derived Hybrid Converter (BDHC) as it is obtained from the conventional boost topology. A DSPIC based feedback controller is designed to regulate the DC as well as AC outputs. The proposed Converter can supply DC and AC loads at 95 V and 35 V (line to ground) respectively from a 48 V DC source.

Performance Analysis of a Static Synchronous Compensator (STATCOM)

NASA Astrophysics Data System (ADS)

Kambey, M. M.; Ticoh, J. D.

2018-02-01

Reactive power and voltage are some of the problems in electric power supply and A Gate Turn Off (GTO) Static Synchronous Compensator (STATCOM) is one of the type of FACTS with shunt which can supply variable reactive power and regulate the voltage of the bus where it is connected. This study only discuss about the performance characteristic of the three phase six-pulse STATCOM by analysing the current wave flowing through DC Capacitor which depend on switching current and capacitor voltage wave. Simulation methods used in this research is started with a mathematical analysis of the ac current, dc voltage and current equations that pass STATCOM from a literature. The result shows the presence of the capacitor voltage ripple also alters the ac current waveform, even though the errors to be not very significant and the constraint of the symmetry circuit is valid if the source voltages have no zero sequence components and the impedances in all the three phases are identical. There for to improve STATCOM performance it is necessary to use multi-pulse 12, 24, 36, 48 or more, and/or with a multilevel converter.

Study on preferred crystal orientations of Mg-Zr-O composite protective layer in AC-PDP

NASA Astrophysics Data System (ADS)

Bingang, G.; Chunliang, L.; Zhongxiao, S.; Liu, L.; Yufeng, F.; Xing, X.; Duowang, F.

2006-11-01

In order to study the preferred crystal orientations of Mg-Zr-O composite protective layers in PDP, Mg-Zr-O composite protective layers were deposited by Electron-beam Evaporator using (MgO+ZrO{2}) powder mixture as evaporation source material. X-ray diffractometer (XRD) was used to determine preferred crystal orientations of Mg-Zr-O composite protective layers, surface morphologies of films were analyzed by FESEM and voltage characteristics were examined in a testing macroscopic discharge cell of AC-PDP. On the basis of experimental analysis, the influence of oxide addition and deposition conditions on preferred orientations of Mg-Zr-O composite protective layers were investigated. The results showed that the preferred orientations of Mg-Zr-O films were determined by lattice distortion of MgO crystal. The deposition conditions have great effects on the preferred orientations of Mg-Zr-O films. The preferred orientations affect voltage characteristics through affecting surface morphology of Mg-Zr-O films. A small amount of Zr solution in MgO can decrease firing voltage compared with using pure MgO film. Firing voltage is closely related with the [ ZrO{2}/(MgO+ZrO{2})] ratio of evaporation source materials.

Isolated and soft-switched power converter

DOEpatents

Peng, Fang Zheng; Adams, Donald Joe

2002-01-01

An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.

Electrical power inverter having a phase modulated, twin-inverter, high frequency link and an energy storage module

DOEpatents

Pitel, Ira J.

1987-02-03

The present invention provides an electrical power inverter method and apparatus, which includes a high frequency link, for converting DC power into AC power. Generally stated, the apparatus includes a first high frequency module which produces an AC voltage at a first output frequency, and a second high frequency inverter module which produces an AC voltage at a second output frequency that is substantially the same as the first output frequency. The second AC voltage is out of phase with the first AC voltage by a selected angular phase displacement. A mixer mixes the first and second output voltages to produce a high frequency carrier which has a selected base frequency impressed on the sidebands thereof. A rectifier rectifies the carrier, and a filter filters the rectified carrier. An output inverter inverts the filtered carrier to produce an AC line voltage at the selected base frequency. A phase modulator adjusts the relative angular phase displacement between the outputs of the first and second high frequency modules to control the base frequency and magnitude of the AC line voltage.

Electrical power inverter having a phase modulated, twin-inverter, high frequency link and an energy storage module

DOEpatents

Pitel, I.J.

1987-02-03

The present invention provides an electrical power inverter method and apparatus, which includes a high frequency link, for converting DC power into AC power. Generally stated, the apparatus includes a first high frequency module which produces an AC voltage at a first output frequency, and a second high frequency inverter module which produces an AC voltage at a second output frequency that is substantially the same as the first output frequency. The second AC voltage is out of phase with the first AC voltage by a selected angular phase displacement. A mixer mixes the first and second output voltages to produce a high frequency carrier which has a selected base frequency impressed on the sidebands thereof. A rectifier rectifies the carrier, and a filter filters the rectified carrier. An output inverter inverts the filtered carrier to produce an AC line voltage at the selected base frequency. A phase modulator adjusts the relative angular phase displacement between the outputs of the first and second high frequency modules to control the base frequency and magnitude of the AC line voltage. 19 figs.

Power Electronic Transformer based Three-Phase PWM AC Drives

NASA Astrophysics Data System (ADS)

Basu, Kaushik

A Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density. In this work a source based partially loss-less commutation of leakage energy has been proposed. This technique also results in partial soft-switching. A series of converters with novel PWM strategies have been proposed to minimize the frequency of leakage inductance commutation. These PETs achieve most of the important features of modern PWM ac drives including 1) Input power factor correction, 2) Common-mode voltage suppression at the load end, 3) High quality output voltage waveform (comparable to conventional space vector PWM modulated two level inverter) and 4) Minimization of output voltage loss, common-mode voltage switching and distortion of the load current waveform due to leakage inductance commutation. All of the proposed topologies along with the proposed control schemes have been analyzed and simulated in MATLABSimulink. A hardware prototype has been fabricated and tested. The simulation and experimental results verify the operation and advantages of the proposed topologies and their control.

High-frequency ac power distribution in Space Station

NASA Technical Reports Server (NTRS)

Tsai, Fu-Sheng; Lee, Fred C. Y.

1990-01-01

A utility-type 20-kHz ac power distribution system for the Space Station, employing resonant power-conversion techniques, is presented. The system converts raw dc voltage from photovoltaic cells or three-phase LF ac voltage from a solar dynamic generator into a regulated 20-kHz ac voltage for distribution among various loads. The results of EASY5 computer simulations of the local and global performance show that the system has fast response and good transient behavior. The ac bus voltage is effectively regulated using the phase-control scheme, which is demonstrated with both line and load variations. The feasibility of paralleling the driver-module outputs is illustrated with the driver modules synchronized and sharing a common feedback loop. An HF sinusoidal ac voltage is generated in the three-phase ac input case, when the driver modules are phased 120 deg away from one another and their outputs are connected in series.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aeloiza, Eddy C.; Burgos, Rolando P.

A step-down AC/AC converter for use in an electric distribution system includes at least one chopper circuit for each one of a plurality of phases of the AC power, each chopper circuit including a four-quadrant switch coupled in series between primary and secondary sides of the chopper circuit and a current-bidirectional two-quadrant switch coupled between the secondary side of the chopper circuit and a common node. Each current-bidirectional two-quadrant switch is oriented in the same direction, with respect to the secondary side of the corresponding chopper circuit and the common node. The converter further includes a control circuit configured tomore » pulse-width-modulate control inputs of the switches, to convert a first multiphase AC voltage at the primary sides of the chopper circuits to a second multiphase AC voltage at the secondary sides of the chopper circuits, the second multiphase AC voltage being lower in voltage than the first multiphase AC voltage.« less

Pulsed-DC DBD Plasma Actuators

NASA Astrophysics Data System (ADS)

Duong, Alan; Corke, Thomas; Thomas, Flint

2017-11-01

A power system for dielectric barrier discharge (DBD) plasma actuators that utilizes a pulsed-DC waveform is presented. The plasma actuator arrangement is identical to most typical AC-DBD designs with staggered electrodes that are separated by a dielectric insulator. A key difference is that the pulsed-DC actuator utilizes a DC voltage source to drive the actuator instead of an AC voltage input. The DC source is supplied to both electrodes. The exposed electrode remains constant in time while the encapsulated electrode is periodically grounded for short instances then is allowed to rise to the source DC level. Further investigation of the pulsed-DC plasma actuator was conducted. Time-resolved velocity measurements were done to characterize the induced velocity field generated by the pulsed-DC plasma actuator. A model of the pulsed-DC plasma actuator is developed in LTspice for further study. The work presented are intended in developing a model to be used in CFD flow control simulations. NASA SBIR NNX14CC12C.

System and component design and test of a 10 hp, 18,000 rpm AC dynamometer utilizing a high frequency AC voltage link, part 1

NASA Technical Reports Server (NTRS)

Lipo, Thomas A.; Alan, Irfan

1991-01-01

Hard and soft switching test results conducted with one of the samples of first generation MOS-controlled thyristor (MCTs) and similar test results with several different samples of second generation MCT's are reported. A simple chopper circuit is used to investigate the basic switching characteristics of MCT under hard switching and various types of resonant circuits are used to determine soft switching characteristics of MCT under both zero voltage and zero current switching. Next, operation principles of a pulse density modulated converter (PDMC) for three phase (3F) to 3F two-step power conversion via parallel resonant high frequency (HF) AC link are reviewed. The details for the selection of power switches and other power components required for the construction of the power circuit for the second generation 3F to 3F converter system are discussed. The problems encountered in the first generation system are considered. Design and performance of the first generation 3F to 3F power converter system and field oriented induction moter drive based upon a 3 kVA, 20 kHz parallel resonant HF AC link are described. Low harmonic current at the input and output, unity power factor operation of input, and bidirectional flow capability of the system are shown via both computer and experimental results. The work completed on the construction and testing of the second generation converter and field oriented induction motor drive based upon specifications for a 10 hp squirrel cage dynamometer and a 20 kHz parallel resonant HF AC link is discussed. The induction machine is designed to deliver 10 hp or 7.46 kW when operated as an AC-dynamo with power fed back to the source through the converter. Results presented reveal that the proposed power level requires additional energy storage elements to overcome difficulties with a peak link voltage variation problem that limits reaching to the desired power level. The power level test of the second generation converter after the addition of extra energy storage elements to the HF link are described. The importance of the source voltage level to achieve a better current regulation for the source side PDMC is also briefly discussed. The power levels achieved in the motoring mode of operation show that the proposed power levels achieved in the generating mode of operation can also be easily achieved provided that no mechanical speed limitation were present to drive the induction machine at the proposed power level.

Multilevel-Dc-Bus Inverter For Providing Sinusoidal And Pwm Electrical Machine Voltages

DOEpatents

Su, Gui-Jia [Knoxville, TN

2005-11-29

A circuit for controlling an ac machine comprises a full bridge network of commutation switches which are connected to supply current for a corresponding voltage phase to the stator windings, a plurality of diodes, each in parallel connection to a respective one of the commutation switches, a plurality of dc source connections providing a multi-level dc bus for the full bridge network of commutation switches to produce sinusoidal voltages or PWM signals, and a controller connected for control of said dc source connections and said full bridge network of commutation switches to output substantially sinusoidal voltages to the stator windings. With the invention, the number of semiconductor switches is reduced to m+3 for a multi-level dc bus having m levels. A method of machine control is also disclosed.

Numerical and Analytical Model of an Electrodynamic Dust Shield for Solar Panels on Mars

NASA Technical Reports Server (NTRS)

Calle, C. I.; Linell, B.; Chen, A.; Meyer, J.; Clements, S.; Mazumder, M. K.

2006-01-01

Masuda and collaborators at the University of Tokyo developed a method to confine and transport particles called the electric curtain in which a series of parallel electrodes connected to an AC source generates a traveling wave that acts as a contactless conveyor. The curtain electrodes can be excited by a single-phase or a multi-phase AC voltage. A multi-phase curtain produces a non-uniform traveling wave that provides controlled transport of those particles [1-6]. Multi-phase electric curtains from two to six phases have been developed and studied by several research groups [7-9]. We have developed an Electrodynamic Dust Shield prototype using threephase AC voltage electrodes to remove dust from surfaces. The purpose of the modeling work presented here is to research and to better understand the physics governing the electrodynamic shield, as well as to advance and to support the experimental dust shield research.

Modular inverter system

DOEpatents

Ma, Mingyao; Hu, Haibing; Kutkut, Nasser; Batarseh, Issa; Shen, John; , Bkayrat, Raed

2017-08-01

A system connected to an AC power grid having an AC phase signal includes an inverter module including a first inverter coupled to a DC voltage, actuated based on the AC phase signal. The first inverter provides a first voltage signal having predetermined harmonic components. A second inverter includes second switch elements coupled to the DC voltage and actuated by a second set of control signals phase delayed with respect to the first control signals. A transformer module has first and second primary windings coupled to the first and second inverters. The transformer module further includes a secondary winding coupled to first primary winding, the second primary winding, and the AC power grid. The secondary winding is configured to provide a secondary output voltage to the AC power grid by combining the first voltage signal and the second voltage signal such that the predetermined harmonic components are substantially cancelled.

Electrical Behavior of Copper Mine Tailings During EKR with Modified Electric Fields.

PubMed

Rojo, Adrian; Hansen, Henrik K; Monárdez, Omara; Jorquera, Carlos; Santis, Paulina; Inostroza, Paula

2017-03-01

Electro-kinetic remediation (EKR) with sinusoidal electric field obtained simultaneously with DC/AC voltage reduce the polarization of the EKR with DC voltage. The DC voltage value defines the presence of a periodic polarity reversal of the cell and the electrical charge for electro-kinetic transport. In this case, the AC frequency favors the breaking of polarization conditions resulting from the EKR with DC voltage. However, with high frequencies a negative effect occurs where the tailings behave as a filter circuit, discriminating frequencies of an electric signal. The goal of this work is to analyse the electrical behaviour of tailings in EKR experiments. The conditions selected were: DC/AC voltages: 10/15 and 20/25 V (peak values), and AC voltage frequencies 50-2000 Hz. When the AC frequency reaches 2000 Hz, the copper removal tends to zero, indicating that the tailing behaves as a high-pass filter in which the DC voltage was filtered out.

Grid-connected wind and photovoltaic system

NASA Astrophysics Data System (ADS)

Devabakthuni, Sindhuja

The objective of this thesis is to design a grid connected wind and photovoltaic system. A new model of converter control was designed which maintains the voltage of the bus to grid as constant when combined system of solar and wind is connected to AC bus. The model is designed to track maximum power at each point irrespective of changes in irradiance, temperature and wind speed which affects the power supplied to grid. Solar power from the sun is not constant as it is affected by changes in irradiances and temperature. Even the wind power is affected by wind speed. A MPPT controller was designed for both systems. A boost converter is designed which uses the pulses from MPPT controller to boost the output. Wind system consists of wind turbine block from the MATLAB with a pitch angle controller to maintain optimum pitch angle. The output from wind turbine is connected to a permanent magnet synchronous generator. The unregulated DC output from the photovoltaic system is directly given to boost converter. The AC output from the wind system is given to an uncontrolled rectifier to get a unregulated DC output. The unregulated DC output goes to the boost converter. A voltage source inverter was designed which converts the rectified DC output from the boost converter to AC power. The inverter is designed to maintain constant AC bus voltage irrespective of the disturbances in the power supply. Photovoltaic and wind systems are individually designed for 5KW each in MATLAB-Simulink environment. In this thesis, the models were subjected to changes in irradiance, temperature and wind speed and the results were interpreted. The model was successful in tracking maximum at every instant and the AC bus voltage was maintained constant throughout the simulation.

A battery simulator

NASA Technical Reports Server (NTRS)

Ferrell, S., Jr.; Lahr, N.

1970-01-01

Simulator verifies proper operation of a battery cell voltage-monitoring device. It also contains variable ac voltage to ascertain that a battery scanner will perform its function at all possible ac voltages.

Quench Detection and Protection for High Temperature Superconducting Transformers by Using the Active Power Method

NASA Astrophysics Data System (ADS)

Nanato, N.; Kobayashi, Y.

AC high temperature superconducting (HTS) coils have been developed for transformers, motors and so on. Quench detection and protection system are essential for safety operations of the AC HTS facilities. The balance voltage method is universally used for the quench detection and protection, however especially for AC operations, the method has risks in terms of high voltage sparks. Because the method needs a voltage tap soldered to a midpoint of the coil winding and the AC HTS facilities generally operate at high voltages and therefore high voltage sparks may occur at the midpoint with no insulation. We have proposed the active power method for the quench detection and protection. The method requires no voltage tap on the midpoint of the coil winding and therefore it has in-built effectiveness for the AC HTS facilities. In this paper, we show that the method can detect the quench in an HTS transformer and moreover our proposed quench protection circuits which consist of thyristors are simple and useful for the AC HTS facilities.

Determination of appropriate DC voltage for switched mode power supply (SMPS) loads

NASA Astrophysics Data System (ADS)

Setiawan, Eko Adhi; Setiawan, Aiman; Purnomo, Andri; Djamal, Muchlishah Hadi

2017-03-01

Nowadays, most of modern and efficient household electronic devices operated based on Switched Mode Power Supply (SMPS) technology which convert AC voltage from the grid to DC voltage. Based on theory and experiment, SMPS loads could be supplied by DC voltage. However, the DC voltage rating to energize electronic home appliances is not standardized yet. This paper proposed certain method to determine appropriate DC voltage, and investigated comparison of SMPS power consumption which is supplied from AC and DC voltage. To determine the appropriate DC voltage, lux value of several lamps which have same specification energized by using AC voltage and the results is using as reference. Then, the lamps were supplied by various DC voltage to obtain the trends of the lux value to the applied DC voltage. After that, by using the trends and the reference lux value, the appropriate DC voltage can be determined. Furthermore, the power consumption on home appliances such as mobile phone, laptop and personal computer by using AC voltage and the appropriate DC voltage were conducted. The results show that the total power consumption of AC system is higher than DC system. The total power (apparent power) consumed by the lamp, mobile phone and personal computer which operated in 220 VAC were 6.93 VA, 34.31 VA and 105.85 VA respectively. On the other hand, under 277 VDC the load consumption were 5.83 W, 19.11 W and 74.46 W respectively.

Input-current shaped ac to dc converters

NASA Technical Reports Server (NTRS)

1986-01-01

The problem of achieving near unity power factor while supplying power to a dc load from a single phase ac source of power is examined. Power processors for this application must perform three functions: input current shaping, energy storage, and output voltage regulation. The methods available for performing each of these three functions are reviewed. Input current shaping methods are either active or passive, with the active methods divided into buck-like and boost-like techniques. In addition to large reactances, energy storage methods include resonant filters, active filters, and active storage schemes. Fast voltage regulation can be achieved by post regulation or by supplementing the current shaping topology with an extra switch. Some indications of which methods are best suited for particular applications concludes the discussion.

Recent Advances in Alternating Current-Driven Organic Light-Emitting Devices.

PubMed

Pan, Yufeng; Xia, Yingdong; Zhang, Haijuan; Qiu, Jian; Zheng, Yiting; Chen, Yonghua; Huang, Wei

2017-11-01

Organic light-emitting devices (OLEDs), typically operated with constant-voltage or direct-current (DC) power sources, are candidates for next-generation solid-state lighting and displays, as they are light, thin, inexpensive, and flexible. However, researchers have focused mainly on the device itself (e.g., development of novel materials, design of the device structure, and optical outcoupling engineering), and little attention has been paid to the driving mode. Recently, an alternative concept to DC-driven OLEDs by directly driving devices using time-dependent voltages or alternating current (AC) has been explored. Here, the effects of different device structures of AC-driven OLEDs, for example, double-insulation, single-insulation, double-injection, and tandem structure, on the device performance are systematically investigated. The formation of excitons and the dielectric layer, which are important to achieve high-performance AC-driven OLEDs, are carefully considered. The importance of gaining further understanding of the fundamental properties of AC-driven OLEDs is then discussed, especially as they relate to device physics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis and Control of Pulse-Width Modulated AC to DC Voltage Source Converters.

NASA Astrophysics Data System (ADS)

Wu, Rusong

The pulse width modulated AC to DC voltage source converter is comprehensively analyzed in the thesis. A general mathematical model of the converter is first established, which is discontinuous, time-variant and non-linear. The following three techniques are used to obtain closed form solutions: Fourier analysis, transformation of reference frame and small signal linearization. Three models, namely, a steady-state DC model, a low frequency small signal AC model and a high frequency model, are consequently developed. Finally, three solution sets, namely, the steady-state solution, various dynamic transfer functions and the high frequency harmonic components, are obtained from the three models. Two control strategies, the Phase and Amplitude Control (PAC) and a new proposed strategy, Predicted Current Control with a Fixed Switching Frequency (PCFF), are investigated. Based on the transfer functions derived from the above mentioned analysis, regulators for a closed-loop control are designed. A prototype circuit is built to experimentally verify the theoretical predictions. The analysis and experimental results show that both strategies produce nearly sinusoidal line current with unity power factor on the utility side in both rectifying and regenerating operations and concurrently provide a regulated DC output voltage on the load side. However the proposed PCFF control has a faster and improved dynamic response over the PAC control. Moreover it is also easier to be implemented. Therefore, the PCFF control is preferable to the PAC control. As an example of application, a configuration of variable DC supply under PCFF control is proposed. The quasi-optimal dynamic response obtained shows that the PWM AC to DC converter lays the foundation for building a four-quadrant, fast-dynamic system, and the PCFF control is an effective strategy for improving dynamic performances not only as applied to the AC to DC converter, but also as applied to the DC to DC chopper or other circuits.

Multiple high voltage output DC-to-DC power converter

NASA Technical Reports Server (NTRS)

Cronin, Donald L. (Inventor); Farber, Bertrand F. (Inventor); Gehm, Hartmut K. (Inventor); Goldin, Daniel S. (Inventor)

1977-01-01

Disclosed is a multiple output DC-to-DC converter. The DC input power is filtered and passed through a chopper preregulator. The chopper output is then passed through a current source inverter controlled by a squarewave generator. The resultant AC is passed through the primary winding of a transformer, with high voltages induced in a plurality of secondary windings. The high voltage secondary outputs are each solid-state rectified for passage to individual output loads. Multiple feedback loops control the operation of the chopper preregulator, one being responsive to the current through the primary winding and another responsive to the DC voltage level at a selected output.

Dynamic Performance of a Back-to-Back HVDC Station Based on Voltage Source Converters

NASA Astrophysics Data System (ADS)

Khatir, Mohamed; Zidi, Sid-Ahmed; Hadjeri, Samir; Fellah, Mohammed-Karim

2010-01-01

The recent developments in semiconductors and control equipment have made the voltage source converter based high voltage direct current (VSC-HVDC) feasible. This new DC transmission is known as "HVDC Light or "HVDC Plus by leading vendors. Due to the use of VSC technology and pulse width modulation (PWM) the VSC-HVDC has a number of potential advantages as compared with classic HVDC. In this paper, the scenario of back-to-back VSC-HVDC link connecting two adjacent asynchronous AC networks is studied. Control strategy is implemented and its dynamic performances during disturbances are investigated in MATLAB/Simulink program. The simulation results have shown good performance of the proposed system under balanced and unbalanced fault conditions.

Ferroresonant flux coupled battery charger

NASA Technical Reports Server (NTRS)

McLyman, Colonel W. T. (Inventor)

1987-01-01

A battery charger for incorporation into an electric-powered vehicle is disclosed. The charger includes a ferroresonant voltage-regulating circuit for providing an output voltage proportional to the frequency of an input AC voltage. A high frequency converter converts a DC voltage supplied, for example, from a rectifier connected to a standard AC outlet, to a controlled frequency AC voltage which is supplied to the input of the ferroresonant circuit. The ferroresonant circuit includes an output, a saturable core transformer connected across the output, and a first linear inductor and a capacitor connected in series across the saturable core transformer and tuned to resonate at the third harmonic of the AC voltage from the high frequency converter. The ferroresonant circuit further includes a second linear inductor connected between the input of the ferroresonant circuit and the saturable core transformer. The output voltage from the ferroresonant circuit is rectified and applied across a pair of output terminals adapted to be connected to the battery to be charged. A feedback circuit compares the voltage across the output terminals with a reference voltage and controls the frequency of the AC voltage produced by the high frequency converter to maintain the voltage across the output terminals at a predetermined value. The second linear inductor provides a highly reactive load in the event of a fault across the output terminals to render the charger short-circuit proof.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

NASA Astrophysics Data System (ADS)

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf, Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

PubMed Central

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf , Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning. PMID:28053312

System and method for monitoring and controlling stator winding temperature in a de-energized AC motor

DOEpatents

Lu, Bin [Kenosha, WI; Luebke, Charles John [Sussex, WI; Habetler, Thomas G [Snellville, GA; Zhang, Pinjia [Atlanta, GA; Becker, Scott K [Oak Creek, WI

2011-12-27

A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.

Modeling development of converter topologies and control for BTB voltage source converters. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, L.

1998-08-01

This report presents the results of an investigation into the merits of using a back-to-back voltage source converter (BTB-VSC) as an alternative to a conventional back-to-back high voltage DC link (HVDC). The report presents the basic benefits of the new technology along with the basic control blocks needed to implement the design. The report also describes a model of the BTB-VSC implemented in EMTDC{trademark} and discusses the use of the model. Simulation results, showing how the model responds to various control actions and system disturbances, are presented. This modeling work developed a detailed EMTDC{trademark} model using the appropriate converter technologymore » and magnetic interface configuration. Various possible converter and magnetic interface configurations were examined and the most promising configuration was used for the model. The chosen configuration minimizes the number of high voltage transformers needed and minimizes the complexity non-standard interfacing transformers. There is no need for transformers with phase shifts other than zero or thirty degrees (wye-wye or wye-delta). The only non-standard feature is the necessity of bringing the neutral side of the high voltage winding on the wye-wye unit out through bushings and to insulate the wye-wye transformer for the system voltage which is twice the transformer winding voltage. The developed EMTDC{trademark} model was used to demonstrate the possibility of achieving independent control of the real power transmitted and the voltages at the AC terminals. The model also demonstrates the ability to interconnect weak AC systems without the necessity of additional voltage support equipment as is the case with the conventional back-to-back DC interconnection. The model has been shown to work with short circuit ratios less than 2 based on the total rating of the high voltage transformers.« less

Study of the generator/motor operation of induction machines in a high frequency link space power system

NASA Technical Reports Server (NTRS)

Lipo, Thomas A.; Sood, Pradeep K.

1987-01-01

Static power conversion systems have traditionally utilized dc current or voltage source links for converting power from one ac or dc form to another since it readily achieves the temporary energy storage required to decouple the input from the output. Such links, however, result in bulky dc capacitors and/or inductors and lead to relatively high losses in the converters due to stresses on the semiconductor switches. The feasibility of utilizing a high frequency sinusoidal voltage link to accomplish the energy storage and decoupling function is examined. In particular, a type of resonant six pulse bridge interface converter is proposed which utilizes zero voltage switching principles to minimize switching losses and uses an easy to implement technique for pulse density modulation to control the amplitude, frequency, and the waveshape of the synthesized low frequency voltage or current. Adaptation of the proposed topology for power conversion to single-phase ac and dc voltage or current outputs is shown to be straight forward. The feasibility of the proposed power circuit and control technique for both active and passive loads are verified by means of simulation and experiment.

Differences between direct current and alternating current capacitance nonlinearities in high-k dielectrics and their relation to hopping conduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaldi, O.; Kassmi, M.; El Manar University, LMOP, 2092 Tunis

2014-08-28

Capacitance nonlinearities were studied in atomic layer deposited HfO{sub 2} films using two types of signals: a pure ac voltage of large magnitude (ac nonlinearities) and a small ac voltage superimposed to a large dc voltage (dc nonlinearities). In theory, ac and dc nonlinearities should be of the same order of magnitude. However, in practice, ac nonlinearities are found to be an order of magnitude higher than dc nonlinearities. Besides capacitance nonlinearities, hopping conduction is studied using low-frequency impedance measurements and is discussed through the correlated barrier hopping model. The link between hopping and nonlinearity is established. The ac nonlinearitiesmore » are ascribed to the polarization of isolated defect pairs, while dc nonlinearities are attributed to electrode polarization which originates from defect percolation paths. Both the ac and dc capacitance nonlinearities display an exponential variation with voltage, which results from field-induced lowering of the hopping barrier energy.« less

Triple Hybrid Energy Harvesting Interface Electronics

NASA Astrophysics Data System (ADS)

Uluşan, H.; Chamanian, S.; Pathirana, W. M. P. R.; Zorlu, Ö.; Muhtaroğlu, A.; Külah, H.

2016-11-01

This study presents a novel triple hybrid system that combines simultaneously generated power from thermoelectric (TE), vibration-based electromagnetic (EM) and piezoelectric (PZT) harvesters for a relatively high power supply capability. In the proposed solution each harvesting source utilizes a distinct power management circuit that generates a DC voltage suitable for combining the three parallel supplies. The circuits are designed and implemented in 180 nm standard CMOS technology, and are terminated with a schottky diode to avoid reverse current flow. The harvested AC signal from the EM harvester is rectified with a self-powered AC-DC doubler, which utilizes active diode structures to minimize the forward- bias voltage drop. The PZT interface electronics utilizes a negative voltage converter as the first stage, followed by synchronous power extraction and DC-to-DC conversion through internal switches, and an external inductor. The ultra-low voltage DC power harvested by the TE generator is stepped up through a charge-pump driven by an LC oscillator with fully- integrated center-tapped differential inductors. Test results indicate that hybrid energy harvesting circuit provides more than 1 V output for load resistances higher than 100 kΩ (10 μW) where the stand-alone harvesting circuits are not able to reach 1 V output. This is the first hybrid harvester circuit that simultaneously extracts energy from three independent sources, and delivers a single DC output.

Modularized multilevel and z-source power converter as renewable energy interface for vehicle and grid-connected applications

NASA Astrophysics Data System (ADS)

Cao, Dong

Due the energy crisis and increased oil price, renewable energy sources such as photovoltaic panel, wind turbine, or thermoelectric generation module, are used more and more widely for vehicle and grid-connected applications. However, the output of these renewable energy sources varies according to different solar radiation, wind speed, or temperature difference, a power converter interface is required for the vehicle or grid-connected applications. Thermoelectric generation (TEG) module as a renewable energy source for automotive industry is becoming very popular recently. Because of the inherent characteristics of TEG modules, a low input voltage, high input current and high voltage gain dc-dc converters are needed for the automotive load. Traditional high voltage gain dc-dc converters are not suitable for automotive application in terms of size and high temperature operation. Switched-capacitor dc-dc converters have to be used for this application. However, high voltage spike and EMI problems exist in traditional switched-capacitor dc-dc converters. Huge capacitor banks have to be utilized to reduce the voltage ripple and achieve high efficiency. A series of zero current switching (ZCS) or zero voltage switching switched-capacitor dc-dc converters have been proposed to overcome the aforementioned problems of the traditional switched-capacitor dc-dc converters. By using the proposed soft-switching strategy, high voltage spike is reduced, high EMI noise is restricted, and the huge capacitor bank is eliminated. High efficiency, high power density and high temperature switched-capacitor dc-dc converters could be made for the TEG interface in vehicle applications. Several prototypes have been made to validate the proposed circuit and confirm the circuit operation. In order to apply PV panel for grid-connected application, a low cost dc-ac inverter interface is required. From the use of transformer and safety concern, two different solutions can be implemented, non-isolated or isolated PV inverter. For the non-isolated transformer-less solution, a semi-Z-source inverter for single phase photovoltaic systems has been proposed. The proposed semi-Z-source inverter utilizes only two switching devices with doubly grounded feature. The total cost have been reduced, the safety and EMI issues caused by the high frequency ground current are solved. For the transformer isolated solution, a boost half-bridge dc-ac micro-inverter has been proposed. The proposed boost half-bridge dc-dc converter utilizes only two switching devices with zero voltage switching features which is able to reduce the total system cost and power loss.

A Generalised Fault Protection Structure Proposed for Uni-grounded Low-Voltage AC Microgrids

NASA Astrophysics Data System (ADS)

Bui, Duong Minh; Chen, Shi-Lin; Lien, Keng-Yu; Jiang, Jheng-Lun

2016-04-01

This paper presents three main configurations of uni-grounded low-voltage AC microgrids. Transient situations of a uni-grounded low-voltage (LV) AC microgrid (MG) are simulated through various fault tests and operation transition tests between grid-connected and islanded modes. Based on transient simulation results, available fault protection methods are proposed for main and back-up protection of a uni-grounded AC microgrid. In addition, concept of a generalised fault protection structure of uni-grounded LVAC MGs is mentioned in the paper. As a result, main contributions of the paper are: (i) definition of different uni-grounded LVAC MG configurations; (ii) analysing transient responses of a uni-grounded LVAC microgrid through line-to-line faults, line-to-ground faults, three-phase faults and a microgrid operation transition test, (iii) proposing available fault protection methods for uni-grounded microgrids, such as: non-directional or directional overcurrent protection, under/over voltage protection, differential current protection, voltage-restrained overcurrent protection, and other fault protection principles not based on phase currents and voltages (e.g. total harmonic distortion detection of currents and voltages, using sequence components of current and voltage, 3I0 or 3V0 components), and (iv) developing a generalised fault protection structure with six individual protection zones to be suitable for different uni-grounded AC MG configurations.

Three-phase Four-leg Inverter LabVIEW FPGA Control Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

In the area of power electronics control, Field Programmable Gate Arrays (FPGAs) have the capability to outperform their Digital Signal Processor (DSP) counterparts due to the FPGA’s ability to implement true parallel processing and therefore facilitate higher switching frequencies, higher control bandwidth, and/or enhanced functionality. National Instruments (NI) has developed two platforms, Compact RIO (cRIO) and Single Board RIO (sbRIO), which combine a real-time processor with an FPGA. The FPGA can be programmed with a subset of the well-known LabVIEW graphical programming language. The use of cRIO and sbRIO for power electronics control has developed over the last few yearsmore » to include control of three-phase inverters. Most three-phase inverter topologies include three switching legs. The addition of a fourth-leg to natively generate the neutral connection allows the inverter to serve single-phase loads in a microgrid or stand-alone power system and to balance the three-phase voltages in the presence of significant load imbalance. However, the control of a four-leg inverter is much more complex. In particular, instead of standard two-dimensional space vector modulation (SVM), the inverter requires three-dimensional space vector modulation (3D-SVM). The candidate software implements complete control algorithms in LabVIEW FPGA for a three-phase four-leg inverter. The software includes feedback control loops, three-dimensional space vector modulation gate-drive algorithms, advanced alarm handling capabilities, contactor control, power measurements, and debugging and tuning tools. The feedback control loops allow inverter operation in AC voltage control, AC current control, or DC bus voltage control modes based on external mode selection by a user or supervisory controller. The software includes the ability to synchronize its AC output to the grid or other voltage-source before connection. The software also includes provisions to allow inverter operation in parallel with other voltage regulating devices on the AC or DC buses. This flexibility allows the Inverter to operate as a stand-alone voltage source, connected to the grid, or in parallel with other controllable voltage sources as part of a microgrid or remote power system. In addition, as the inverter is expected to operate under severe unbalanced conditions, the software includes algorithms to accurately compute real and reactive power for each phase based on definitions provided in the IEEE Standard 1459: IEEE Standard Definitions for the Measurement of Electric Power Quantities Under Sinusoidal, Nonsinusoidal, Balanced, or Unbalanced Conditions. Finally, the software includes code to output analog signals for debugging and for tuning of control loops. The software fits on the Xilinx Virtex V LX110 FPGA embedded in the NI cRIO-9118 FPGA chassis, and with a 40 MHz base clock, supports a modulation update rate of 40 MHz, user-settable switching frequencies and synchronized control loop update rates of tens of kHz, and reference waveform generation, including Phase Lock Loop (PLL), update rate of 100 kHz.« less

A new mathematical model and control of a three-phase AC-DC voltage source converter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blasko, V.; Kaura, V.

1997-01-01

A new mathematical model of the power circuit of a three-phase voltage source converter (VSC) was developed in the stationary and synchronous reference frames. The mathematical model was then used to analyze and synthesize the voltage and current control loops for the VSC. Analytical expressions were derived for calculating the gains and time constants of the current and voltage regulators. The mathematical model was used to control a 140-kW regenerative VSC. The synchronous reference frame model was used to define feedforward signals in the current regulators to eliminate the cross coupling between the d and q phases. It allowed themore » reduction of the current control loop to first-order plants and improved their tracking capability. The bandwidths of the current and voltage-control loops were found to be approximately 20 and 60 times (respectively) smaller than the sampling frequency. All control algorithms were implemented in a digital-signal processor. All results of the analysis were experimentally verified.« less

Comparison of direct current and 50 Hz alternating current microscopic corona characteristics on conductors

NASA Astrophysics Data System (ADS)

Zhang, Shuai; Zhang, Bo; He, Jinliang

2014-06-01

Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and AC coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.

A new infusion pathway intactness monitoring system.

PubMed

Ogawa, Hidekuni; Yonezawa, Yoshiharu; Maki, Hiromichi; Ninomiya, Ishio; Sata, Koji; Hamada, Shingo; Caldwell, W Morton

2006-01-01

A new infusion pathway monitoring system has been developed for hospital and home use. The system consists of linear integrated circuits and a low-power 8-bit single chip microcomputer which constantly monitors the infusion pathway intactness. An AC (alternating current) voltage is induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. The induced AC voltage can be recorded by a main electrode wrapped around the infusion polyvinyl chloride tube. A reference electrode is wrapped on the electrode to monitor the AC voltage around the main electrode. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltages and alerts the nursing station, via the nurse call system or PHS (personal handy phone system).

Power inversion design for ocean wave energy harvesting

NASA Astrophysics Data System (ADS)

Talebani, Anwar N.

The needs for energy sources are increasing day by day because of several factors, such as oil depletion, and global climate change due to the higher level of CO2, so the exploration of various renewable energy sources is very promising area of study. The available ocean waves can be utilized as free source of energy as the water covers 70% of the earth surface. This thesis presents the ocean wave energy as a source of renewable energy. By addressing the problem of designing efficient power electronics system to deliver 5 KW from the induction generator to the grid with less possible losses and harmonics as possible and to control current fed to the grid to successfully harvest ocean wave energy. We design an AC-DC full bridge rectifier converter, and a DC-DC boost converter to harvest wave energy from AC to regulated DC. In order to increase the design efficiency, we need to increase the power factor from (0.5-0.6) to 1. This is accomplished by designing the boost converter with power factor correction in continues mode with RC circuit as an input to the boost converter power factor correction. This design results in a phase shift between the input current and voltage of the full bridge rectifier to generate a small reactive power. The reactive power is injected to the induction generator to maintain its functionality by generating a magnetic field in its stator. Next, we design a single-phase pulse width modulator full bridge voltage source DC-AC grid-tied mode inverter to harvest regulated DC wave energy to AC. The designed inverter is modulated by inner current loop, to control current injected to the grid with minimal filter component to maintain power quality at the grid. The simulation results show that our design successfully control the current level fed to the grid. It is noteworthy that the simulated efficiency is higher than the calculated one since we used an ideal switch in the simulated circuit.

System and method for motor speed estimation of an electric motor

DOEpatents

Lu, Bin [Kenosha, WI; Yan, Ting [Brookfield, WI; Luebke, Charles John [Sussex, WI; Sharma, Santosh Kumar [Viman Nagar, IN

2012-06-19

A system and method for a motor management system includes a computer readable storage medium and a processing unit. The processing unit configured to determine a voltage value of a voltage input to an alternating current (AC) motor, determine a frequency value of at least one of a voltage input and a current input to the AC motor, determine a load value from the AC motor, and access a set of motor nameplate data, where the set of motor nameplate data includes a rated power, a rated speed, a rated frequency, and a rated voltage of the AC motor. The processing unit is also configured to estimate a motor speed based on the voltage value, the frequency value, the load value, and the set of nameplate data and also store the motor speed on the computer readable storage medium.

A Passive EMI Filter with Access to the Ungrounded Motor Neutral Line-The Case that a General-Purpose Inverter is Directly Connected to a Three-Phase Grounded Voltage Source-

NASA Astrophysics Data System (ADS)

Doumoto, Takafumi; Akagi, Hirofumi

This paper proposes a small-sized passive EMI filter for the purpose of eliminating high-frequency shaft voltage and ground leakage current from an ac motor. The motor is driven by a general-purpose PWM inverter connected to a three-phase grounded voltage source. The passive EMI filter requires access to the ungrounded neutral point of the motor. This unique circuit configuration makes the common-mode inductor effective in reducing the high-frequency common-mode voltage generated by the PWM inverter with a carrier frequency of 15kHz. As a result, both high-frequency shaft voltage and ground leakage current can be eliminated very efficiently. However, the common-mode inductor may not play any role in reducing the low-frequency common-mode voltage generated by the diode rectifier, so that a low-frequency component still remains in the shaft voltage. Such a low-frequency shaft voltage may not produce any bad effect on motor bearings. The validity and effectiveness of the EMI filter is verified by experimental results obtained from a 200-V 5-kVA laboratory system.

Very low noise AC/DC power supply systems for large detector arrays.

PubMed

Arnaboldi, C; Baù, A; Carniti, P; Cassina, L; Giachero, A; Gotti, C; Maino, M; Passerini, A; Pessina, G

2015-12-01

In this work, we present the first part of the power supply system for the CUORE and LUCIFER arrays of bolometric detectors. For CUORE, it consists of AC/DC commercial power supplies (0-60 V output) followed by custom DC/DC modules (48 V input, ±5 V to ±13.5 V outputs). Each module has 3 floating and independently configurable output voltages. In LUCIFER, the AC/DC + DC/DC stages are combined into a commercial medium-power AC/DC source. At the outputs of both setups, we introduced filters with the aim of lowering the noise and to protect the following stages from high voltage spikes that can be generated by the energy stored in the cables after the release of accidental short circuits. Output noise is very low, as required: in the 100 MHz bandwidth the RMS level is about 37 μV(RMS) (CUORE setup) and 90 μV(RMS) (LUCIFER setup) at a load of 7 A, with a negligible dependence on the load current. Even more importantly, high frequency switching disturbances are almost completely suppressed. The efficiency of both systems is above 85%. Both systems are completely programmable and monitored via CAN bus (optically coupled).

Module Two: Voltage; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

In this module the student will study and learn what voltage is, how it is generated, what AC (alternating current) and DC (direct current) are and why both kinds are needed, and how to measure voltages. The module is divided into six lessons: EMF (electromotive force) from chemical action, magnetism, electromagnetic induction, AC voltage, the…

Electric Drive Study. Volume 1

DTIC Science & Technology

1987-12-21

CONDITIONER HIGH VOLTAGE DC ICONDITIONER 3 ,300-50 VOLT5), dCONTROL! Figure 5-4. Typical AC Drive System 20 system usable with an induction motor. The...controlling component in an AC drive is the motor power conditioner . This component changes the high voltage DC power to controlled AC power of...selected voltage and frequency which is applied to the drive motors. Since the vehicle gains stored energy as it is accelerated, the motor power conditioner

Integration of offshore wind farms through high voltage direct current networks

NASA Astrophysics Data System (ADS)

Livermore, Luke

The integration of offshore wind farms through Multi Terminal DC (MTDC) networks into the GB network was investigated. The ability of Voltage Source Converter (VSC) High Voltage Direct Current (HVDC) to damp Subsynchronous Resonance (SSR) and ride through onshore AC faults was studied. Due to increased levels of wind generation in Scotland, substantial onshore and offshore reinforcements to the GB transmission network are proposed. Possible inland reinforcements include the use of series compensation through fixed capacitors. This potentially can lead to SSR. Offshore reinforcements are proposed by two HVDC links. In addition to its primary functions of bulk power transmission, a HVDC link can be used to provide damping against SSR, and this function has been modelled. Simulation studies have been carried out in PSCAD. In addition, a real-time hardware-in-the-loop HVDC test rig has been used to implement and validate the proposed damping scheme on an experimental platform. When faults occur within AC onshore networks, offshore MTDC networks are vulnerable to DC overvoltages, potentially damaging the DC plant and cables. Power reduction and power dissipation control systems were investigated to ride through onshore AC faults. These methods do not require dedicated fast communication systems. Simulations and laboratory experiments are carried out to evaluate the control systems, with the results from the two platforms compared..

Recovery of consciousness in broilers following combined dc and ac stunning

USDA-ARS?s Scientific Manuscript database

Broilers in the United States are typically electrically stunned using low voltage-high frequency pulsed DC water bath stunners and in the European Union broilers are electrocuted using high voltage-low frequency AC. DC stunned broilers regain consciousness in the absence of exsanguination and AC st...

An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Litzenberger, Wayne; Lava, Val

1994-08-01

References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

Membrane Pump for Synthetic Muscle Actuation

DTIC Science & Technology

2009-09-28

FIG. 3 is a schematic representation of an embodiment of a muscle equipped to use electroosmotic flow in accordance with the present invention...water through the membrane to the cathode. This movement of water across the membrane during the application of current is called electroosmotic ...current and a 120 V AC source, again with an appropriate electronics package to control voltage and current. Preferably, the power source 316 can be

Modeling and control of fuel cell based distributed generation systems

NASA Astrophysics Data System (ADS)

Jung, Jin Woo

This dissertation presents circuit models and control algorithms of fuel cell based distributed generation systems (DGS) for two DGS topologies. In the first topology, each DGS unit utilizes a battery in parallel to the fuel cell in a standalone AC power plant and a grid-interconnection. In the second topology, a Z-source converter, which employs both the L and C passive components and shoot-through zero vectors instead of the conventional DC/DC boost power converter in order to step up the DC-link voltage, is adopted for a standalone AC power supply. In Topology 1, two applications are studied: a standalone power generation (Single DGS Unit and Two DGS Units) and a grid-interconnection. First, dynamic model of the fuel cell is given based on electrochemical process. Second, two full-bridge DC to DC converters are adopted and their controllers are designed: an unidirectional full-bridge DC to DC boost converter for the fuel cell and a bidirectional full-bridge DC to DC buck/boost converter for the battery. Third, for a three-phase DC to AC inverter without or with a Delta/Y transformer, a discrete-time state space circuit model is given and two discrete-time feedback controllers are designed: voltage controller in the outer loop and current controller in the inner loop. And last, for load sharing of two DGS units and power flow control of two DGS units or the DGS connected to the grid, real and reactive power controllers are proposed. Particularly, for the grid-connected DGS application, a synchronization issue between an islanding mode and a paralleling mode to the grid is investigated, and two case studies are performed. To demonstrate the proposed circuit models and control strategies, simulation test-beds using Matlab/Simulink are constructed for each configuration of the fuel cell based DGS with a three-phase AC 120 V (L-N)/60 Hz/50 kVA and various simulation results are presented. In Topology 2, this dissertation presents system modeling, modified space vector PWM implementation (MSVPWM) and design of a closed-loop controller of the Z-source converter which utilizes L and C components and shoot-through zero vectors for the standalone AC power generation. The fuel cell system is modeled by an electrical R-C circuit in order to include slow dynamics of the fuel cells and a voltage-current characteristic of a cell is also considered. A discrete-time state space model is derived to implement digital control and a space vector pulse-width modulation (SVPWM) technique is modified to realize the shoot-through zero vectors that boost the DC-link voltage. Also, three discrete-time feedback controllers are designed: a discrete-time optimal voltage controller, a discrete-time sliding mode current controller, and a discrete-time PI DC-link voltage controller. Furthermore, an asymptotic observer is used to reduce the number of sensors and enhance the reliability of the system. To demonstrate the analyzed circuit model and proposed control strategy, various simulation results using Matlab/Simulink are presented under both light/heavy loads and linear/nonlinear loads for a three-phase AC 208 V (L-L)/60 Hz/10 kVA.

Fuzzy Logic Controlled Solar Module for Driving Three- Phase Induction Motor

NASA Astrophysics Data System (ADS)

Afiqah Zainal, Nurul; Sooi Tat, Chan; Ajisman

2016-02-01

Renewable energy produced by solar module gives advantages for generated three- phase induction motor in remote area. But, solar module's ou tput is uncertain and complex. Fuzzy logic controller is one of controllers that can handle non-linear system and maximum power of solar module. Fuzzy logic controller used for Maximum Power Point Tracking (MPPT) technique to control Pulse-Width Modulation (PWM) for switching power electronics circuit. DC-DC boost converter used to boost up photovoltaic voltage to desired output and supply voltage source inverter which controlled by three-phase PWM generated by microcontroller. IGBT switched Voltage source inverter (VSI) produced alternating current (AC) voltage from direct current (DC) source to control speed of three-phase induction motor from boost converter output. Results showed that, the output power of solar module is optimized and controlled by using fuzzy logic controller. Besides that, the three-phase induction motor can be drive and control using VSI switching by the PWM signal generated by the fuzzy logic controller. This concluded that the non-linear system can be controlled and used in driving three-phase induction motor.

AC Josephson effect without superconductivity, and other effects of radio frequency quantum nanoelectronics

NASA Astrophysics Data System (ADS)

Waintal, Xavier; Gaury, Benoit; Weston, Joseph

With single coherent electron sources and electronic interferometers now available in the lab, the time resolved dynamics of electrons can now be probed directly. I will discuss how a fast raise of voltage propagates inside an electronic interferometer and leads to an oscillating current of well controled frequency. This phenomena is the normal counterpart to the AC josephson effect. I will also briefly advertize our software for computing quantum transport properties, Kwant (http://kwant-project.org) and its time-dependent extension T-Kwant.

Helicopter-based live-line work. Volume 1, Helicopter platform work between phases: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gela, G.

1993-06-01

This report presents experimental data on tests of a configuration consisting of a helicopter between two energized phases (for AC and switching surge) or poles (for DC). The configuration is that related to live-line work from a hovering helicopter. The McDonnell Douglas 500 Series helicopter was used for the tests. All tests were performed with phase-to-phase, or pole-to-pole energization. For AC tests, proper relationship between the phase-to-ground voltages and the phase-to-phase voltage was maintained by energizing the experimental setup from a balanced 3-{phi} AC source. For DC tests, one pole was energized with positive DC voltage to ground, while themore » other pole was energized with negative DC voltage to ground. For switching surge tests, a surge of positive polarity and a specific peak voltage magnitude was applied to one phase while a surge of negative polarity and the same peak voltage Magnitude was simultaneously applied to the other phase, resulting in {alpha} = 0.5 ({alpha} is the ratio between negative and total surge). In the research program, four conditions were investigated, namely helicopter operating versus not operating, and helicopter bonded to one phase or pole versus not bonded. Results from this research show effects of the rotating main rotor blade of the helicopter, effect of the position of the electrically floating helicopter in the phase-to-phase or pole-to-pole gap, effects of the mannequin, importance of the polarity of the DC poles and switching surges, and effects of inclement weather such as rain. The overall conclusion of this research is that the phase-to-phase or pole-to-pole spacings that cause sparkover with the helicopter between phases (poles) were always significantly smaller than the typical spacings on actual existing overhead transmission lines of the corresponding voltage rating.« less

Three-Level 48-Pulse STATCOM with Pulse Width Modulation

NASA Astrophysics Data System (ADS)

Singh, Bhim; Srinivas, Kadagala Venkata

2016-03-01

In this paper, a new control strategy of a three-level 48-pulse static synchronous compensator (STATCOM) is proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. The proposed STATCOM is realized using eight units of three-level voltage source converters (VSCs) to form a three-level 48-pulse STATCOM. The conduction angle of each three-level VSC is modulated to control the ac converter output voltage, which controls the reactive power of the STATCOM. A fuzzy logic controller is used to control the STATCOM. The dynamic performance of the STATCOM is studied for the control of the reference reactive power, the reference terminal voltage and under the switching of inductive and capacitive loads.

Chance-Constrained AC Optimal Power Flow for Distribution Systems With Renewables

DOE Office of Scientific and Technical Information (OSTI.GOV)

DallAnese, Emiliano; Baker, Kyri; Summers, Tyler

This paper focuses on distribution systems featuring renewable energy sources (RESs) and energy storage systems, and presents an AC optimal power flow (OPF) approach to optimize system-level performance objectives while coping with uncertainty in both RES generation and loads. The proposed method hinges on a chance-constrained AC OPF formulation where probabilistic constraints are utilized to enforce voltage regulation with prescribed probability. A computationally more affordable convex reformulation is developed by resorting to suitable linear approximations of the AC power-flow equations as well as convex approximations of the chance constraints. The approximate chance constraints provide conservative bounds that hold for arbitrarymore » distributions of the forecasting errors. An adaptive strategy is then obtained by embedding the proposed AC OPF task into a model predictive control framework. Finally, a distributed solver is developed to strategically distribute the solution of the optimization problems across utility and customers.« less

Switch contact device for interrupting high current, high voltage, AC and DC circuits

DOEpatents

Via, Lester C.; Witherspoon, F. Douglas; Ryan, John M.

2005-01-04

A high voltage switch contact structure capable of interrupting high voltage, high current AC and DC circuits. The contact structure confines the arc created when contacts open to the thin area between two insulating surfaces in intimate contact. This forces the arc into the shape of a thin sheet which loses heat energy far more rapidly than an arc column having a circular cross-section. These high heat losses require a dramatic increase in the voltage required to maintain the arc, thus extinguishing it when the required voltage exceeds the available voltage. The arc extinguishing process with this invention is not dependent on the occurrence of a current zero crossing and, consequently, is capable of rapidly interrupting both AC and DC circuits. The contact structure achieves its high performance without the use of sulfur hexafluoride.

Effect of Dimension and Shape of Magnet on the Performance AC Generator with Translation Motion

NASA Astrophysics Data System (ADS)

Indriani, A.; Dimas, S.; Hendra

2018-02-01

The development of power plants using the renewable energy sources is very rapid. Renewable energy sources used solar energy, wind energy, ocean wave energy and other energy. All of these renewable energy sources require a processing device or a change of motion system to become electrical energy. One processing device is a generator which have work principle of converting motion (mechanical) energy into electrical energy with rotary shaft, blade and other motion components. Generator consists of several types of rotation motion and linear motion (translational). The generator have components such as rotor, stator and anchor. In the rotor and stator having magnet and winding coil as an electric generating part of the electric motion force. Working principle of AC generator with linear motion (translation) also apply the principle of Faraday that is using magnetic induction which change iron magnet to produce magnetic flux. Magnetic flux is captured by the stator to be converted into electrical energy. Linear motion generators consist of linear induction machine, wound synchronous machine field, and permanent magnet synchronous [1]. Performance of synchronous generator of translation motion is influenced by magnet type, magnetic shape, coil winding, magnetic and coil spacing and others. In this paper focus on the neodymium magnet with varying shapes, number of coil windings and gap of magnetic distances. This generator work by using pneumatic mechanism (PLTGL) for power plants system. Result testing of performance AC generator translation motion obtained that maximum voltage, current and power are 63 Volt for diameter winding coil 0.15 mm, number of winding coil 13000 and distance of magnet 20 mm. For effect shape of magnet, maximum voltage happen on rectangle magnet 30x20x5 mm with 4.64 Volt. Voltage and power on effect of diameter winding coil is 14.63 V and 17.82 W at the diameter winding coil 0.7 and number of winding coil is 1260 with the distance of magnet 25 mm.

Applying PWM to control overcurrents at unbalanced faults of force-commutated VSCs used as static var compensators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Y.; Ekstroem, A.

1997-01-01

This study is devoted to investigating the possibility of controlling the overcurrent of a forced-commutated voltage source converter (VSC) by PWM when the ac system is undergoing large unbalanced disturbance. The converter is supposed to be used as a static var compensator at a high power level. A novel control strategy is proposed for controlling the reactive current and the dc side voltage independently. Digital simulation results are presented and compared with the results by using just the reactive current control with fundamental switching frequency.

Comparison of direct current and 50 Hz alternating current microscopic corona characteristics on conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shuai, E-mail: zhangshuai94@gmail.com; Zhang, Bo, E-mail: shizbcn@mail.tsinghua.edu.cn; He, Jinliang, E-mail: hejl@tsinghua.edu.cn

Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and ACmore » coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.« less

Utilizing zero-sequence switchings for reversible converters

DOEpatents

Hsu, John S.; Su, Gui-Jia; Adams, Donald J.; Nagashima, James M.; Stancu, Constantin; Carlson, Douglas S.; Smith, Gregory S.

2004-12-14

A method for providing additional dc inputs or outputs (49, 59) from a dc-to-ac inverter (10) for controlling motor loads (60) comprises deriving zero-sequence components (V.sub.ao, V.sub.bo, and V.sub.co) from the inverter (10) through additional circuit branches with power switching devices (23, 44, 46), transforming the voltage between a high voltage and a low voltage using a transformer or motor (42, 50), converting the low voltage between ac and dc using a rectifier (41, 51) or an H-bridge (61), and providing at least one low voltage dc input or output (49, 59). The transformation of the ac voltage may be either single phase or three phase. Where less than a 100% duty cycle is acceptable, a two-phase modulation of the switching signals controlling the inverter (10) reduces switching losses in the inverter (10). A plurality of circuits for carrying out the invention are also disclosed.

Electrical tree initiation in polyethylene absorbing Penning gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimizu, N.; Tohyama, N.; Sato, H.

1996-12-31

Ac tree initiation voltage was examined in untreated LDPE, vacuum degassed LDPE and LDPE absorbing He gas (He gas was absorbed after vacuum degassing). The authors have already reported that vacuum degassed LDPE shows much higher tree initiation voltage than untreated one because of absence of oxygen. Therefore they expected that LDPE absorbing He shows the same property with vacuum degassed LDPE. However tree initiation voltage of LDPE absorbing He is as low as that of untreated LDPE. LDPE absorbing Ar gas shows the same tendency. He or Ar gas does not change so much impulse tree initiation voltage. LDPEmore » absorbing He was not well dyed with methylene blue after ac voltage application, which indicates that active oxidation does not occur. Low ac tree initiation voltage in LDPE absorbing He or Ar may be caused by Penning ionization in free volume.« less

Direct-current converter for gas-discharge lamps

NASA Technical Reports Server (NTRS)

Lutus, P.

1980-01-01

Metal/halide and similar gas-discharge lamps are powered from low-voltage dc source using small efficient converter. Converter is useful whenever 60-cycle ac power is not available or where space and weight allocations are limited. Possible applications are offshore platforms, mobile homes, and emergency lighting. Design innovations give supply high reliability and efficiency up to 75 percent.

Characterization on performance of micromixer using DC-biased AC electroosmosis

NASA Astrophysics Data System (ADS)

Park, Bi-O.; Song, Simon

2010-11-01

An active micromixer using DC-biased AC-Electroosmosis (ACEO) is investigated to figure out the effects of design parameters on the mixing performance. The mixer consists of a straight microchannel, with a cross section of 60 x 100 μm, and gold electrode pairs fabricated in the microchannel. The design parameters include the number of electrode pairs, flow rate, DC-biased voltage, AC voltage and AC frequency. First, we found that a mixing index became 80% 100 μm downstream of a single electrode pair with a length of 2 mm when applying a 25Vpp, 2.0 VDC, 100 kHz sine signal to the electrodes. With decreasing AC frequency, the mixing index is affected little. But the mixing index significantly increases with increasing either DC-biased voltage or AC voltage. Also, we were able to increase the mixing index up to 90% by introducing alternating vortices with multiple electrode pairs. Finally, we discovered that the mixing index decreases as the flow rate increases in the microchannel, and there is an optimal number of electrode pairs with respect to a flow rate. Detailed quantitative measurement results will be presented at the meeting.

New Insulation Constructions for Aerospace Wiring Applications. Volume 1. Testing and Evaluation

DTIC Science & Technology

1991-06-01

28 S.3.2 CORONA INCEPTION AND EXTINCIION VOLTAGES 5 - 33 5.3.2.. AC CORONA INCEPTION AND EXTINCTION VOLTAGES 5...... - 33 5.3.2.2 DC CORONA ...SETUP ....... .. 5 - 27 5.10 DIELECTRIC CONSTANT TEST RESULTS .......... .. 5 - 32 5.11 AC CORONA INCEPTION AND EXTINCTION TEST, 22 AWG, 8.6 MIL WALL...AIRFRAME WIRE ... .......... 5 - 39 5.12 AC CORONA INCEPTION AND EXTINCTION TEST, 22 AWG, 5.8 MIL WALL, HOOK UP WIRE .... ........... 5 - 40 5.13 AC

Alternating current long range alpha particle detector

DOEpatents

MacArthur, Duncan W.; McAtee, James L.

1993-01-01

An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Alternating current long range alpha particle detector

DOEpatents

MacArthur, D.W.; McAtee, J.L.

1993-02-16

An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Impact of alternative electrical stunning parameters on the ability of broilers to recover consciousness and meat quality

USDA-ARS?s Scientific Manuscript database

Broilers in the United States are typically electrically stunned using low voltage-high frequency (12-38V, =400Hz) DC or AC water bath stunners. In the European Union, however, broilers are required to be electrocuted using high voltage-low frequency (50-150V, 50-350Hz) AC. Low voltage stunned broil...

Generator voltage stabilisation for series-hybrid electric vehicles.

PubMed

Stewart, P; Gladwin, D; Stewart, J; Cowley, R

2008-04-01

This paper presents a controller for use in speed control of an internal combustion engine for series-hybrid electric vehicle applications. Particular reference is made to the stability of the rectified DC link voltage under load disturbance. In the system under consideration, the primary power source is a four-cylinder normally aspirated gasoline internal combustion engine, which is mechanically coupled to a three-phase permanent magnet AC generator. The generated AC voltage is subsequently rectified to supply a lead-acid battery, and permanent magnet traction motors via three-phase full bridge power electronic inverters. Two complementary performance objectives exist. Firstly to maintain the internal combustion engine at its optimal operating point, and secondly to supply a stable 42 V supply to the traction drive inverters. Achievement of these goals minimises the transient energy storage requirements at the DC link, with a consequent reduction in both weight and cost. These objectives imply constant velocity operation of the internal combustion engine under external load disturbances and changes in both operating conditions and vehicle speed set-points. An electronically operated throttle allows closed loop engine velocity control. System time delays and nonlinearities render closed loop control design extremely problematic. A model-based controller is designed and shown to be effective in controlling the DC link voltage, resulting in the well-conditioned operation of the hybrid vehicle.

Dynamic characteristics of corona discharge generated under rainfall condition on AC charged conductors

NASA Astrophysics Data System (ADS)

Xu, Pengfei; Zhang, Bo; Wang, Zezhong; Chen, Shuiming; He, Jinliang

2017-12-01

By synchronous measurement of corona current and the water droplet deformation process on a conductor surface, different types of corona discharge are visualized when AC voltage is applied on a line-ground electrode system. The corona characteristics are closely related to the applied voltage and water supply rate. With the increase of AC voltage, the positive Taylor cone discharge firstly appears and then disappears, replaced by the dripping and crashing discharge. Furthermore, the number of pulses in each pulse train increases with the increase of applied voltage. The mechanism of the transfer from the positive Taylor cone discharge to the dripping and crashing discharge is found to be related to the oscillation process of the water droplet. The water supply rate also has a great influence on the characteristics of corona currents. The number of positive pulse trains increases linearly when the water supply rate gets larger, leading to a higher audible noise and radio interference level from the AC corona, which is quite different from that of the DC corona. The difference between the AC and DC coronas under rainfall conditions is analyzed finally.

Comparison of high-voltage ac and pulsed operation of a surface dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Williamson, James M.; Trump, Darryl D.; Bletzinger, Peter; Ganguly, Biswa N.

2006-10-01

A surface dielectric barrier discharge (DBD) in atmospheric pressure air was excited either by low frequency (0.3-2 kHz) high-voltage ac or by short, high-voltage pulses at repetition rates from 50 to 600 pulses s-1. The short-pulse excited discharge was more diffuse and did not have the pronounced bright multiple cathode spots observed in the ac excited discharge. The discharge voltage, current and average power deposited into the discharge were calculated for both types of excitation. As a measure of plasma-chemical efficiency, the ozone number density was measured by UV absorption as a function of average deposited power. The density of ozone produced by ac excitation did not increase so rapidly as that produced by short-pulse excitation as a function of average power, with a maximum measured density of ~3 × 1015 cm-3 at 25 W. The maximum ozone production achieved by short-pulse excitation was ~8.5 × 1015 cm-3 at 20 W, which was four times greater than that achieved by ac excitation at the same power level.

Noise-Optimized Silicon Radiometers

PubMed Central

Eppeldauer, George P.

2000-01-01

This paper describes a new, experimentally verified, noise analysis and the design considerations of the dynamic characteristics of silicon radiometers. Transimpedance gain, loop gain, and voltage gain were optimized versus frequency for photodiode current meters measuring ac and dc optical radiation. Silicon radiometers with improved dynamic characteristics were built and tested. The frequency-dependent photocurrent gains were measured. The noise floor was optimized in an ac measurement mode using photodiodes of different shunt resistance and operational amplifiers with low 1/f voltage and current noise. In the dark (without any signal), the noise floor of the optimized silicon radiometers was dominated by the Johnson noise of the source resistance. The Johnson noise was decreased and equalized to the amplified 1/f input noise at a 9 Hz chopping frequency and 30 s integration time constant, resulting in an equivalent root-mean-square (rms) photocurrent noise of 8 × 10−17 A. The lowest noise floor of 5 × 10−17 A, equal to a noise equivalent power (NEP) of 1.4 × 10−16 W at the 730 nm peak responsivity, was obtained at a 100 s integration time constant. The radiometers, optimized for ac measurements, were tested in a dc measurement mode as well. Performances in ac and dc measurement modes were compared. In the ac mode, a ten times shorter (40 s) overall measurement time was needed than in the dc mode (400 s) to obtain the same 10−16 A noise floor. PMID:27551606

Control of power to an inductively heated part

DOEpatents

Adkins, Douglas R.; Frost, Charles A.; Kahle, Philip M.; Kelley, J. Bruce; Stanton, Suzanne L.

1997-01-01

A process for induction hardening a part to a desired depth with an AC signal applied to the part from a closely coupled induction coil includes measuring the voltage of the AC signal at the coil and the current passing through the coil; and controlling the depth of hardening of the part from the measured voltage and current. The control system determines parameters of the part that are functions of applied voltage and current to the induction coil, and uses a neural network to control the application of the AC signal based on the detected functions for each part.

Control of power to an inductively heated part

DOEpatents

Adkins, D.R.; Frost, C.A.; Kahle, P.M.; Kelley, J.B.; Stanton, S.L.

1997-05-20

A process for induction hardening a part to a desired depth with an AC signal applied to the part from a closely coupled induction coil includes measuring the voltage of the AC signal at the coil and the current passing through the coil; and controlling the depth of hardening of the part from the measured voltage and current. The control system determines parameters of the part that are functions of applied voltage and current to the induction coil, and uses a neural network to control the application of the AC signal based on the detected functions for each part. 6 figs.

AC Loss Measurements on a 2G YBCO Coil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

2011-01-01

The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype highmore » voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.« less

AC/DC Smart Control And Power Sharing of DC Distribution Systems

DTIC Science & Technology

2012-02-10

system losses will decrease since the semiconductor losses due to switching in converter are reduced. The use of DC power systems to supply...cells yield variable DC voltage. In stand-alone systems , in order to be able to make full use of the generated power and to feed the loads, a controlled...alternate sources connected to the DC Distribution System

Single stage AC-DC converter for Galfenol-based micro-power energy harvesters

NASA Astrophysics Data System (ADS)

Cavaroc, Peyton; Curtis, Chandra; Naik, Suketu; Cooper, James

2014-06-01

Military based sensor systems are often hindered in operational deployment and/or other capabilities due to limitations in their energy storage elements. Typically operating from lithium based batteries, there is a finite amount of stored energy which the sensor can use to collect and transmit data. As a result, the sensors have reduced sensing and transmission rates. However, coupled with the latest advancements in energy harvesting, these sensors could potentially operate at standard sensing and transition rates as well as dramatically extend lifetimes. Working with the magnetostrictive material Galfenol, we demonstrate the production of enough energy to supplement and recharge a solid state battery thereby overcoming the deficiencies faced by unattended sensors. As with any vibration-based energy harvester, this solution produces an alternating current which needs to be rectified and boosted to a level conducive to recharge the storage element. This paper presents a power converter capable of efficiently converting an ultra-low AC voltage to a solid state charging voltage of 4.1VDC. While we are working with Galfenol transducers as our energy source, this converter may also be applied with any AC producing energy harvester, particularly at operating levels less than 2mW and 200mVAC.

Generalization of the Child-Langmuir law to the alternate extraction of positive and negative ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lafleur, T., E-mail: trevor.lafleur@lpp.polytechnique.fr; ONERA-The French Aerospace Lab, 91120 Palaiseau; Aanesland, A.

Using a combined analytical and simulation approach, we investigate positive and negative ion extraction between two electrodes from an ion-ion plasma source. With a square voltage waveform applied to the electrodes, we obtain approximate analytical solutions for the time-averaged extracted current densities, which are given simply by: J{sub p}{sup ac}=[α−fL√((M{sub p})/(q{sub p}V{sub 0}) )]J{sub p}{sup dc}, and J{sub n}{sup ac}=[(1−α)−fL√((M{sub n})/(q{sub n}V{sub 0}) )]J{sub n}{sup dc}, where J{sup ac} is the time-averaged current density, α is the square waveform duty cycle, f is the frequency, L is the electrode gap length, M is the ion mass, q is the ionmore » charge, V{sub 0} is the applied voltage amplitude, J{sup dc} is the dc extracted current density, and the subscripts p and n refer to positive and negative ions, respectively. In particular, if J{sup dc} is the dc space-charge limited current density, then these equations describe the square waveform generalization of the Child-Langmuir law.« less

Surge Protection in Low-Voltage AC Power Circuits: An Anthology

NASA Astrophysics Data System (ADS)

Martzloff, F. D.

2002-10-01

The papers included in this part of the Anthology provide basic information on the propagation of surges in low-voltage AC power circuits. The subject was approached by a combination of experiments and theoretical considerations. One important distinction is made between voltage surges and current surges. Historically, voltage surges were the initial concern. After the introduction and widespread use of current-diverting surge-protective devices at the point-of-use, the propagation of current surges became a significant factor. The papers included in this part reflect this dual dichotomy of voltage versus current and impedance mismatch effects versus simple circuit theory.

Ion-selective detection by plasticized poly(vinyl chloride) membrane in glass nanopipette with alternating voltage modulation.

PubMed

Deng, Xiao Long; Takami, Tomohide; Son, Jong Wan; Kang, Eun Ji; Kawai, Tomoji; Park, Bae Ho

2013-08-01

An alternating current (AC) voltage modulation was applied to ion-selective observations with plasticized poly(vinyl chloride) membranes in glass nanopipettes. The liquid confronting the membranes in the nanopipettes, the conditioning process, and AC voltage modulation play important roles in the ion-selective detection. In the AC detection system developed by us, where distilled water was used as the liquid within the nanopipettes, potassium ions were selectively detected in the sample solution of sodium and potassium ions because sodium ions were captured at the membrane containing bis(12-crown-4) ionophores, before the saturation of the ionophores. The membrane lost the selectivity after the saturation. On using sodium chloride as the liquid within the nanopipette, the membrane selectively detected potassium and sodium ions before and after the saturation of ionophores, respectively. The ion-selective detection of our system can be explained by the ion extraction-diffusion-dissolution mechanism through the bis(12-crown-4) ionophores with AC voltage modulation.

Influence of direct and alternating current electric fields on efficiency promotion and leaching risk alleviation of chelator assisted phytoremediation.

PubMed

Luo, Jie; Cai, Limei; Qi, Shihua; Wu, Jian; Sophie Gu, Xiaowen

2018-03-01

Direct and alternating current electric fields with various voltages were used to improve the decontamination efficiency of chelator assisted phytoremediation for multi-metal polluted soil. The alleviation effect of electric field on leaching risk caused by chelator application during phytoremediation process was also evaluated. Biomass yield, pollutant uptake and metal leaching retardation under alternating current (AC) and direct current (DC) electric fields were compared. The biomass yield of Eucalyptus globulus under AC fields with various voltages (2, 4 and 10 V) were 3.91, 4.16 and 3.67kg, respectively, significantly higher than the chelator treatment without electric field (2.71kg). Besides growth stimulation, AC fields increased the metal concentrations of plant tissues especially in aerial parts manifested by the raised translocation factor of different metals. Direct current electric fields with low and moderate voltages increased the biomass production of the species to 3.45 and 3.12kg, respectively, while high voltage on the contrary suppressed the growth of the plants (2.66kg). Under DC fields, metal concentrations elevated obviously with increasing voltages and the metal translocation factors were similar under all voltages. Metal extraction per plant achieved the maximum value under moderate voltage due to the greatest biomass production. DC field with high voltage (10V) decreased the volume of leachate from the chelator treatment without electric field from 1224 to 56mL, while the leachate gathered from AC field treatments raised from 512 to 670mL. DC field can retard the downward movement of metals caused by chelator application more effectively relative to AC field due to the constant water flow and electroosmosis direction. Alternating current field had more promotive effect on chelator assisted phytoremediation efficiency than DC field illustrated by more metal accumulation in the species. However, with the consideration of leaching risk, DC field with moderate voltage was the optimal supplementary technique for phytoremediation. Copyright © 2017 Elsevier Inc. All rights reserved.

Multimode power processor

DOEpatents

O'Sullivan, G.A.; O'Sullivan, J.A.

1999-07-27

In one embodiment, a power processor which operates in three modes: an inverter mode wherein power is delivered from a battery to an AC power grid or load; a battery charger mode wherein the battery is charged by a generator; and a parallel mode wherein the generator supplies power to the AC power grid or load in parallel with the battery. In the parallel mode, the system adapts to arbitrary non-linear loads. The power processor may operate on a per-phase basis wherein the load may be synthetically transferred from one phase to another by way of a bumpless transfer which causes no interruption of power to the load when transferring energy sources. Voltage transients and frequency transients delivered to the load when switching between the generator and battery sources are minimized, thereby providing an uninterruptible power supply. The power processor may be used as part of a hybrid electrical power source system which may contain, in one embodiment, a photovoltaic array, diesel engine, and battery power sources. 31 figs.

Multimode power processor

DOEpatents

O'Sullivan, George A.; O'Sullivan, Joseph A.

1999-01-01

In one embodiment, a power processor which operates in three modes: an inverter mode wherein power is delivered from a battery to an AC power grid or load; a battery charger mode wherein the battery is charged by a generator; and a parallel mode wherein the generator supplies power to the AC power grid or load in parallel with the battery. In the parallel mode, the system adapts to arbitrary non-linear loads. The power processor may operate on a per-phase basis wherein the load may be synthetically transferred from one phase to another by way of a bumpless transfer which causes no interruption of power to the load when transferring energy sources. Voltage transients and frequency transients delivered to the load when switching between the generator and battery sources are minimized, thereby providing an uninterruptible power supply. The power processor may be used as part of a hybrid electrical power source system which may contain, in one embodiment, a photovoltaic array, diesel engine, and battery power sources.

The ac power line protection for an IEEE 587 Class B environment

NASA Technical Reports Server (NTRS)

Roehr, W. D.; Clark, O. M.

1984-01-01

The 587B series of protectors are unique, low clamping voltage transient suppressors to protect ac-powered equipment from the 6000V peak open-circuit voltage and 3000A short circuit current as defined in IEEE standard 587 for Category B transients. The devices, which incorporate multiple-stage solid-state protector components, were specifically designed to operate under multiple exposures to maximum threat levels in this severe environment. The output voltage peaks are limited to 350V under maximum threat conditions for a 120V ac power line, thus providing adequate protection to vulnerable electronic equipment. The principle of operation and test performance data is discussed.

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

NASA Astrophysics Data System (ADS)

Qian, WANG; Feng, LIU; Chuanrun, MIAO; Bing, YAN; Zhi, FANG

2018-03-01

A coaxial dielectric barrier discharge (DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond (ns) pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 °C and 64.3 °C after 900 s operation, respectively. The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs, reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.

Analysis of partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique

NASA Astrophysics Data System (ADS)

Sarathi, R.; Giridhar, A. V.; Sethupathi, K.

2010-01-01

Liquid nitrogen (LN 2) is used as an insulant as well as coolant in high temperature superconducting power equipments. Particle contamination in liquid nitrogen is one of the major cause for formation of partial discharges during operation. An attempt has been made in the present study to understand the feasibility of using Ultra High Frequency (UHF) sensors for identification of partial discharge (PD) formed due to particle movement in liquid nitrogen under AC voltages. It is observed that the partial discharge formed in LN 2 radiates UHF signal. The results of the study indicate that the conventional partial discharge measurement and UHF peak amplitude measurement have direct correlation. The Phase Resolved Partial Discharge (PRPD) analysis indicates that the partial discharge formed due to particle movement occurs in the entire phase windows of the AC voltage. The PD magnitude increases with increase in applied voltage. The frequency content of UHF signal generated due to particle movement in liquid nitrogen under AC voltages lies in the range of 0.5-1.5 GHz. The UHF sensor output signal analyzed using spectrum analyzer by operating it in zero-span mode, indicates that burst type PD occurs due to particle movement.

An AC modulated near infrared gain calibration system for a "Violin-Mode" transimpedance amplifier, intended for advanced LIGO suspensions.

PubMed

Lockerbie, N A; Tokmakov, K V

2016-07-01

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a "tall-thin" rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse "Violin-Mode" vibrations of such a fibre, via the oscillatory movement of the shadow cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor's DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor's more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz-300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m(-1) was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m(-1), at that frequency.

Power Quality Control and Design of Power Converter for Variable-Speed Wind Energy Conversion System with Permanent-Magnet Synchronous Generator

PubMed Central

Oğuz, Yüksel; Güney, İrfan; Çalık, Hüseyin

2013-01-01

The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS) operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%. PMID:24453905

Power quality control and design of power converter for variable-speed wind energy conversion system with permanent-magnet synchronous generator.

PubMed

Oğuz, Yüksel; Güney, İrfan; Çalık, Hüseyin

2013-01-01

The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS) operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%.

An Improved Targeted cAMP Sensor to Study the Regulation of Adenylyl Cyclase 8 by Ca2+ Entry through Voltage-Gated Channels

PubMed Central

Everett, Katy L.; Cooper, Dermot M. F.

2013-01-01

Here we describe an improved sensor with reduced pH sensitivity tethered to adenylyl cyclase (AC) 8. The sensor was used to study cAMP dynamics in the AC8 microdomain of MIN6 cells, a pancreatic β-cell line. In these cells, AC8 was activated by Ca2+ entry through L-type voltage-gated channels following depolarisation. This activation could be reconstituted in HEK293 cells co-expressing AC8 and either the α1C or α1D subunit of L-type voltage-gated Ca2+ channels. The development of this improved sensor opens the door to the study of cAMP microdomains in excitable cells that have previously been challenging due to the sensitivity of fluorescent proteins to pH changes. PMID:24086669

Transmission line design for the lunar environment

NASA Technical Reports Server (NTRS)

Gaustad, Krista L.; Gordon, Lloyd B.

1990-01-01

How the mass, operating temperature, and efficiency of a transmission line operating on the moon are affected by its operating parameters, the lunar environment, and the choice of materials is examined. The key transmission line parameters which have an effect on mass, operating temperature, and efficiency are voltage, power loss, and waveform. The choice of waveform for transmission will be influenced by the waveform of the source and load, and therefore an analysis of both DC and AC transmission is necessary for a complete understanding of lunar power transmission. The data presented are for the DC case only; however, the discussion of the environmental effects and of material selection is pertinent to both AC and DC transmission. The operating voltage is shown to be a key parameter in transmission line design. The role efficiency plays in transmission line design is also examined. The analyses include above- and below-the-surface operation for both a vacuum-insulated, two-wire, transmission line, and a solid-dielectric-insulated, coaxial, transmission line.

Breakdown characteristics of atmospheric dielectric barrier discharge in gas flow condition

NASA Astrophysics Data System (ADS)

Fan, Zhihui; Yan, Huijie; Wang, Yuying; Liu, Yidi; Guo, Hongfei; Ren, Chunsheng

2018-05-01

Experimental investigations of the breakdown characteristics of plate-to-plate dielectric barrier discharge excited by an AC source at different gas flow conditions are carried out. The ignition voltage for the appearance of the very first discharge filament and the breakdown voltage in each discharge half cycle in continuous operation are examined. As revealed by the results of the indoor air experiment, the ignition voltage manifests a monotonous increase with the increase in the gas flow rate, while the breakdown voltage has a marked decline at the low gas flow rate and increases slightly as the gas flow rate is higher than 10 m/s. As regards the obvious decreases in the ignition voltage and breakdown voltage, the decrease in the humidity with the increase in the gas flow rate plays a dominant role. As regards the increase in breakdown voltage, the memory effect from the preceding discharge is considered. The losses of metastable particles, together with particles having high translational energy in the gas flow, are considered to be the most critical factors.

A 13.56 MHz CMOS Active Rectifier With Switched-Offset and Compensated Biasing for Biomedical Wireless Power Transfer Systems.

PubMed

Yan Lu; Wing-Hung Ki

2014-06-01

A full-wave active rectifier switching at 13.56 MHz with compensated bias current for a wide input range for wirelessly powered high-current biomedical implants is presented. The four diodes of a conventional passive rectifier are replaced by two cross-coupled PMOS transistors and two comparator- controlled NMOS switches to eliminate diode voltage drops such that high voltage conversion ratio and power conversion efficiency could be achieved even at low AC input amplitude |VAC|. The comparators are implemented with switched-offset biasing to compensate for the delays of active diodes and to eliminate multiple pulsing and reverse current. The proposed rectifier uses a modified CMOS peaking current source with bias current that is quasi-inversely proportional to the supply voltage to better control the reverse current over a wide AC input range (1.5 to 4 V). The rectifier was fabricated in a standard 0.35 μm CMOS N-well process with active area of 0.0651 mm(2). For the proposed rectifier measured at |VAC| = 3.0 V, the voltage conversion ratios are 0.89 and 0.93 for RL=500 Ω and 5 kΩ, respectively, and the measured power conversion efficiencies are 82.2% to 90.1% with |VAC| ranges from 1.5 to 4 V for RL=500 Ω.

Piezotube borehole seismic source

DOEpatents

Daley, Tom M; Solbau, Ray D; Majer, Ernest L

2014-05-06

A piezoelectric borehole source capable of permanent or semipermanent insertion into a well for uninterrupted well operations is described. The source itself comprises a series of piezoelectric rings mounted to an insulative mandrel internally sized to fit over a section of well tubing, the rings encased in a protective housing and electrically connected to a power source. Providing an AC voltage to the rings will cause expansion and contraction sufficient to create a sonic pulse. The piezoelectric borehole source fits into a standard well, and allows for uninterrupted pass-through of production tubing, and other tubing and electrical cables. Testing using the source may be done at any time, even concurrent with well operations, during standard production.

Linking results of key and supplementary comparisons of AC/DC voltage transfer references

NASA Astrophysics Data System (ADS)

Velychko, Oleh

2018-04-01

A regional key comparison (KC) COOMET.EM-K6.a and a supplementary comparison (SC) COOMET.EM-S1 of AC/DC voltage transfer references were conducted between participating laboratories from the Eurasian region. Measurements were made over the period 2004-2014. The results showed good agreement between all but one of the participating laboratories. The proposed procedure of linking results of key and SCs of regional metrology organization of AC/DC voltage transfer references is presented. Linking results is realized for COOMET.EM-K6.a and CCEM-K6.a KCs, and for COOMET.EM-K6.a KC and COOMET.EM-S1 SC.

An Improved Power Quality Based Sheppard-Taylor Converter Fed BLDC Motor Drive

NASA Astrophysics Data System (ADS)

Singh, Bhim; Bist, Vashist

2015-12-01

This paper deals with the design and analysis of a power factor correction based Sheppard-Taylor converter fed brushless dc motor (BLDCM) drive. The speed of the BLDCM is controlled by adjusting the dc link voltage of the voltage source inverter (VSI) feeding BLDCM. Moreover, a low frequency switching of the VSI is used for electronically commutating the BLDCM for reduced switching losses. The Sheppard-Taylor converter is designed to operate in continuous conduction mode to achieve an improved power quality at the ac mains for a wide range of speed control and supply voltage variation. The BLDCM drive is designed and its performance is simulated in a MATLAB/Simulink environment to achieve the power quality indices within the limits of the international power quality standard IEC-61000-3-2.

Power converter

NASA Technical Reports Server (NTRS)

Black, J. M. (Inventor)

1981-01-01

A dc-to-dc converter employs four transistor switches in a bridge to chop dc power from a source, and a voltage multiplying diode rectifying ladder network to rectify and filter the chopped dc power for delivery to a load. The bridge switches are cross coupled in order for diagonally opposite pairs to turn on and off together using RC networks for the cross coupling to achieve the mode of operation of a free running multivibrator, and the diode rectifying ladder is configured to operate in a push-pull mode driven from opposite sides of the multivibrator outputs of the ridge switches. The four transistor switches provide a square-wave output voltage which as a peak-to-peak amplitude that is twice the input dc voltage, and is thus useful as a dc-to-ac inverter.

Synchronization algorithm for three-phase voltages of an inverter and a grid

NASA Astrophysics Data System (ADS)

Nos, O. V.

2017-07-01

This paper presents the results of designing a joint phase-locked loop for adjusting the phase shifts (speed) and Euclidean norm of three-phase voltages of an inverter to the same grid parameters. The design can be used, in particular, to match the potentials of two parallel-connected power sources for the fundamental harmonic at the moments of switching the stator windings of an induction AC motor from a converter to a centralized power-supply system and back. Technical implementation of the developed synchronization algorithm will significantly reduce the inductance of the current-balancing reactor and exclude emergency operation modes in the electric motor power circuit.

Low Voltage Electrowetting on Ferroelectric PVDF-HFP Insulator with Highly Tunable Contact Angle Range.

PubMed

Sawane, Yogesh B; Ogale, Satishchandra B; Banpurkar, Arun G

2016-09-14

We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles. But the contact angle modulation for DC voltage shows a hysteresis because of the field-induced residual polarization in the ferroelectric layer. Finally, we show that a thin bilayer exhibits contact angle modulation of Δθ (U) ≈ 60° at merely 15 V amplitude of AC voltage indicating a potential dielectric for practical low voltage electrowetting applications. A proof of concept confirms electrowetting based rapid mixing of a fluorescent dye in aqueous glycerol solution for 15 V AC signal.

A grid-connected single-phase photovoltaic micro inverter

NASA Astrophysics Data System (ADS)

Wen, X. Y.; Lin, P. J.; Chen, Z. C.; Wu, L. J.; Cheng, S. Y.

2017-11-01

In this paper, the topology of a single-phase grid-connected photovoltaic (PV) micro-inverter is proposed. The PV micro-inverter consists of DC-DC stage with high voltage gain boost and DC-AC conversion stage. In the first stage, we apply the active clamp circuit and two voltage multipliers to achieve soft switching technology and high voltage gain. In addition, the flower pollination algorithm (FPA) is employed for the maximum power point tracking (MPPT) in the PV module in this stage. The second stage cascades a H-bridge inverter and LCL filter. To feed high quality sinusoidal power into the grid, the software phase lock, outer voltage loop and inner current loop control method are adopted as the control strategy. The performance of the proposed topology is tested by Matlab/Simulink. A PV module with maximum power 300W and maximum power point voltage 40V is applied as the input source. The simulation results indicate that the proposed topology and the control strategy are feasible.

Power-Quality Improvement in PFC Bridgeless SEPIC-Fed BLDC Motor Drive

NASA Astrophysics Data System (ADS)

Singh, Bhim; Bist, Vashist

2013-06-01

This article presents a design of a power factor correction (PFC)-based brushless DC (BLDC) motor drive. The speed control of BLDC motor is achieved by controlling the DC link voltage of the voltage source inverter (VSI) feeding BLDC motor using a single voltage sensor. A front-end bridgeless single-ended primary inductance converter (SEPIC) is used for DC link voltage control and PFC operation. A bridgeless SEPIC is designed to operate in discontinuous inductor current mode (DICM) thus utilizing a simple control scheme of voltage follower. An electronic commutation of BLDC motor is used for VSI to operate in a low-frequency operation for reduced switching losses in the VSI. Moreover, a bridgeless topology offers less conduction losses due to absence of diode bridge rectifier for further increasing the efficiency. The proposed BLDC motor drive is designed to operate over a wide range of speed control with an improved power-quality at the AC mains under the recommended international power-quality standards such as IEC 61000-3-2.

Module Twelve: Series AC Resistive-Reactive Circuits; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

The module covers series circuits which contain both resistive and reactive components and methods of solving these circuits for current, voltage, impedance, and phase angle. The module is divided into six lessons: voltage and impedance in AC (alternating current) series circuits, vector computations, rectangular and polar notation, variational…

Power factor control system for AC induction motors

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1977-01-01

A power factor control system for use with ac induction motors was designed which samples lines voltage and current through the motor and decreases power input to the motor proportional to the detected phase displacement between current and voltage. This system provides, less power to the motor, as it is less loaded.

A new venous infusion pathway monitoring system.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sata, Koji; Hamada, Shingo; Caldwell, W Morton

2007-01-01

A new infusion catheter pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer has been developed for hospital and home use. The sensor consists of coaxial three-layer conductive tapes wrapped around the polyvinyl chloride infusion tube. The inner tape is the main electrode, which records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. The outside tape layer is a reference electrode to monitor the AC voltage around the main electrode. The center tape layer is connected to system ground and functions as a shield. The microcomputer calculates the ratio of the induced AC voltages recorded by the main and reference electrodes and if the ratio indicates a detached infusion, alerts the nursing station, via the nurse call system or low transmitting power mobile phone.

Influence of barrier on partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique

NASA Astrophysics Data System (ADS)

Sarathi, R.; Giridhar, A. V.; Sethupathi, K.

2011-02-01

The UHF signals are generated due to PD formed by particle movement in liquid nitrogen under AC voltages. The levitation voltage of a particle in liquid nitrogen measured through UHF technique and by conventional PD measurement technique is the same, confirming the sensitivity of UHF technique for identification of PD activity. The frequency content of UHF signal generated due to particle movement in liquid nitrogen, under AC voltages, lies in the range 0.5-1.5 GHz. The characteristics of UHF signal generated due to particle movement between the barrier and high voltage/ground electrode is much similar to the signal generated by particle movement in clean electrode gap. Pseudo resonance phenomena can occur in liquid nitrogen due to particle movement. It is also observed that the partial discharge magnitude, in general, be high when the particle moves between the barrier and high voltage electrode when compared to the barrier and the ground electrode. Percentage of clay in epoxy nanocomposites has not altered the levitation voltage of the particle in the electrode gap. Zero span analysis clearly indicates that pseudo resonance occurs when particle moves (in a short gap) between the barrier and high voltage/ground electrode.

Experimental investigations of an AC pulse heating method for vehicular high power lithium-ion batteries at subzero temperatures

NASA Astrophysics Data System (ADS)

Zhu, Jiangong; Sun, Zechang; Wei, Xuezhe; Dai, Haifeng; Gu, Weijun

2017-11-01

Effect of the AC (alternating current) pulse heating method on battery SoH (state of health) for large laminated power lithium-ion batteries at low temperature is investigated experimentally. Firstly, excitation current frequencies, amplitudes, and voltage limitations on cell temperature evolution are studied. High current amplitudes facilitate the heat accumulation and temperature rise. Low frequency region serves as a good innovation to heat the battery because of the large impedance. Wide voltage limitations also enjoy better temperature evolution owing to the less current modulation, but the temperature difference originated from various voltage limitations attenuates due to the decrement of impedance resulting from the temperature rise. Experiments with the thermocouple-embedded cell manifest good temperature homogeneity between the battery surface and interior during the AC heating process. Secondly, the cell capacity, Direct Current resistance and Electrochemical Impedance Spectroscopy are all calibrated to assess the battery SoH after the hundreds of AC pulse heating cycles. Also, all cells are disassembled to investigate the battery internal morphology with the employment of Scanning Electron Microscope and Energy-Dispersive x-ray Spectroscopy techniques. The results indicate that the AC heating method does not aggravate the cell degradation even in the low frequency range (0.5 Hz) under the normal voltage protection limitation.

Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

NASA Astrophysics Data System (ADS)

Demirezen, S.; Kaya, A.; Yerişkin, S. A.; Balbaşı, M.; Uslu, İ.

In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε‧, ε‧, tanδ, electric modulus (M‧ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε‧, ε‧, tanδ, M‧, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε‧, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε‧ and ε″ values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of ε‧ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M‧ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M‧ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε‧, ε″, tanδ, M‧, M″ and ac electric conductivity (σac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

Direct current uninterruptible power supply method and system

DOEpatents

Sinha, Gautam

2003-12-02

A method and system are described for providing a direct current (DC) uninterruptible power supply with the method including, for example: continuously supplying fuel to a turbine; converting mechanical power from the turbine into alternating current (AC) electrical power; converting the AC electrical power to DC power within a predetermined voltage level range; supplying the DC power to a load; and maintaining a DC load voltage within the predetermined voltage level range by adjusting the amount of fuel supplied to the turbine.

Comparative study of superconducting fault current limiter both for LCC-HVDC and VSC-HVDC systems

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Lim, Sung-Woo; Shin, Woo-ju; Seo, In-Jin; Lee, Bang-Wook

2015-11-01

High Voltage Direct Current (HVDC) system has been evaluated as the optimum solution for the renewable energy transmission and long-distance power grid connections. In spite of the various advantages of HVDC system, it still has been regarded as an unreliable system compared to AC system due to its vulnerable characteristics on the power system fault. Furthermore, unlike AC system, optimum protection and switching device has not been fully developed yet. Therefore, in order to enhance the reliability of the HVDC systems mitigation of power system fault and reliable fault current limiting and switching devices should be developed. In this paper, in order to mitigate HVDC fault, both for Line Commutated Converter HVDC (LCC-HVDC) and Voltage Source Converter HVDC (VSC-HVDC) system, an application of resistive superconducting fault current limiter which has been known as optimum solution to cope with the power system fault was considered. Firstly, simulation models for two types of LCC-HVDC and VSC-HVDC system which has point to point connection model were developed. From the designed model, fault current characteristics of faulty condition were analyzed. Second, application of SFCL on each types of HVDC system and comparative study of modified fault current characteristics were analyzed. Consequently, it was deduced that an application of AC-SFCL on LCC-HVDC system with point to point connection was desirable solution to mitigate the fault current stresses and to prevent commutation failure in HVDC electric power system interconnected with AC grid.

The Design of Operational Amplifier for Low Voltage and Low Current Sound Energy Harvesting System

NASA Astrophysics Data System (ADS)

Fang, Liew Hui; Rahim, Rosemizi Bin Abd; Isa, Muzamir; Idris Syed Hassan, Syed; Ismail, Baharuddin Bin

2018-03-01

The objective of this paper is to design a combination of an operational amplifier (op-amp) with a rectifier used in an alternate current (ac) to direct current (dc) power conversion. The op-amp was designed to specifically work at low voltage and low current for a sound energy harvesting system. The goal of the op-amp design with adjustable gain was to control output voltage based on the objectives of the experiment conducted. The op-amp was designed for minimum power dissipation performance, with the means of increasing the output current when receiving a large amount of load. The harvesting circuits which designed further improved the power output efficiency by shortening the fully charged time needed by a supercapacitor bank. It can fulfil the long-time power demands for low power device. Typically, a small amount of energy sources were converted to electricity and stored in the supercapacitor bank, which was built by 10 pieces of capacitors with 0.22 F each, arranged in parallel connection. The highest capacitance was chosen based on the characteristic that have the longest discharging time to support the applications of a supercapacitor bank. Testing results show that the op-amp can boost the low input ac voltage (∼3.89 V) to high output dc voltage (5.0 V) with output current of 30 mA and stored the electrical energy in a big supercapacitor bank having a total of 2.2 F, effectively. The measured results agree well with the calculated results.

Changes in behavioral responses of Lygus lineolaris (Hemiptera: Miridae) from various applied signal voltages during EPG recordings

USDA-ARS?s Scientific Manuscript database

A 3rd-generation AC-DC electrical penetration graph (EPG) monitor was used to study feeding behaviors of pre-reproductive adult Lygus lineolaris (Hemiptera: Miridae) on pinhead (<3mm) cotton squares, applying different signal voltages at several input impedances. The AC-DC monitor allows a user to s...

A dry-cooled AC quantum voltmeter

NASA Astrophysics Data System (ADS)

Schubert, M.; Starkloff, M.; Peiselt, K.; Anders, S.; Knipper, R.; Lee, J.; Behr, R.; Palafox, L.; Böck, A. C.; Schaidhammer, L.; Fleischmann, P. M.; Meyer, H.-G.

2016-10-01

The paper describes a dry-cooled AC quantum voltmeter system operated up to kilohertz frequencies and 7 V rms. A 10 V programmable Josephson voltage standard (PJVS) array was installed on a pulse tube cooler (PTC) driven with a 4 kW air-cooled compressor. The operating margins at 70 GHz frequencies were investigated in detail and found to exceed 1 mA Shapiro step width. A key factor for the successful chip operation was the low on-chip power consumption of 65 mW in total. A thermal interface between PJVS chip and PTC cold stage was used to avoid a significant chip overheating. By installing the cryocooled PJVS array into an AC quantum voltmeter setup, several calibration measurements of dc standards and calibrator ac voltages up to 2 kHz frequencies were carried out to demonstrate the full functionality. The results are discussed and compared to systems with standard liquid helium cooling. For dc voltages, a direct comparison measurement between the dry-cooled AC quantum voltmeter and a liquid-helium based 10 V PJVS shows an agreement better than 1 part in 1010.

Robust backstepping control of an interlink converter in a hybrid AC/DC microgrid based on feedback linearisation method

NASA Astrophysics Data System (ADS)

Dehkordi, N. Mahdian; Sadati, N.; Hamzeh, M.

2017-09-01

This paper presents a robust dc-link voltage as well as a current control strategy for a bidirectional interlink converter (BIC) in a hybrid ac/dc microgrid. To enhance the dc-bus voltage control, conventional methods strive to measure and feedforward the load or source power in the dc-bus control scheme. However, the conventional feedforward-based approaches require remote measurement with communications. Moreover, conventional methods suffer from stability and performance issues, mainly due to the use of the small-signal-based control design method. To overcome these issues, in this paper, the power from DG units of the dc subgrid imposed on the BIC is considered an unmeasurable disturbance signal. In the proposed method, in contrast to existing methods, using the nonlinear model of BIC, a robust controller that does not need the remote measurement with communications effectively rejects the impact of the disturbance signal imposed on the BIC's dc-link voltage. To avoid communication links, the robust controller has a plug-and-play feature that makes it possible to add a DG/load to or remove it from the dc subgrid without distorting the hybrid microgrid stability. Finally, Monte Carlo simulations are conducted to confirm the effectiveness of the proposed control strategy in MATLAB/SimPowerSystems software environment.

Control Structures for VSC-based FACTS Devices under Normal and Faulted AC-systems

NASA Astrophysics Data System (ADS)

Babaei, Saman

This thesis is concerned with improving the Flexible AC Transmission Systems (FACTS) devices performance under the normal and fault AC-system conditions by proposing new control structures and also converter topologies. The combination of the increasing electricity demand and restrictions in expanding the power system infrastructures has urged the utility owners to deploy the utility-scaled power electronics in the power system. Basically, FACTS is referred to the application of the power electronics in the power systems. Voltage Source Converter (VSC) is the preferred building block of the FACTS devices and many other utility-scale power electronics applications. Despite of advances in the semiconductor technology and ultra-fast microprocessor based controllers, there are still many issues to address and room to improve[25]. An attempt is made in this thesis to address these important issues of the VSC-based FACTS devices and provide solutions to improve them.

EV drivetrain inverter with V/HZ optimization

DOEpatents

Gritter, David J.; O'Neil, Walter K.

1986-01-01

An inverter (34) which provides power to an A.C. machine (28) is controlled by a circuit (36) employing PWM control strategy whereby A.C. power is supplied to the machine at a preselectable frequency and preselectable voltage. This is accomplished by the technique of waveform notching in which the shapes of the notches are varied to determine the average energy content of the overall waveform. Through this arrangement, the operational efficiency of the A.C. machine is optimized. The control circuit includes a micro-computer which calculates optimized machine control data signals from various parametric inputs and during steady state load conditions, seeks a best V/HZ ratio to minimize battery current drawn (system losses) from a D.C. power source (32). In the preferred embodiment, the present invention is incorporated within an electric vehicle (10) employing a 144 VDC battery pack and a three-phase induction motor (18).

Hybrid AC-High Voltage DC Grid Stability and Controls

NASA Astrophysics Data System (ADS)

Yu, Jicheng

The growth of energy demands in recent years has been increasing faster than the expansion of transmission facility construction. This tendency cooperating with the continuous investing on the renewable energy resources drives the research, development, and construction of HVDC projects to create a more reliable, affordable, and environmentally friendly power grid. Constructing the hybrid AC-HVDC grid is a significant move in the development of the HVDC techniques; the form of dc system is evolving from the point-to-point stand-alone dc links to the embedded HVDC system and the multi-terminal HVDC (MTDC) system. The MTDC is a solution for the renewable energy interconnections, and the MTDC grids can improve the power system reliability, flexibility in economic dispatches, and converter/cable utilizing efficiencies. The dissertation reviews the HVDC technologies, discusses the stability issues regarding the ac and HVDC connections, proposes a novel power oscillation control strategy to improve system stability, and develops a nonlinear voltage droop control strategy for the MTDC grid. To verify the effectiveness the proposed power oscillation control strategy, a long distance paralleled AC-HVDC transmission test system is employed. Based on the PSCAD/EMTDC platform simulation results, the proposed power oscillation control strategy can improve the system dynamic performance and attenuate the power oscillations effectively. To validate the nonlinear voltage droop control strategy, three droop controls schemes are designed according to the proposed nonlinear voltage droop control design procedures. These control schemes are tested in a hybrid AC-MTDC system. The hybrid AC-MTDC system, which is first proposed in this dissertation, consists of two ac grids, two wind farms and a five-terminal HVDC grid connecting them. Simulation studies are performed in the PSCAD/EMTDC platform. According to the simulation results, all the three design schemes have their unique salient features.

Frequency Dependence of Low-Voltage Electrowetting Investigated by Impedance Spectroscopy.

PubMed

Li, Ying-Jia; Cahill, Brian P

2017-11-14

An electrowetting-on-dielectric (EWOD) electrode was developed that facilitates the use of low alternating voltages (≤5 V AC ). This allows online investigation of the frequency dependence of electrowetting by means of impedance spectroscopy. The EWOD electrode is based on a dielectric bilayer consisting of an anodic tantalum pentoxide (Ta 2 O 5 ) thin film (d = 59.35 nm) with a high relative permittivity (ε d = 26.3) and a self-assembled hydrophobic silane monolayer. The frequency dependence of electrowetting was studied using an aqueous μL-sized sessile droplet on the planar EWOD electrode in oil. Experiments using electrochemical impedance spectroscopy and optical imaging indicate the frequency dependence of all three variables in the Young-Lippmann equation: the voltage drop across the dielectric layers, capacitance per unit area, and contact angle under voltage. The electrowetting behavior induced by AC voltages is shown to be well described by the Young-Lippmann equation for AC applications below a frequency threshold. Moreover, the dielectric layers act as a capacitor and the stored electrostatic potential energy is revealed to only partially contribute to the electrowetting.

Shipboard Aggregate Power Monitoring

DTIC Science & Technology

2009-06-01

low pressure air serves to operate various valves and provide pneumatic power for certain plant equipment. The compressor is an Ingersoll-Rand NAXI...List of Figures Figure 1-1: Raw AC voltage and current measurements for recorded during a motor start-up. (1...filters, valves, etc.) of a given system. Figure 1-1: Raw AC voltage and current measurements recorded during a motor start-up. (1) Figure

Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

DOEpatents

Gallegos-Lopez, Gabriel [Torrance, CA; Nagashima, James M [Cerritos, CA; Perisic, Milun [Torrance, CA; Hiti, Silva [Redondo Beach, CA

2012-06-05

A system is provided for controlling two alternating current (AC) machines via a five-phase PWM inverter module. The system comprises a first control loop, a second control loop, and a current command adjustment module. The current command adjustment module operates in conjunction with the first control loop and the second control loop to continuously adjust current command signals that control the first AC machine and the second AC machine such that they share the input voltage available to them without compromising the target mechanical output power of either machine. This way, even when the phase voltage available to either one of the machines decreases, that machine outputs its target mechanical output power.

An AC modulated near infrared gain calibration system for a “Violin-Mode” transimpedance amplifier, intended for advanced LIGO suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lockerbie, N. A.; Tokmakov, K. V.

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a “tall-thin” rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse “Violin-Mode” vibrations of such a fibre, via the oscillatory movement of the shadowmore » cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor’s DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor’s more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz–300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m{sup −1} was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m{sup −1}, at that frequency.« less

A Comparison of Alternating Current and Direct Current Electrospray Ionization for Mass Spectrometry

PubMed Central

Sarver, Scott A.; Gartner, Carlos A.; Chetwani, Nishant; Go, David B.; Dovichi, Norman J.

2014-01-01

A series of studies comparing the performance of alternating current electrospray ionization (AC ESI) mass spectrometry (MS) and direct current electrospray ionization (DC ESI) MS has been conducted, exploring the absolute signal intensity and signal-to-background ratios produced by both methods using caffeine and a model peptide as targets. Because the high-voltage AC signal was more susceptible to generating gas discharges, the operating voltage range of AC ESI was significantly smaller than that for DC ESI, such that the absolute signal intensities produced by DC ESI at peak voltages were 1 - 2 orders of magnitude greater than those for AC ESI. Using an electronegative nebulizing gas, sulfur hexafluoride (SF6), instead of nitrogen (N2) increased the operating range of AC ESI by ~50%, but did not appreciably improve signal intensities. While DC ESI generated far greater signal intensities, both ionization methods produced comparable signal-to-background noise, with AC ESI spectra appearing qualitatively cleaner. A quantitative calibration analysis was performed for two analytes, caffeine and the peptide MRFA. AC ESI utilizing SF6 outperforms all other techniques for the detection of MRFA, producing chromatographic limits of detection nearly one order of magnitude lower than that of DC ESI utilizing N2, and one half that of DC ESI utilizing SF6. However, DC ESI outperforms AC ESI for the analysis of caffeine, indicating improvements in spectral quality may benefit certain compounds, or classes of compounds, on an individual basis. PMID:24464359

Effect of surfactants on dielectric strength of crude oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yunusov, A.A.

1995-09-01

In all the methods used for crude oil demulsification, including electrodemulsification, surfactants are used to aid the demulsification. Therefore, the present work has been aimed at studying the character and degree of influence of surfactants on the dielectric strength of crude oil. Our experiments were performed with a standard discharger at an AC frequency of 50 Hz. The high-voltage source was a universal breakdown unit of the UPU-1 type.

Mitigation of commutation failures in LCC-HVDC systems based on superconducting fault current limiters

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Lee, Ho-Yun; Lim, Sung-Woo; Lee, Bang-Wook

2016-11-01

Commutation failure in line commutated converter based HVDC systems cause severe damages on the entire power grid system. For LCC-HVDC, thyristor valves are turned on by a firing signal but turn off control is governed by the external applied AC voltage from surrounding network. When the fault occurs in AC system, turn-off control of thyristor valves is unavailable due to the voltage collapse of point of common coupling (PCC), which causes the commutation failure in LCC-HVDC link. Due to the commutation failure, the power transfer interruption, dc voltage drop and severe voltage fluctuation in the AC system could be occurred. In a severe situation, it might cause the protection system to block the valves. In this paper, as a solution to prevent the voltage collapse on PCC and to limit the fault current, the application study of resistive superconducting fault current limiter (SFCL) on LCC-HVDC grid system was performed with mathematical and simulation analyses. The simulation model was designed by Matlab/Simulink considering Haenam-Jeju HVDC power grid in Korea which includes conventional AC system and onshore wind farm and resistive SFCL model. From the result, it was observed that the application of SFCL on LCC-HVDC system is an effective solution to mitigate the commutation failure. And then the process to determine optimum quench resistance of SFCL which enables the recovery of commutation failure was deeply investigated.

The electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures

NASA Astrophysics Data System (ADS)

Karabulut, Abdulkerim; Türüt, Abdulmecit; Karataş, Şükrü

2018-04-01

In this work, temperature dependent electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures were investigated using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60-320 K by steps of 20 K at 1 MHz. The dielectric constant (ε‧), dielectric loss (ε″), dielectric loss tangent (tanδ) and ac electrical conductivities (σac) have been calculated as a function of temperature. These values of the ε‧, ε″, tanδ and σac have been found to be 2.272, 5.981, 2.631 and 3.32 × 10-6 (Ω-1cm-1) at 80 K, respectively, 1.779, 2.315, 1.301 and 1.28 × 10-6 (Ω-1cm-1), respectively at 320 K. These decrease of the dielectric parameters (ε‧, ε″, tanδ and σac) have been observed at high temperatures. The experimental results show that electrical and dielectric properties are strongly temperature and bias voltage dependent.

Simulation comparison of proportional integral derivative and fuzzy logic in controlling AC-DC buck boost converter

NASA Astrophysics Data System (ADS)

Faisal, A.; Hasan, S.; Suherman

2018-03-01

AC-DC converter is widely used in the commercial industry even for daily purposes. The AC-DC converter is used to convert AC voltage into DC. In order to obtain the desired output voltage, the converter usually has a controllable regulator. This paper discusses buck boost regulator with a power MOSFET as switching component which is adjusted based on the duty cycle of pulse width modulation (PWM). The main problems of the buck boost converter at start up are the high overshoot, the long peak time and rise time. This paper compares the effectiveness of two control techniques: proportional integral derivative (PID) and fuzzy logic control in controlling the buck boost converter through simulations. The results show that the PID is more sensitive to voltage change than fuzzy logic. However, PID generates higher overshoot, long peak time and rise time. On the other hand, fuzzy logic generates no overshoot and shorter rise time.

Power electronic supply system with the wind turbine dedicated for average power receivers

NASA Astrophysics Data System (ADS)

Widerski, Tomasz; Skrzypek, Adam

2018-05-01

This article presents the original project of the AC-DC-AC converter dedicated to low power wind turbines. Such a set can be a good solution for powering isolated objects that do not have access to the power grid, for example isolated houses, mountain lodges or forester's lodges, where they can replace expensive diesel engine generators. An additional source of energy in the form of a mini-wind farm is also a good alternative to yachts, marinas and tent sites, which are characterized by relatively low power consumption. This article presents a designed low power wind converter that is dedicated to these applications. The main design idea of the authors was to create a device that converts the very wide range input voltage directly to a stable 230VAC output voltage without the battery buffer. Authors focused on maximum safety of using and service. The converter contains the thermal protection, short-circuit protection and overvoltage protection. The components have been selected in such a way as to ensure that the device functions as efficiently as possible.

Effect of an alternating current electric field on Co(OH)2 periodic precipitation

NASA Astrophysics Data System (ADS)

Karam, Tony; Sultan, Rabih

2013-02-01

The present paper studies the effect of an alternating current (AC) electric field on Co(OH)2 Liesegang patterns. In the presence of an AC electric field, the band spacing increases with spacing number, but reaches a plateau at large spacing (or band) numbers. The band spacing increases with applied AC voltage, but to a much lesser extent than the effect of a DC electric field under the same applied voltage [see R. Sultan, R. Halabieh, Chem. Phys. Lett. 332 (2000) 331][1]. At low enough applied voltage, the band spacing increases with frequency. At higher voltages, the band spacing becomes independent of the field frequency. The effect of concentration of the inner electrolyte (Co2+), exactly opposes that observed under DC electric field; i.e., the band spacing decreases with increasing concentration. The dynamics were shown to be governed by a competitive scenario between the diffusion gradient and the alternating current electric field factor.

Spin pumping and inverse spin Hall voltages from dynamical antiferromagnets

NASA Astrophysics Data System (ADS)

Johansen, Øyvind; Brataas, Arne

2017-06-01

Dynamical antiferromagnets can pump spins into adjacent conductors. The high antiferromagnetic resonance frequencies represent a challenge for experimental detection, but magnetic fields can reduce these resonance frequencies. We compute the ac and dc inverse spin Hall voltages resulting from dynamical spin excitations as a function of a magnetic field along the easy axis and the polarization of the driving ac magnetic field perpendicular to the easy axis. We consider the insulating antiferromagnets MnF2,FeF2, and NiO. Near the spin-flop transition, there is a significant enhancement of the dc spin pumping and inverse spin Hall voltage for the uniaxial antiferromagnets MnF2 and FeF2. In the uniaxial antiferromagnets it is also found that the ac spin pumping is independent of the external magnetic field when the driving field has the optimal circular polarization. In the biaxial NiO, the voltages are much weaker, and there is no spin-flop enhancement of the dc component.

Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

NASA Astrophysics Data System (ADS)

Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

2012-06-01

Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

NASA Astrophysics Data System (ADS)

Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

2012-05-01

Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

Alternating current (AC) iontophoretic transport across human epidermal membrane: effects of AC frequency and amplitude.

PubMed

Yan, Guang; Xu, Qingfang; Anissimov, Yuri G; Hao, Jinsong; Higuchi, William I; Li, S Kevin

2008-03-01

As a continuing effort to understand the mechanisms of alternating current (AC) transdermal iontophoresis and the iontophoretic transport pathways in the stratum corneum (SC), the objectives of the present study were to determine the interplay of AC frequency, AC voltage, and iontophoretic transport of ionic and neutral permeants across human epidermal membrane (HEM) and use AC as a means to characterize the transport pathways. Constant AC voltage iontophoresis experiments were conducted with HEM in 0.10 M tetraethyl ammonium pivalate (TEAP). AC frequencies ranging from 0.0001 to 25 Hz and AC applied voltages of 0.5 and 2.5 V were investigated. Tetraethyl ammonium (TEA) and arabinose (ARA) were the ionic and neutral model permeants, respectively. In data analysis, the logarithm of the permeability coefficients of HEM for the model permeants was plotted against the logarithm of the HEM electrical resistance for each AC condition. As expected, linear correlations between the logarithms of permeability coefficients and the logarithms of resistances of HEM were observed, and the permeability data were first normalized and then compared at the same HEM electrical resistance using these correlations. Transport enhancement of the ionic permeant was significantly larger than that of the neutral permeant during AC iontophoresis. The fluxes of the ionic permeant during AC iontophoresis of 2.5 V in the frequency range from 5 to 1,000 Hz were relatively constant and were approximately 4 times over those of passive transport. When the AC frequency decreased from 5 to 0.001 Hz at 2.5 V, flux enhancement increased to around 50 times over passive transport. While the AC frequency for achieving the full effect of iontophoretic enhancement at low AC frequency was lower than anticipated, the frequency for approaching passive diffusion transport at high frequency was higher than expected from the HEM morphology. These observations are consistent with a transport model of multiple barriers in series and the previous hypothesis that the iontophoresis pathways across HEM under AC behave like a series of reservoirs interconnected by short pore pathways.

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

PubMed

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

AC motor controller with 180 degree conductive switches

NASA Technical Reports Server (NTRS)

Oximberg, Carol A. (Inventor)

1995-01-01

An ac motor controller is operated by a modified time-switching scheme where the switches of the inverter are on for electrical-phase-and-rotation intervals of 180.degree. as opposed to the conventional 120.degree.. The motor is provided with three-phase drive windings, a power inverter for power supplied from a dc power source consisting of six switches, and a motor controller which controls the current controlled switches in voltage-fed mode. During full power, each switch is gated continuously for three successive intervals of 60.degree. and modulated for only one of said intervals. Thus, during each 60.degree. interval, the two switches with like signs are on continuously and the switch with the opposite sign is modulated.

Demonstration of an ac Josephson junction laser

NASA Astrophysics Data System (ADS)

Cassidy, M. C.; Bruno, A.; Rubbert, S.; Irfan, M.; Kammhuber, J.; Schouten, R. N.; Akhmerov, A. R.; Kouwenhoven, L. P.

2017-03-01

Superconducting electronic devices have reemerged as contenders for both classical and quantum computing due to their fast operation speeds, low dissipation, and long coherence times. An ultimate demonstration of coherence is lasing. We use one of the fundamental aspects of superconductivity, the ac Josephson effect, to demonstrate a laser made from a Josephson junction strongly coupled to a multimode superconducting cavity. A dc voltage bias applied across the junction provides a source of microwave photons, and the circuit’s nonlinearity allows for efficient down-conversion of higher-order Josephson frequencies to the cavity’s fundamental mode. The simple fabrication and operation allows for easy integration with a range of quantum devices, allowing for efficient on-chip generation of coherent microwave photons at low temperatures.

Direct current power delivery system and method

DOEpatents

Zhang, Di; Garces, Luis Jose; Dai, Jian; Lai, Rixin

2016-09-06

A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

Diagnostics of AC excited Atmospheric Pressure Plasma Jet with He for Biomedical Applications

NASA Astrophysics Data System (ADS)

Hori, Masaru; Takeda, Keigo; Kumakura, Takumi; Ishikawa, Kenji; Tanaka, Hiromasa; Kondo, Hiroki; Sekine, Makoto; Nakai, Yoshihiro

2014-10-01

Atmospheric pressure plasma jets (APPJ) are frequently used for biomedical applications. Reactive species generated by the APPJ play important roles for treatments of biomedical samples. Therefore, high density APPJ sources are required to realize the high performance. Our group has developed AC excited Ar APPJ with electron density as high as 1015 cm-3, and realized the selective killing of cancer cells and the inactivate spores of Penicillium digitatum. Recently, a new spot-size AC excited APPJ with He gas have been developed. In this study, the He APPJ was characterized by using spectroscopy. The plasma was discharged at a He flow rate of 5 slm and a discharge voltage of AC 9 kV. Gas temperature and electron density of the APPJ were measured by optical emission spectroscopy. From theoretical fitting of 2nd positive system of N2 emission (380.4 nm) and Stark broadening of Balmer β line of H atom (486.1 nm), the gas temperature and the electron density was estimated to be 299 K and 3.4. × 1015 cm-3. The AC excited He APPJ has a potential to realize high density with room temperature and become a very powerful tool for biomedical applications.

Design and implementation of co-operative control strategy for hybrid AC/DC microgrids

NASA Astrophysics Data System (ADS)

Mahmud, Rasel

This thesis is mainly divided in two major sections: 1) Modeling and control of AC microgrid, DC microgrid, Hybrid AC/DC microgrid using distributed co-operative control, and 2) Development of a four bus laboratory prototype of an AC microgrid system. At first, a distributed cooperative control (DCC) for a DC microgrid considering the state-of-charge (SoC) of the batteries in a typical plug-in-electric-vehicle (PEV) is developed. In DC microgrids, this methodology is developed to assist the load sharing amongst the distributed generation units (DGs), according to their ratings with improved voltage regulation. Subsequently, a DCC based control algorithm for AC microgrid is also investigated to improve the performance of AC microgrid in terms of power sharing among the DGs, voltage regulation and frequency deviation. The results validate the advantages of the proposed methodology as compared to traditional droop control of AC microgrid. The DCC-based control methodology for AC microgrid and DC microgrid are further expanded to develop a DCC-based power management algorithm for hybrid AC/DC microgrid. The developed algorithm for hybrid microgrid controls the power flow through the interfacing converter (IC) between the AC and DC microgrids. This will facilitate the power sharing between the DGs according to their power ratings. Moreover, it enables the fixed scheduled power delivery at different operating conditions, while maintaining good voltage regulation and improved frequency profile. The second section provides a detailed explanation and step-by-step design and development of an AC/DC microgrid testbed. Controllers for the three-phase inverters are designed and tested on different generation units along with their corresponding inductor-capacitor-inductor (LCL) filters to eliminate the switching frequency harmonics. Electric power distribution line models are developed to form the microgrid network topology. Voltage and current sensors are placed in the proper positions to achieve a full visibility over the microgrid. A running average filter (RAF) based enhanced phase-locked-loop (EPLL) is designed and implemented to extract frequency and phase angle information. A PLL-based synchronizing scheme is also developed to synchronize the DGs to the microgrid. The developed laboratory prototype runs on dSpace platform for real time data acquisition, communication and controller implementation.

High-frequency graphene voltage amplifier.

PubMed

Han, Shu-Jen; Jenkins, Keith A; Valdes Garcia, Alberto; Franklin, Aaron D; Bol, Ageeth A; Haensch, Wilfried

2011-09-14

While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date.

Analysis of a flux-coupling type superconductor fault current limiter with pancake coils

NASA Astrophysics Data System (ADS)

Liu, Shizhuo; Xia, Dong; Zhang, Zhifeng; Qiu, Qingquan; Zhang, Guomin

2017-10-01

The characteristics of a flux-coupling type superconductor fault current limiter (SFCL) with pancake coils are investigated in this paper. The conventional double-wound non-inductive pancake coil used in AC power systems has an inevitable defect in Voltage Sourced Converter Based High Voltage DC (VSC-HVDC) power systems. Due to its special structure, flashover would occur easily during the fault in high voltage environment. Considering the shortcomings of conventional resistive SFCLs with non-inductive coils, a novel flux-coupling type SFCL with pancake coils is carried out. The module connections of pancake coils are performed. The electromagnetic field and force analysis of the module are contrasted under different parameters. To ensure proper operation of the module, the impedance of the module under representative operating conditions is calculated. Finally, the feasibility of the flux-coupling type SFCL in VSC-HVDC power systems is discussed.

Performance analysis of radiation cooled dc transmission lines for high power space systems

NASA Technical Reports Server (NTRS)

Schwarze, G. E.

1985-01-01

As space power levels increase to meet mission objectives and also as the transmission distance between power source and load increases, the mass, volume, power loss, and operating voltage and temperature become important system design considerations. This analysis develops the dependence of the specific mass and percent power loss on hte power and voltage levels, transmission distance, operating temperature and conductor material properties. Only radiation cooling is considered since the transmission line is assumed to operate in a space environment. The results show that the limiting conditions for achieving low specific mass, percent power loss, and volume for a space-type dc transmission line are the permissible transmission voltage and operating temperature. Other means to achieve low specific mass include the judicious choice of conductor materials. The results of this analysis should be immediately applicable to power system trade-off studies including comparisons with ac transmission systems.

An Adaptive Coordinated Control for an Offshore Wind Farm Connected VSC Based Multi-Terminal DC Transmission System

NASA Astrophysics Data System (ADS)

Kumar, M. Ajay; Srikanth, N. V.

2015-01-01

The voltage source converter (VSC) based multiterminal high voltage direct current (MTDC) transmission system is an interesting technical option to integrate offshore wind farms with the onshore grid due to its unique performance characteristics and reduced power loss via extruded DC cables. In order to enhance the reliability and stability of the MTDC system, an adaptive neuro fuzzy inference system (ANFIS) based coordinated control design has been addressed in this paper. A four terminal VSC-MTDC system which consists of an offshore wind farm and oil platform is implemented in MATLAB/ SimPowerSystems software. The proposed model is tested under different fault scenarios along with the converter outage and simulation results show that the novel coordinated control design has great dynamic stabilities and also the VSC-MTDC system can supply AC voltage of good quality to offshore loads during the disturbances.

AC Resonant charger with charge rate unrelated to primary power frequency

DOEpatents

Watson, Harold

1982-01-01

An AC resonant charger for a capacitive load, such as a PFN, is provided with a variable repetition rate unrelated to the frequency of a multi-phase AC power source by using a control unit to select and couple the phase of the power source to the resonant charger in order to charge the capacitive load with a phase that is the next to begin a half cycle. For optimum range in repetition rate and increased charging voltage, the resonant charger includes a step-up transformer and full-wave rectifier. The next phase selected may then be of either polarity, but is always selected to be of a polarity opposite the polarity of the last phase selected so that the transformer core does not saturate. Thyristors are used to select and couple the correct phase just after its zero crossover in response to a sharp pulse generated by a zero-crossover detector. The thyristor that is turned on then automatically turns off after a full half cycle of its associated phase input. A full-wave rectifier couples the secondary winding of the transformer to the load so that the load capacitance is always charged with the same polarity.

Ac resonant charger with charge rate unrelated to preimary power requency

DOEpatents

Not Available

1979-12-07

An ac resonant charger for a capacitive load, such as a pulse forming network (PFN), is provided with a variable repetition rate unrelated to the frequency of a multi-phase ac power source by using a control unit to select and couple the phase of the power source to the resonant charger in order to charge the capacitive load with a phase that is the next to begin a half cycle. For optimum range in repetition rate and increased charging voltage, the resonant charger includes a step-up transformer and full-wave rectifier. The next phase selected may then be of either polarity, but is always selected to be of a polarity opposite the polarity of the last phase selected so that the transformer core does not saturate. Thyristors are used to select and couple the correct phase just after its zero crossover in response to a sharp pulse generated by a zero-crossover detector. The thyristor that is turned on then automatically turns off after a full half cycle of its associated phase input. A full-wave rectifier couples the secondary winding of the transformer to the load so that the load capacitance is always charged with the same polarity.

Equivalent circuit modeling of a piezo-patch energy harvester on a thin plate with AC-DC conversion

NASA Astrophysics Data System (ADS)

Bayik, B.; Aghakhani, A.; Basdogan, I.; Erturk, A.

2016-05-01

As an alternative to beam-like structures, piezoelectric patch-based energy harvesters attached to thin plates can be readily integrated to plate-like structures in automotive, marine, and aerospace applications, in order to directly exploit structural vibration modes of the host system without mass loading and volumetric occupancy of cantilever attachments. In this paper, a multi-mode equivalent circuit model of a piezo-patch energy harvester integrated to a thin plate is developed and coupled with a standard AC-DC conversion circuit. Equivalent circuit parameters are obtained in two different ways: (1) from the modal analysis solution of a distributed-parameter analytical model and (2) from the finite-element numerical model of the harvester by accounting for two-way coupling. After the analytical modeling effort, multi-mode equivalent circuit representation of the harvester is obtained via electronic circuit simulation software SPICE. Using the SPICE software, electromechanical response of the piezoelectric energy harvester connected to linear and nonlinear circuit elements are computed. Simulation results are validated for the standard AC-AC and AC-DC configurations. For the AC input-AC output problem, voltage frequency response functions are calculated for various resistive loads, and they show excellent agreement with modal analysis-based analytical closed-form solution and with the finite-element model. For the standard ideal AC input-DC output case, a full-wave rectifier and a smoothing capacitor are added to the harvester circuit for conversion of the AC voltage to a stable DC voltage, which is also validated against an existing solution by treating the single-mode plate dynamics as a single-degree-of-freedom system.

29 CFR 1926.97 - Electrical protective equipment.

Code of Federal Regulations, 2014 CFR

2014-07-01

... glove. (2) Electrical requirements. (i) Equipment shall be capable of withstanding the ac proof-test voltage specified in Table E-1 or the dc proof-test voltage specified in Table E-2. (A) The proof test shall reliably indicate that the equipment can withstand the voltage involved. (B) The test voltage...

An LMS Programming Scheme and Floating-Gate Technology Enabled Trimmer-Less and Low Voltage Flame Detection Sensor.

PubMed

Iglesias-Rojas, Juan Carlos; Gomez-Castañeda, Felipe; Moreno-Cadenas, Jose Antonio

2017-06-14

In this paper, a Least Mean Square (LMS) programming scheme is used to set the offset voltage of two operational amplifiers that were built using floating-gate transistors, enabling a 0.95 V RMS trimmer-less flame detection sensor. The programming scheme is capable of setting the offset voltage over a wide range of values by means of electron injection. The flame detection sensor consists of two programmable offset operational amplifiers; the first amplifier serves as a 26 μV offset voltage follower, whereas the second amplifier acts as a programmable trimmer-less voltage comparator. Both amplifiers form the proposed sensor, whose principle of functionality is based on the detection of the electrical changes produced by the flame ionization. The experimental results show that it is possible to measure the presence of a flame accurately after programming the amplifiers with a maximum of 35 LMS-algorithm iterations. Current commercial flame detectors are mainly used in absorption refrigerators and large industrial gas heaters, where a high voltage AC source and several mechanical trimmings are used in order to accurately measure the presence of the flame.

An LMS Programming Scheme and Floating-Gate Technology Enabled Trimmer-Less and Low Voltage Flame Detection Sensor

PubMed Central

Iglesias-Rojas, Juan Carlos; Gomez-Castañeda, Felipe; Moreno-Cadenas, Jose Antonio

2017-01-01

In this paper, a Least Mean Square (LMS) programming scheme is used to set the offset voltage of two operational amplifiers that were built using floating-gate transistors, enabling a 0.95 VRMS trimmer-less flame detection sensor. The programming scheme is capable of setting the offset voltage over a wide range of values by means of electron injection. The flame detection sensor consists of two programmable offset operational amplifiers; the first amplifier serves as a 26 μV offset voltage follower, whereas the second amplifier acts as a programmable trimmer-less voltage comparator. Both amplifiers form the proposed sensor, whose principle of functionality is based on the detection of the electrical changes produced by the flame ionization. The experimental results show that it is possible to measure the presence of a flame accurately after programming the amplifiers with a maximum of 35 LMS-algorithm iterations. Current commercial flame detectors are mainly used in absorption refrigerators and large industrial gas heaters, where a high voltage AC source and several mechanical trimmings are used in order to accurately measure the presence of the flame. PMID:28613250

A Ratiometric Method for Johnson Noise Thermometry Using a Quantized Voltage Noise Source

NASA Astrophysics Data System (ADS)

Nam, S. W.; Benz, S. P.; Martinis, J. M.; Dresselhaus, P.; Tew, W. L.; White, D. R.

2003-09-01

Johnson Noise Thermometry (JNT) involves the measurement of the statistical variance of a fluctuating voltage across a resistor in thermal equilibrium. Modern digital techniques make it now possible to perform many functions required for JNT in highly efficient and predictable ways. We describe the operational characteristics of a prototype JNT system which uses digital signal processing for filtering, real-time spectral cross-correlation for noise power measurement, and a digitally synthesized Quantized Voltage Noise Source (QVNS) as an AC voltage reference. The QVNS emulates noise with a constant spectral density that is stable, programmable, and calculable in terms of known parameters using digital synthesis techniques. Changes in analog gain are accounted for by alternating the inputs between the Johnson noise sensor and the QVNS. The Johnson noise power at a known temperature is first balanced with a synthesized noise power from the QVNS. The process is then repeated by balancing the noise power from the same resistor at an unknown temperature. When the two noise power ratios are combined, a thermodynamic temperature is derived using the ratio of the two QVNS spectral densities. We present preliminary results where the ratio between the gallium triple point and the water triple point is used to demonstrate the accuracy of the measurement system with a standard uncertainty of 0.04 %.

An AC electroosmotic micropump for circular chromatographic applications.

PubMed

Debesset, S; Hayden, C J; Dalton, C; Eijkel, J C T; Manz, A

2004-08-01

Flow rates of up to 50 microm s(-1) have been successfully achieved in a closed-loop channel using an AC electroosmotic pump. The AC electroosmotic pump is made of an interdigitated array of unequal width electrodes located at the bottom of a channel, with an AC voltage applied between the small and the large electrodes. The flow rate was found to increase linearly with the applied voltage and to decrease linearly with the applied frequency. The pump is expected to be suitable for circular chromatography for the following reasons: the driving forces are distributed over the channel length and the pumping direction is set by the direction of the interdigitated electrodes. Pumping in a closed-loop channel can be achieved by arranging the electrode pattern in a circle. In addition the inherent working principle of AC electroosmotic pumping enables the independent optimisation of the channel height or the flow velocity.

Non-oxidized porous silicon-based power AC switch peripheries.

PubMed

Menard, Samuel; Fèvre, Angélique; Valente, Damien; Billoué, Jérôme; Gautier, Gaël

2012-10-11

We present in this paper a novel application of porous silicon (PS) for low-power alternating current (AC) switches such as triode alternating current devices (TRIACs) frequently used to control small appliances (fridge, vacuum cleaner, washing machine, coffee makers, etc.). More precisely, it seems possible to benefit from the PS electrical insulation properties to ensure the OFF state of the device. Based on the technological aspects of the most commonly used AC switch peripheries physically responsible of the TRIAC blocking performances (leakage current and breakdown voltage), we suggest to isolate upper and lower junctions through the addition of a PS layer anodically etched from existing AC switch diffusion profiles. Then, we comment the voltage capability of practical samples emanating from the proposed architecture. Thanks to the characterization results of simple Al-PS-Si(P) structures, the experimental observations are interpreted, thus opening new outlooks in the field of AC switch peripheries.

Digital ac monitor

DOEpatents

Hart, George W.; Kern, Jr., Edward C.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

Digital ac monitor

DOEpatents

Hart, G.W.; Kern, E.C. Jr.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

Issues concerning centralized versus decentralized power deployment

NASA Technical Reports Server (NTRS)

Metcalf, Kenneth J.; Harty, Richard B.; Robin, James F.

1991-01-01

The results of a study of proposed lunar base architectures to identify issues concerning centralized and decentralized power system deployment options are presented. The power system consists of the energy producing system (power plant), the power conditioning components used to convert the generated power into the form desired for transmission, the transmission lines that conduct this power from the power sources to the loads, and the primary power conditioning hardware located at the user end. Three power system architectures, centralized, hybrid, and decentralized, were evaluated during the course of this study. Candidate power sources were characterized with respect to mass and radiator area. Two electrical models were created for each architecture to identify the preferred method of power transmission, dc or ac. Each model allowed the transmission voltage level to be varied at assess the impact on power system mass. The ac power system models also permitted the transmission line configurations and placements to determine the best conductor construction and installation location. Key parameters used to evaluate each configuration were power source and power conditioning component efficiencies, masses, and radiator areas; transmission line masses and operating temperatures; and total system mass.

Development of a solar charged laboratory bench power supply

NASA Astrophysics Data System (ADS)

Ayara, W. A.; Omotosho, T. V.; Usikalu, M. R.; Singh, M. S. J.; Suparta, W.

2017-05-01

This product is an improvement on available DC laboratory bench power supply. It is capable of delivering low voltage Alternating Current (AC) and Direct Current (DC) to carry out basic laboratory experiment for both secondary schools and also at higher education institutions. The power supply is capable of delivering fixed DC voltages of 5V, 9V, 12V, variable voltage of between 1.25-30V and a 12V AC voltage. Also Incorporated is a USB port that allows for charging cell phones and other mobile devices, and a dedicated 12V DC output to power 5-7 Watt LED bulb to provide illumination in the laboratory for the instructor who may need to work at night in the absence of utility power.

Development of software to improve AC power quality on large spacecraft

NASA Technical Reports Server (NTRS)

Kraft, L. Alan

1991-01-01

To insure the reliability of a 20 kHz, AC power system on spacecraft, it is essential to analyze its behavior under many adverse operating conditions. Some of these conditions include overloads, short circuits, switching surges, and harmonic distortions. Harmonic distortions can cause malfunctions in equipment that the power system is supplying, and during extreme distortions such as voltage resonance, it can cause equipment and insulation failures due to the extreme peak voltages. HARMFLO, a power flow computer program, which was capable of analyzing harmonic conditions on three phase, balanced, 60 Hz, AC power systems, was modified to analyze single phase, 20 kHz, AC power systems. Since almost all of the equipment used on spacecraft power systems is electrically different from equipment used on terrestrial power systems, it was also necessary to develop mathematical models for the equipment to be used on the spacecraft. The results are that (1) the harmonic power now has a model of a single phase, voltage controlled, full wave rectifier; and (2) HARMFLO was ported to the SUN workstation platform.

Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Bandler, Simon

2011-01-01

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

Analysis and Assessment of Operation Risk for Hybrid AC/DC Power System based on the Monte Carlo Method

NASA Astrophysics Data System (ADS)

Hu, Xiaojing; Li, Qiang; Zhang, Hao; Guo, Ziming; Zhao, Kun; Li, Xinpeng

2018-06-01

Based on the Monte Carlo method, an improved risk assessment method for hybrid AC/DC power system with VSC station considering the operation status of generators, converter stations, AC lines and DC lines is proposed. According to the sequential AC/DC power flow algorithm, node voltage and line active power are solved, and then the operation risk indices of node voltage over-limit and line active power over-limit are calculated. Finally, an improved two-area IEEE RTS-96 system is taken as a case to analyze and assessment its operation risk. The results show that the proposed model and method can intuitively and directly reflect the weak nodes and weak lines of the system, which can provide some reference for the dispatching department.

Alternating Current Driven Organic Light Emitting Diodes Using Lithium Fluoride Insulating Layers

PubMed Central

Liu, Shang-Yi; Chang, Jung-Hung; -Wen Wu, I.; Wu, Chih-I

2014-01-01

We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m2 obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage. PMID:25523436

System for transmitting low frequency analog signals over AC power lines

DOEpatents

Baker, Steven P.; Durall, Robert L.; Haynes, Howard D.

1989-01-01

A system for transmitting low frequency analog signals over AC power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an AC power line. The modulation signal frequency range in selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the AC power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal.

System for transmitting low frequency analog signals over AC power lines

DOEpatents

Baker, Steven P.; Durall, Robert L.; Haynes, Howard D.

1989-09-05

A system for transmitting low frequency analog signals over AC power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an AC power line. The modulation signal frequency range in selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the AC power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal.

A system for tranmitting low frequency analog signals over ac power lines

DOEpatents

Baker, S.P.; Durall, R.L.; Haynes, H.D.

1987-07-30

A system for transmitting low frequency analog signals over ac power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an ac power line. The modulation signal frequency range is selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the ac power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal. 4 figs.

Simulation of Trolleybus Traction Induction Drive With Supercapacitor Energy Storage System

NASA Astrophysics Data System (ADS)

Brazis, V.; Latkovskis, L.; Grigans, L.

2010-01-01

The article considers the possibilities of saving the regenerative braking energy in Škoda 24Tr type trolleybuses by installing the onboard supercapacitor energy storage system (ESS) and improving its performance with automated switching to the autonomous traction mode. Proposed is an ESS control system with constant DC bus voltage in the supercapacitor charging mode and supercapacitor current proportional to the AC drive current in the discharging mode. The authors investigate stability of the trolleybus ESS control system operating together with AC traction drive in various overhead voltage failure modes. The co-simulation of ESS operation was done by Matlab/Simulink AC drive and PSIM ESS continuous models.

Transmission Technologies and Operational Characteristic Analysis of Hybrid UHV AC/DC Power Grids in China

NASA Astrophysics Data System (ADS)

Tian, Zhang; Yanfeng, Gong

2017-05-01

In order to solve the contradiction between demand and distribution range of primary energy resource, Ultra High Voltage (UHV) power grids should be developed rapidly to meet development of energy bases and accessing of large-scale renewable energy. This paper reviewed the latest research processes of AC/DC transmission technologies, summarized the characteristics of AC/DC power grids, concluded that China’s power grids certainly enter a new period of large -scale hybrid UHV AC/DC power grids and characteristics of “strong DC and weak AC” becomes increasingly pro minent; possible problems in operation of AC/DC power grids was discussed, and interaction or effect between AC/DC power grids was made an intensive study of; according to above problems in operation of power grids, preliminary scheme is summarized as fo llows: strengthening backbone structures, enhancing AC/DC transmission technologies, promoting protection measures of clean energ y accessing grids, and taking actions to solve stability problems of voltage and frequency etc. It’s valuable for making hybrid UHV AC/DC power grids adapt to operating mode of large power grids, thus guaranteeing security and stability of power system.

Characteristics of long-gap AC streamer discharges under low pressure conditions

NASA Astrophysics Data System (ADS)

Yang, Yaqi; Li, Weiguo; Xia, Yu; Yuan, Chuangye

2017-10-01

The generation and propagation of a streamer is a significant physical process of air gap discharge. Research on the mechanism of streamers under low-pressure conditions is helpful for understanding the process of long-gap discharge in a high-altitude area. This paper describes laboratory investigations of streamer discharge under alternating current (AC) voltage in a low pressure test platform for a 60 cm rod-plane gap at 30 kPa, and analyzes the characteristics of streamer generation and propagation. The results show that the partial streamer and breakdown streamer all occur in the positive half-cycle of AC voltage near the peak voltage at 30 kPa. The partial streamer could cause the distortion of current and voltage waveform, and it appears as the branching characteristic at the initial stage. With the extension of the streamer, the branching and tortuosity phenomena become gradually obvious, but the branching is suppressed when the streamer crosses the gap. The low-pressure condition has little influence on the tortuosity length and the tortuosity number of the streamer, but affect the diameter of streamer obviously.

The role of optoelectronic feedback on Franz-Keldysh voltage modulation of transistor lasers

NASA Astrophysics Data System (ADS)

Chang, Chi-Hsiang; Chang, Shu-Wei; Wu, Chao-Hsin

2016-03-01

Possessing both the high-speed characteristics of heterojunction bipolar transistors (HBTs) and enhanced radiative recombination of quantum wells (QWs), the light-emitting transistor (LET) which operates in the regime of spontaneous emissions has achieved up to 4.3 GHz modulation bandwidth. A 40 Gbit/s transmission rate can be even achieved using transistor laser (TL). The transistor laser provides not only the current modulation but also direct voltage-controlled modulation scheme of optical signals via Franz-Keldysh (FK) photon-assisted tunneling effect. In this work, the effect of FK absorption on the voltage modulation of TLs is investigated. In order to analyze the dynamics and optical responses of voltage modulation in TLs, the conventional rate equations relevant to diode lasers (DLs) are first modified to include the FK effect intuitively. The theoretical results of direct-current (DC) and small-signal alternating-current (AC) characteristics of optical responses are both investigated. While the DC characteristics look physical, the intrinsic optical response of TLs under the FK voltage modulation shows an AC enhancement with a 20 dB peak, which however is not observed in experiment. A complete model composed of the intrinsic optical transfer function and an electrical transfer function fed back by optical responses is proposed to explain the behaviors of voltage modulation in TLs. The abnormal AC peak disappears through this optoelectronic feedback. With the electrical response along with FK-included photon-carrier rate equations taken into account, the complete voltage-controlled optical modulation response of TLs is demonstrated.

Simulation and Analysis of Three-Phase Rectifiers for Aerospace Power Applications

NASA Technical Reports Server (NTRS)

Truong, Long V.; Birchenough, Arthur G.

2004-01-01

Due to the nature of planned planetary missions, fairly large advanced power systems are required for the spacecraft. These future high power spacecrafts are expected to use dynamic power conversion systems incorporating high speed alternators as three-phase AC electrical power source. One of the early design considerations in such systems is the type of rectification to be used with the AC source for DC user loads. This paper address the issues involved with two different rectification methods, namely the conventional six and twelve pulses. Two circuit configurations which involved parallel combinations of the six and twelve-pulse rectifiers were selected for the simulation. The rectifier s input and output power waveforms will be thoroughly examined through simulations. The effects of the parasitic load for power balancing and filter components for reducing the ripple voltage at the DC loads are also included in the analysis. Details of the simulation circuits, simulation results, and design examples for reducing risk from damaging of spacecraft engines will be presented and discussed.

Neuronal responses to an asymmetrical alternating current field can mimic those produced by an imposed direct current field in vitro.

PubMed

Pan, Linjie; Cirillo, John; Borgens, Richard Ben

2012-08-01

The remarkable polarity-dependent growth and anatomical organization of neurons in vitro produced by imposed direct current (DC) voltage gradients (electrical fields; Ef) can be mimicked by another type of electrical cue. This is a properly structured asymmetrical alternating current (AC) electrical field (A-ACEf). Here we provide details on the construction of an AC signal generator in which all components of an AC waveform can be individually controlled. We show that 1) conventional symmetrical AC voltage gradients will not induce growth, guidance, or architectural changes in sympathetic neurons. We also provide the first qualitative and quantitative data showing that an asymmetric AC application can indeed mimic the DC response in chick sympathetic neurons and their growing neurites. This shift in orientation and neuronal anatomy requires dieback of some neurites and the extension of others to produce a preferred orientation perpendicular to the gradient of voltage. Our new results may lead to a noninvasive means to modify nerve growth and organization by magnetic inductive coupling at distance. These data also indicate the possibility of a means to mimic DC-dependent release of drugs or other biologically active molecules from electrically sensitive that can be loaded with these chemical cargos. Copyright © 2012 Wiley Periodicals, Inc.

Characterization of AC current sensor based on giant magnetoresistance and coil for power meter design

NASA Astrophysics Data System (ADS)

Dhani, H. S.; Aminudin, A.; Waslaluddin

2018-05-01

Electric current is the basic variable of measurement in instrumentation system. One of the current measurements had been developed was based on magnetic sensor. Giant Magnetoresistance (GMR) produces an output voltage when it detects the magnetic field from electric current flow. The purpose of this study was to characterize the response of GMR when variation number of coil was given. The characterization was the GMR voltage response to the AC current values from 0.01 A to 5.00 A. The linearity of the relation was reaching saturation point when the magnetic field measured higher than 10.5 Oe at room temperature. As the number of coil increased, the earlier saturation occurred. To see the sensitivity of the sensor response, the data graph was cut off at 1.56 A AC. From this research, we got single coil was ideal to measure electric current higher than 1.56 A AC, as the relation of GMR voltage to the current tended to maintain its linearity. For measurement of 1.56 A AC and less, coil number addition would increase the sensitivity of sensor response. This research hopefully will be benefit for further development using an electric current measurement based on GMR magnetic sensor for power meter design.

Steady-state analysis of a faulted three-phase four-wire system supplying induction motors with neutrals connected and other single-phase line-to-neutral loads

NASA Technical Reports Server (NTRS)

Wood, M. E.

1980-01-01

Four wire Wye connected ac power systems exhibit peculiar steady state fault characteristics when the fourth wire of three phase induction motors is connected. The loss of one phase of power source due to a series or shunt fault results in currents higher than anticipated on the remaining two phases. A theoretical approach to compute the fault currents and voltages is developed. A FORTRAN program is included in the appendix.

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link

PubMed Central

Lee, Hyung-Min; Ghovanloo, Maysam

2014-01-01

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35-μm 4-metal 2-poly standard CMOS process in 2.1 mm2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μF capacitors up to ±2 V in 420 μs, achieving a high measured charging efficiency of 82%. PMID:24678284

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link.

PubMed

Lee, Hyung-Min; Ghovanloo, Maysam

2013-10-01

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35- μ m 4-metal 2-poly standard CMOS process in 2.1 mm 2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μ F capacitors up to ±2 V in 420 μ s, achieving a high measured charging efficiency of 82%.

Analysis of improved dc and ac performances of an InGaP/GaAs heterojunction bipolar transistor with a graded Al xGa 1- xAs layer at emitter/base heterojunction

NASA Astrophysics Data System (ADS)

Cheng, Shiou-Ying

2004-07-01

An InGaP/GaAs heterojunction bipolar transistor (HBT) with a continuous conduction-band structure is demonstrated and theoretically investigated. This device exhibited good performance including lower turn-on voltage, lower offset voltage and smaller collector current saturation voltage. The novel aspect of device structure design is the adoption of the compositionally linear-graded AlGaAs layer between the InGaP-emitter and GaAs-base layers. Therefore, the device studied shows better dc and ac performances than a conventional device. Consequently, this causes the substantial benefit for practical analog and digital applications especially for lower operation voltage, lower power consumption commercial and military products.

Voltage balanced multilevel voltage source converter system

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

1997-01-01

A voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means.

Voltage balanced multilevel voltage source converter system

DOEpatents

Peng, F.Z.; Lai, J.S.

1997-07-01

Disclosed is a voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means. 15 figs.

Electric-Field Instrument With Ac-Biased Corona Point

NASA Technical Reports Server (NTRS)

Markson, R.; Anderson, B.; Govaert, J.

1993-01-01

Measurements indicative of incipient lightning yield additional information. New instrument gives reliable readings. High-voltage ac bias applied to needle point through high-resistance capacitance network provides corona discharge at all times, enabling more-slowly-varying component of electrostatic potential of needle to come to equilibrium with surrounding air. High resistance of high-voltage coupling makes instrument insensitive to wind. Improved corona-point instrument expected to yield additional information assisting in safety-oriented forecasting of lighting.

Enhanced Corrosion Resistance and Interfacial Conductivity of TiC x/a-C Nanolayered Coatings via Synergy of Substrate Bias Voltage for Bipolar Plates Applications in PEMFCs.

PubMed

Yi, Peiyun; Zhang, Weixin; Bi, Feifei; Peng, Linfa; Lai, Xinmin

2018-06-06

Proton-exchange membrane fuel cells are one kind of renewable and clean energy conversion device, whose metallic bipolar plates are one of the key components. However, high interfacial contact resistance and poor corrosion resistance are still great challenges for the commercialization of metallic bipolar plates. In this study, we demonstrated a novel strategy for depositing TiC x /amorphous carbon (a-C) nanolayered coatings by synergy of 60 and 300 V bias voltage to enhance corrosion resistance and interfacial conductivity. The synergistic effects of bias voltage on the composition, microstructure, surface roughness, electrochemical corrosion behaviors, and interfacial conductivity of TiC x /a-C coatings were explored. The results revealed that the columnar structures in the inner layer were suppressed and the surface became rougher with the 300 V a-C layer outside. The composition analysis indicated that the sp 2 content increased with an increase of 300 V sputtering time. Due to the synergy strategy of bias voltage, lower corrosion current densities were achieved both in potentiostatic polarization (1.6 V vs standard hydrogen electrode) and potentiodynamic polarization. With the increase of 300 V sputtering time, the interfacial conductivity was improved. The enhanced corrosion resistance and interfacial conductivity of the TiC x /a-C coatings would provide new opportunities for commercial bipolar plates.

Development of 2.8 V Ketjen black supercapacitors with high rate capabilities for AC line filtering

NASA Astrophysics Data System (ADS)

Yoo, Yongju; Park, Jinwoo; Kim, Min-Seop; Kim, Woong

2017-08-01

Supercapacitors are generally more compact than conventional bulky aluminum electrolytic capacitors (AECs). Replacement of AECs with supercapacitors can lead to miniaturization of electronic devices. However, even state-of-the-art supercapacitors developed in laboratories are superior to or competitive with AECs only in low voltage applications (<∼40 V). In order to improve the voltage limits of current supercapacitors, we have incorporated Ketjen black (KB) as an electrode material. Utilizing the open pore structure and the graphitic nature of KB, we demonstrate that the voltage limit can be extended to 53 V. The KB supercapacitor exhibits excellent areal capacitance, cell voltage, and phase angle values of ∼574 μF cm-2, 2.8 V, and ∼-80°, respectively. In addition, we demonstrate that an AC line filtering circuit with three supercapacitors connected in series can extend the application voltage without significant sacrifice in rate capability (ϕ ∼ -77° at 120 Hz). On the other hand, KBs are much less expensive than carbon materials previously demonstrated for AC line filtering and hence are very attractive for practical applications. We believe that this demonstration of high-performance supercapacitors made from low-cost carbon materials is both scientifically interesting and important for practical applications.

Moderately nonlinear diffuse-charge dynamics under an ac voltage.

PubMed

Stout, Robert F; Khair, Aditya S

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

The investigation of an electric arc in the long cylindrical channel of the powerful high-voltage AC plasma torch

NASA Astrophysics Data System (ADS)

Rutberg, Ph G.; Popov, S. D.; Surov, A. V.; Serba, E. O.; Nakonechny, Gh V.; Spodobin, V. A.; Pavlov, A. V.; Surov, A. V.

2012-12-01

The comparison of conductivity obtained in experiments with calculated values is made in this paper. Powerful stationary plasma torches with prolonged period of continuous work are popular for modern plasmachemical applications. The maximum electrode lifetime with the minimum erosion can be reached while working on rather low currents. Meanwhile it is required to provide voltage arc drop for the high power achievement. Electric field strength in the arc column of the high-voltage plasma torch, using air as a plasma-forming gas, does not exceed 15 V/cm. It is possible to obtain the high voltage drop in the long arc stabilized in the channel by the intensive gas flow under given conditions. Models of high voltage plasma torches with rod electrodes with power up to 50 kW have been developed and investigated. The plasma torch arcs are burning in cylindrical channels. Present investigations are directed at studying the possibility of developing long arc plasma torches with higher power. The advantage of AC power supplies usage is the possibility of the loss minimization due to the reactive power compensation. The theoretical maximum of voltage arc drop for power supplies with inductive current limitations is about 50 % of the no-load voltage for a single-phase circuit and about 30 % for the three-phase circuit. Burning of intensively blown arcs in the long cylindrical channel using the AC power supply with 10 kV no-load voltage is experimentally investigated in the work. Voltage drops close to the maximum possible had been reached in the examined arcs in single-phase and three-phase modes. Operating parameters for single-phase mode were: current -30 A, voltage drop -5 kV, air flow rate 35 g/s; for three-phase mode: current (40-85) A, voltage drop (2.5-3.2) kV, air flow rate (60-100) g/s. Arc length in the installations exceeded 2 m.

Hybrid inverter for HVDC/weak AC system interconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tam, K.S.

1985-01-01

The concept of the hybrid converter is introduced. By independently controlling a naturally commutated converter (NCC) and an artificially commutated converter (ACC), real power and reactive power can be controlled independently. Alternatively, the ac bus voltage can be regulated without affecting the real power transfer. Independent control is feasible only within certain operating boundaries. Twelve pulse operation, sequential control, and complementary circuits may be viewed as variations of the hybrid converter. The concept of the hybrid converter is demonstrated by digital simulation. At the current state of technology, the NCC is best implemented by a 6-pulse bridge using thyristors asmore » the switching elements. A survey of power electronics applicable to HVDC applications reveals that the capacitively commutated current-sourced converters are either technically or economically better than the other alternatives for the implementation of the ACC. The digital simulation results show that the problems of operating an HVDC system into a weak ac system can be solved by using a hybrid inverter. A new control scheme, the zero Q control, is developed. With no reactive power interaction between the dc system and the ac system, the stability of the HVDC/weak ac system operation is significantly improved. System start-up and fault recovery is fast and stable.« less

Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

NASA Astrophysics Data System (ADS)

Singh, B.; Shahani, D. T.; Verma, A. K.

2015-03-01

This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

Proofs for the Wave Theory of Plants

NASA Astrophysics Data System (ADS)

Wagner, Orvin E.

1997-03-01

Oscillatory behavior in plants. (2)Standing waves observed coming from probes equally spaced up tree trunks and freshly cut live wood samples. (3)Beat frequencies observed while applying AC voltages to plants. (4)Plant length quantization. (5)Plant growth angle and voltage quantization with respect to the gravitational field. (6)The measurement of plant frequences with a low frequency spectrum analyzer which correlate with the frequencies observed by other means such as by measuring plant lengths, considered as half wavelengths, and beat frequencies. (7)Voltages obtained from insulated, isolated from light, diode dies placed in slits in tree trunks. Diodes become relatively low impedance sources for voltages as high as eight volts. Diodes indicate charge separating longitudinal standing waves sweeping up and down a tree trunk. Longitudinal waves also indicated by plant structure. (8)The measured discrete wave velocities appear to be dependent on their direction of travel with respect to the gravitational field. These provide growth references for the plant and a wave guide affect. For references see Wagner Research Laboratory Web Page.

A Standalone Solar Photovoltaic Power Generation using Cuk Converter and Single Phase Inverter

NASA Astrophysics Data System (ADS)

Verma, A. K.; Singh, B.; Kaushika, S. C.

2013-03-01

In this paper, a standalone solar photovoltaic (SPV) power generating system is designed and modeled using a Cuk dc-dc converter and a single phase voltage source inverter (VSI). In this system, a dc-dc boost converter boosts a low voltage of a PV array to charge a battery at 24 V using a maximum power point tracking control algorithm. To step up a 24 V battery voltage to 360 V dc, a high frequency transformer based isolated dc-dc Cuk converter is used to reduce size, weight and losses. The dc voltage of 360 V is fed to a single phase VSI with unipolar switching to achieve a 230 Vrms, 50 Hz ac. The main objectives of this investigation are on efficiency improvement, reduction in cost, weight and size of the system and to provide an uninterruptible power to remotely located consumers. The complete SPV system is designed and it is modeled in MATLAB/Simulink. The simulated results are presented to demonstrate its satisfactory performance for validating the proposed design and control algorithm.

Capabilities of the new “Universal” AC-DC monitor for electropenetrography (EPG)

USDA-ARS?s Scientific Manuscript database

Electropenetrography (EPG), invented over 50 years ago, is the most rigorous and important means of studying the feeding of piercing-sucking crop pests. The 1st-generation monitor (or AC monitor) used AC applied signal voltage and had fixed amplifier sensitivity (input resistor or Ri) of 106 Ohms. T...

Faradaic AC Electrokinetic Flow and Particle Traps

NASA Astrophysics Data System (ADS)

Ben, Yuxing; Chang, Hsueh-Chia

2004-11-01

Faradaic reaction at higher voltages can produce co-ion polarization at AC electrodes instead of counter-ion polarization due to capacitive charging from the bulk. The Faradaic co-ion polarization also does not screen the external field and hence can produce large net electro-kinetic flows at frequencies lower than the inverse RC time of the double layer. Due to the opposite polarization of capacitve and Faradaic charging, we can reverse the direction of AC flows on electrodes by changing the voltage and frequency. Particles and bacteria are trapped and then dispersed at stagnation lines, at locations predicted by our theory, by using these two flows sequentially. This technique offers a good way to concentrate and detect bacteria.

Characterization and snubbing of a bidirectional MCT in a resonant ac link converter

NASA Technical Reports Server (NTRS)

Lee, Tony; Elbuluk, Malik E.; Zinger, Donald S.

1993-01-01

The MOS-Controlled Thyristor (MCT) is emerging as a powerful switch that combines the better characteristics of existing power devices. A study of switching stresses on an MCT switch under zero voltage resonant switching is presented. The MCT is used as a bidirectional switch in an ac/ac pulse density modulated inverter for induction motor drive. Current and voltage spikes are observed and analyzed with variations in the timing of the switching. Different snubber circuit configurations are under investigation to minimize the effect of these transients. The results will be extended to study and test the MCT switching in a medium power (5 hp) induction motor drive.

Impute DC link (IDCL) cell based power converters and control thereof

DOEpatents

Divan, Deepakraj M.; Prasai, Anish; Hernendez, Jorge; Moghe, Rohit; Iyer, Amrit; Kandula, Rajendra Prasad

2016-04-26

Power flow controllers based on Imputed DC Link (IDCL) cells are provided. The IDCL cell is a self-contained power electronic building block (PEBB). The IDCL cell may be stacked in series and parallel to achieve power flow control at higher voltage and current levels. Each IDCL cell may comprise a gate drive, a voltage sharing module, and a thermal management component in order to facilitate easy integration of the cell into a variety of applications. By providing direct AC conversion, the IDCL cell based AC/AC converters reduce device count, eliminate the use of electrolytic capacitors that have life and reliability issues, and improve system efficiency compared with similarly rated back-to-back inverter system.

Development of 50kV air-core transformer for electron gun static power source of 3MeV DC accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewangan, S.; Bakhtsingh, R.I.; Rajan, R.N.

A 3 MeV, 10 mA DC Electron Beam Accelerator based on the capacitively coupled parallel-fed voltage multiplier in 6 kg/cm{sup 2} SF{sub 6} gas environment is under commissioning at Electron Beam Centre, Kharghar, Navi Mumbai. Electron Gun is situated at -3 MV terminal which requires a constant power for its anode and filament. Gun power source has been derived by suitably coupling the ac components present in the HV Multiplier column. An aircore step down transformer rated for 50kV/600V/120kHz floating at 3 MV to extract the required power for electron gun from high voltage column has been developed. The transformermore » has been operated for 7 kW, 1 MeV of electron beam in 6 kg/cm{sup 2} nitrogen gas environment. The paper describes briefly about the design aspects and test results. (author)« less

A novel wireless power and data transmission AC to DC converter for an implantable device.

PubMed

Liu, Jhao-Yan; Tang, Kea-Tiong

2013-01-01

This article presents a novel AC to DC converter implemented by standard CMOS technology, applied for wireless power transmission. This circuit combines the functions of the rectifier and DC to DC converter, rather than using the rectifier to convert AC to DC and then supplying the required voltage with regulator as in the transitional method. This modification can reduce the power consumption and the area of the circuit. This circuit also transfers the loading condition back to the external circuit by the load shift keying(LSK), determining if the input power is not enough or excessive, which increases the efficiency of the total system. The AC to DC converter is fabricated with the TSMC 90nm CMOS process. The circuit area is 0.071mm(2). The circuit can produce a 1V DC voltage with maximum output current of 10mA from an AC input ranging from 1.5V to 2V, at 1MHz to 10MHz.

Design of a probe for two-dimensional small angle detection

NASA Astrophysics Data System (ADS)

He, Haixia; Wang, Xuanze; Zhong, Yuning; Yang, Liangen; Cao, Hongduan

2008-10-01

A novel two-dimensional small angle probe is introduced, which is based on principle of auto-collimation and utilizes quadrant Si-photoelectric detector (QPD) as detection device. AC modulation, AC magnification and absolute value demodulation are incorporated to restrain the DC excursion caused by background light and noise etc and to improve the sensitivity and stability of angle detection. To ensure that while the laser is shining, the current signal (converted into voltage signal) of QPD also is linear to the AC modulation voltage, this paper adopted AC modulation signal (5400Hz) with a DC offset. AC magnification circuit with reasonable parameters is designed to inhibit DC drift and the impact of industrial frequency noise and to ensure good amplification to signal frequency at the same time. A piezoelectric-driven micro-angle generator is designed to demarcate the angle. The calibration data are input to single chip, and the measurement of angles can be shown in SMC1602A.

75 FR 16957 - Energy Conservation Program: Test Procedures for Battery Chargers and External Power Supplies

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... Procedures C. Review of Single-Voltage External Power Supply Test Procedure D. Multiple-Voltage External...) Deletions of Existing Definitions (b) Revisions to Existing Definitions (c) Additions of New Definitions 4. Test Apparatus and General Instructions (a) Confidence Intervals (b) Temperature (c) AC Input Voltage...

Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

NASA Astrophysics Data System (ADS)

Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

Investigation of pumping mechanism for non-Newtonian blood flow with AC electrothermal forces in a microchannel by hybrid boundary element method and immersed boundary-lattice Boltzmann method.

PubMed

Ren, Qinlong

2018-02-10

Efficient pumping of blood flow in a microfluidic device is essential for rapid detection of bacterial bloodstream infections (BSI) using alternating current (AC) electrokinetics. Compared with AC electro-osmosis (ACEO) phenomenon, the advantage of AC electrothermal (ACET) mechanism is its capability of pumping biofluids with high electrical conductivities at a relatively high AC voltage frequency. In the current work, the microfluidic pumping of non-Newtonian blood flow using ACET forces is investigated in detail by modeling its multi-physics process with hybrid boundary element method (BEM) and immersed boundary-lattice Boltzmann method (IB-LBM). The Carreau-Yasuda model is used to simulate the realistic rheological behavior of blood flow. The ACET pumping efficiency of blood flow is studied in terms of different AC voltage magnitudes and frequencies, thermal boundary conditions of electrodes, electrode configurations, channel height, and the channel length per electrode pair. Besides, the effect of rheological behavior on the blood flow velocity is theoretically analyzed by comparing with the Newtonian fluid flow using scaling law analysis under the same physical conditions. The results indicate that the rheological behavior of blood flow and its frequency-dependent dielectric property make the pumping phenomenon of blood flow different from that of the common Newtonian aqueous solutions. It is also demonstrated that using a thermally insulated electrode could enhance the pumping efficiency dramatically. Besides, the results conclude that increasing the AC voltage magnitude is a more economical pumping approach than adding the number of electrodes with the same energy consumption when the Joule heating effect is acceptable. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy saving in ac generators

NASA Technical Reports Server (NTRS)

Nola, F. J.

1980-01-01

Circuit cuts no-load losses, without sacrificing full-load power. Phase-contro circuit includes gate-controlled semiconductor switch that cuts off applied voltage for most of ac cycle if generator idling. Switch "on" time increases when generator is in operation.

Tunable high-order-sideband generation and carrier-envelope-phase-dependent effects via microwave fields in hybrid electro-optomechanical systems

NASA Astrophysics Data System (ADS)

Si, Liu-Gang; Guo, Ling-Xia; Xiong, Hao; Wu, Ying

2018-02-01

We investigate the high-order-sideband generation (HSG) in a hybrid cavity electro-photomechanical system in which an optical cavity is driven by two optical fields (a monochromatic pump field and a nanosecond Gaussian probe pulse with huge numbers of wave cycles), and at the same time a microwave cavity is driven by a monochromatic ac voltage bias. We show that even if the input powers of two driven optical fields are comparatively low the HSG spectra can be induced and enhanced, and the sideband plateau is extended remarkably with the power of the ac voltage bias increasing. It is also shown that the driven ac voltage bias has profound effects on the carrier-envelope-phase-dependent effects of the HSG in the hybrid cavity electro-photomechanical system. Our research may provide an effective way to control the HSG of optical fields by using microwave fields in cavity optomechanics systems.

Bead-on-string structure printed by electrohydrodynamic jet under alternating current electric field

NASA Astrophysics Data System (ADS)

Liu, Juan; Lin, Yihuang; Jiang, Jiaxin; Liu, Haiyan; Zhao, Yang; Zheng, Gaofeng

2016-09-01

Electrohydrodynamic printing (EHDP) under alternating current (AC) electric field provides a novel way for the precise micro-/nano-droplet printing. The AC electric field induces the free charge to reciprocate along the EHDP jet and changes the electric field force on the jet periodically. The stability of jet can be enhanced by increasing the voltage frequency, and the regular bead-on-string structure is direct-written along the trajectory of collector. The deposition frequency of bead structure increases with the increasing of voltage frequency, due to the short period of AC electric field. As the voltage frequency is increased from 10 to 60 Hz, the diameter of bead structure decreases from 200 to 110 µm. As the duty ration increased from 10 to 60 %, the diameter of bead structure increased from 100 to 140 µm. This work would accelerate the development and the application of micro-/nano-printing technology in the fields of flexible electronic and micro-/nano-system.

AC resistance measuring instrument

DOEpatents

Hof, P.J.

1983-10-04

An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument. 8 figs.

AC Resistance measuring instrument

DOEpatents

Hof, Peter J.

1983-01-01

An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.

Dielectric breakdown strength of magnetic nanofluid based on insulation oil after impulse test

NASA Astrophysics Data System (ADS)

Nazari, M.; Rasoulifard, M. H.; Hosseini, H.

2016-02-01

In this study, the dielectric breakdown strength of magnetic nanofluids based on transformer mineral oil for use in power systems is reviewed. Nano oil samples are obtained from dispersion of the magnetic nanofluid within uninhibited transformer mineral oil NYTRO LIBRA as the base fluid. AC dielectric breakdown voltage measurement was carried out according to IEC 60156 standard and the lightning impulse breakdown voltage was obtained by using the sphere-sphere electrodes in an experimental setup for nano oil in volume concentration of 0.1-0.6%. Results indicate improved AC and lightning impulse breakdown voltage of nano oil compared to the base oil. AC test was performed again after applying impulse current and result showed that nano oil unlike the base oil retains its dielectric properties. Increase the dielectric strength of the nano oil is mainly due to dielectric and magnetic properties of Fe3O4 nanoparticles that act as free electrons snapper, and reduce the rate of free electrons in the ionization process.

Lateral separation of colloids or cells by dielectrophoresis augmented by AC electroosmosis.

PubMed

Zhou, Hao; White, Lee R; Tilton, Robert D

2005-05-01

Colloidal particles and biological cells are patterned and separated laterally adjacent to a micropatterned electrode array by applying AC electric fields that are principally oriented normally to the electrode array. This is demonstrated for yeast cells, red blood cells, and colloidal polystyrene particles of different sizes and zeta-potentials. The separation mechanism is observed experimentally to depend on the applied field frequency and voltage. At high frequencies, particles position themselves in a manner that is consistent with dielectrophoresis, while at low frequencies, the positioning is explained in terms of a strong coupling between gravity, the vertical component of the dielectrophoretic force, and the Stokes drag on particles induced by AC electroosmotic flow. Compared to high frequency dielectrophoretic separations, the low frequency separations are faster and require lower applied voltages. Furthermore, the AC electroosmosis coupling with dielectrophoresis may enable cell separations that are not feasible based on dielectrophoresis alone.

Adaptive Harmonic Detection Control of Grid Interfaced Solar Photovoltaic Energy System with Power Quality Improvement

NASA Astrophysics Data System (ADS)

Singh, B.; Goel, S.

2015-03-01

This paper presents a grid interfaced solar photovoltaic (SPV) energy system with a novel adaptive harmonic detection control for power quality improvement at ac mains under balanced as well as unbalanced and distorted supply conditions. The SPV energy system is capable of compensation of linear and nonlinear loads with the objectives of load balancing, harmonics elimination, power factor correction and terminal voltage regulation. The proposed control increases the utilization of PV infrastructure and brings down its effective cost due to its other benefits. The adaptive harmonic detection control algorithm is used to detect the fundamental active power component of load currents which are subsequently used for reference source currents estimation. An instantaneous symmetrical component theory is used to obtain instantaneous positive sequence point of common coupling (PCC) voltages which are used to derive inphase and quadrature phase voltage templates. The proposed grid interfaced PV energy system is modelled and simulated in MATLAB Simulink and its performance is verified under various operating conditions.

Strongly nonlinear dynamics of electrolytes in large ac voltages.

PubMed

Højgaard Olesen, Laurits; Bazant, Martin Z; Bruus, Henrik

2010-07-01

We study the response of a model microelectrochemical cell to a large ac voltage of frequency comparable to the inverse cell relaxation time. To bring out the basic physics, we consider the simplest possible model of a symmetric binary electrolyte confined between parallel-plate blocking electrodes, ignoring any transverse instability or fluid flow. We analyze the resulting one-dimensional problem by matched asymptotic expansions in the limit of thin double layers and extend previous work into the strongly nonlinear regime, which is characterized by two features--significant salt depletion in the electrolyte near the electrodes and, at very large voltage, the breakdown of the quasiequilibrium structure of the double layers. The former leads to the prediction of "ac capacitive desalination" since there is a time-averaged transfer of salt from the bulk to the double layers, via oscillating diffusion layers. The latter is associated with transient diffusion limitation, which drives the formation and collapse of space-charge layers, even in the absence of any net Faradaic current through the cell. We also predict that steric effects of finite ion sizes (going beyond dilute-solution theory) act to suppress the strongly nonlinear regime in the limit of concentrated electrolytes, ionic liquids, and molten salts. Beyond the model problem, our reduced equations for thin double layers, based on uniformly valid matched asymptotic expansions, provide a useful mathematical framework to describe additional nonlinear responses to large ac voltages, such as Faradaic reactions, electro-osmotic instabilities, and induced-charge electrokinetic phenomena.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milkov, Mihail M.

A comparator circuit suitable for use in a column-parallel single-slope analog-to-digital converter comprises a comparator, an input voltage sampling switch, a sampling capacitor arranged to store a voltage which varies with an input voltage when the sampling switch is closed, and a local ramp buffer arranged to buffer a global voltage ramp applied at an input. The comparator circuit is arranged such that its output toggles when the buffered global voltage ramp exceeds the stored voltage. Both DC- and AC-coupled comparator embodiments are disclosed.

Development of a Portable AC/DC Welding Power Supply Module

DTIC Science & Technology

1975-03-01

REPORT DATE MAR 1975 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Development of a Portable AC /DC Welding Power Supply...achieved. Additional bypass capacitors were added to reduce further switch heating and voltage transients. November AC welding was achieved with...Investigate the conversion of inversion frequency back to 60 Hz for AC welding. 4) Investigate a 120V single phase mini supply. VI I Objectives A) Goals

A new infusion pathway monitoring system utilizing electrostatic induced potential.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sada, Kouji; Hamada, Shingo; Hahn, Alien W; Caldwell, W Morton

2006-01-01

We have developed a new infusion pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer. The system is available for hospital and home use and it constantly monitors the intactness of the pathway. The sensor is an electro-conductive polymer electrode wrapped around the infusion polyvinyl chloride infusion tube. This records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltage and alerts the nursing station, via the nurse call system or PHS (personal handy phone System).

Lower-Order Compensation Chain Threshold-Reduction Technique for Multi-Stage Voltage Multipliers.

PubMed

Dell' Anna, Francesco; Dong, Tao; Li, Ping; Wen, Yumei; Azadmehr, Mehdi; Casu, Mario; Berg, Yngvar

2018-04-17

This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs) powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control of the trade-off among transistor conductivity and leakage losses, is aimed at maximizing the voltage conversion efficiency (VCE) for a given ac input signal and physical chip area occupation. The conducted simulations positively assert the validity of the proposed design methodology, emphasizing the exploitable design space yielded by the transistor connection scheme in the voltage multiplier chain. An experimental validation and comparison of threshold-compensation techniques was performed, adopting 2N5247 N-channel junction field effect transistors (JFETs) for the realization of the voltage multiplier prototypes. The attained measurements clearly support the effectiveness of the proposed threshold-reduction approach, which can significantly reduce the chip area occupation for a given target output performance and ac input signal.

Performance characteristics of lithium primary cells after controlled storage. [on-orbit for energy power supply

NASA Technical Reports Server (NTRS)

Deligiannis, F.; Shen, D. H.; Halpert, G.; Ang, V.; Donley, S.

1991-01-01

A program was initiated to investigate the effects of storage on the performance of lithium primary cells. Two types of liquid cathode cells were chosen to investigate these effects. The cell types included Li-SOCl2/BCX cells, Li-SO2 cells from two different manufacturers, and a small sample size of 8-year-old Li-SO2 cells. The following measurements are performed at each test interval: open circuit voltage, resistance and weight, microcalorimetry, ac impedance, capacity, and voltage delay. The authors examine the performance characteristics of these cells after one year of controlled storage at two temperatures (10 and 30 C). The Li-SO2 cells experienced little to no voltage and capacity degradation after one year storage. The Li-SOCl2/BCX cells exhibited significant voltage and capacity degradation after 30 C storage. Predischarging shortly prior to use appears to be an effective method of reducing the initial voltage drop. Studies are in progress to correlate ac impedance and microcalorimetry measurements with capacity losses and voltage delay.

General analytical solutions for DC/AC circuit-network analysis

NASA Astrophysics Data System (ADS)

Rubido, Nicolás; Grebogi, Celso; Baptista, Murilo S.

2017-06-01

In this work, we present novel general analytical solutions for the currents that are developed in the edges of network-like circuits when some nodes of the network act as sources/sinks of DC or AC current. We assume that Ohm's law is valid at every edge and that charge at every node is conserved (with the exception of the source/sink nodes). The resistive, capacitive, and/or inductive properties of the lines in the circuit define a complex network structure with given impedances for each edge. Our solution for the currents at each edge is derived in terms of the eigenvalues and eigenvectors of the Laplacian matrix of the network defined from the impedances. This derivation also allows us to compute the equivalent impedance between any two nodes of the circuit and relate it to currents in a closed circuit which has a single voltage generator instead of many input/output source/sink nodes. This simplifies the treatment that could be done via Thévenin's theorem. Contrary to solving Kirchhoff's equations, our derivation allows to easily calculate the redistribution of currents that occurs when the location of sources and sinks changes within the network. Finally, we show that our solutions are identical to the ones found from Circuit Theory nodal analysis.

Electrical quantum standards and their role in the SI

NASA Astrophysics Data System (ADS)

Robinson, Ian; Georgakopoulos, Dimitrios

2012-12-01

The International System of Units, SI, is poised to make a quantum change and become a measurement system based entirely on the fundamental properties of the natural world. In the next version of the SI, the Planck constant h, the elementary charge e, the Avogadro constant NA and the Boltzmann constant k will be fixed, in addition to the already fixed values of the speed of light c and the ground state hyperfine splitting in caesium-133. As a result, six out of the seven base units of the SI will be based directly on true invariants of nature. A major part of this change has been enabled by the ready availability of electrical quantum standards of exquisite precision and mechanisms for using them to make measurements outside the electrical arena. The overall effect will be to eliminate the remaining imprecise definitions of physical units associated with the use of artefact standards and aid direct SI measurements without problems of scaling. Fixing the Planck constant and the elementary charge will have the effect of incorporating the best physical realizations of electrical quantities into the SI, providing a system of units fit for the 21st century. The purpose of this special feature is to review the status of electrical quantum standards and report the latest developments in those areas and their applications to other areas of metrology. The special feature coincides with the 50th anniversary of the seminal paper of Josephson, 'Possible new effects in superconductive tunnelling' [1], which established the basic physical principle upon which the quantum voltage standards are based. Josephson voltage standards are based on the inverse Josephson effect. When a junction of two superconducting electrodes, weakly linked through a thin insulator or a normal metal, is irradiated with a radiofrequency electromagnetic field of frequency f and is biased by a dc current, then the voltage across the junction is quantized (i.e. small changes in either the dc current or the power of the rf irradiation, or both, do not change the voltage). The value of this quantized Josephson voltage is equal to nfh/2e, where n is the quantum step of the current-voltage characteristic curve. In this special feature there are three papers on dc Josephson voltage standards. Solve and Stock review the programme conducted by the Bureau International des Poids et Mesures (BIPM) to perform on-site comparisons of Josephson voltage standards, and give a comprehensive analysis of the possible sources of errors of such comparisons. Behr et al summarize the developments of Josephson voltage standards at Physikalisch-Technische Bundesanstalt (PTB) and their applications in dc voltage and other areas of metrology. Finally, Georgakopoulos et al report a reduction, by a factor of a thousand, in the smallest voltage that can be generated by dc Josephson voltage standards. Although dc voltage standards are well established, significant challenges exist when extending this extremely precise technology to ac. There are two approaches to producing accurate ac voltages using the inverse Josephson effect: the programmable Josephson voltage standard (PJVS) and the pulse-driven ac voltage standard. The PJVS contains an array of Josephson junctions, organized into independently biased segments. By biasing chosen, binary-related, segments on the first quantum step (positive or negative) or zero, the array can be made to behave as a quantum digital to analogue converter. The PJVS approach can produce stepwise approximated sine waves with rms values of some volts, but it suffers from parasitic capacitances and inductances distributed in the different parts of the system and, more importantly, the voltage is not quantized during the finite transition time between successive voltage levels. Hence the output frequency of PJVS-based systems is limited to a few kilohertz. In this special feature, Jeanneret et al review the Josephson locked synthesizer, a PJVS-based system where the effect of transients between successive steps on the output voltage is reduced. This special feature also presents two applications of PJVS-based quantum voltage standards: the evaluation of conventional ac voltage standards based on thermal converters (Budovsky et al) and the measurement of the settling time of a high resolution digital voltmeter (Henderson et al). In the pulse-driven ac voltage standard, arbitrary voltages can be produced by modulating the rf irradiation of an array of Josephson junctions by a series of high frequency pulses, usually by means of Δ-Σ modulation. The output voltage of the array of junctions is a series of quantized voltage pulses that correspond to the desired waveform after the high frequency components are removed. The pulse-driven standard can operate at much higher frequencies than the PJVS. Eliminating the effects of parasitic impedances of the, necessarily long, connecting leads therefore becomes a significant challenge. In this special feature, van den Brom and Houtzager report a voltage lead correction technique. Quantum resistance standards are based on the quantum Hall effect in which the resistance of a two-dimensional electron gas in a strong magnetic field is quantized. The value of the quantized Hall resistance is h/ie2, where i is the number of the quantum step in the resistance-magnetic field curve. Quantum Hall resistance devices can be combined in series to form a resistive voltage divider with low uncertainty in the ratio. In this special feature, Domae et al report the realization of such a resistive voltage divider on a chip. Quantum Hall resistance standards have been routinely used at dc for over two decades. However, the operation of quantum Hall devices at ac is complicated by the flow of current in capacitances around the device, which can compromise measurement of its resistance. Schurr et al review the status of ac quantum Hall resistance standards and their role in the SI. Ohm's law can be applied to quantum realizations of voltage, resistance and current to test their consistency. Active research into this 'metrological triangle' is underway and, at present, there is no evidence to indicate a discrepancy at any level. However, work is continuing on current sources which utilize a countable flow of electrons (the electric current produced is proportional to ef, f being the operating frequency of the device), but the work has some way to go before the question of consistency can be resolved at levels approaching 1 part in 109. In this special feature, Scherer and Camarota review the state-of-the-art of metrological triangle experiments and Devoille et al report on the status of the metrological triangle experiment at the Laboratoire National de Métrologie et d'Essais (LNE), France. The availability of precise representations of the volt and the ohm based on quantum mechanics has enabled the watt balance, an apparatus which relates electrical and mechanical power, to link the kilogram to the Planck constant. This has paved the way for the proposed redefinition of the kilogram, the last artefact standard in the SI, in terms of a fixed value of the Planck constant. In the past few years a number of papers, e.g. [2, 3], have been published describing the working principles of the watt balance and the characteristics of the existing implementations of the experiment. The measurements of the principal quantities—mass, velocity, gravitational acceleration, resistance and voltage—are reasonably well documented but the ultimate precision of the apparatus depends on a number of techniques that are required to eliminate second-order effects. In this special feature, Robinson provides details of these general alignment techniques with special reference to the NPL Mark II watt balance. Acknowledgments We would like to thank the authors for supporting the special feature with their excellent contributions; the guardians of the quality of a scientific paper, the referees, for their valuable comments and suggestions; Professor Wuqiang Yang and the members of the editorial board of Measurement Science and Technology for their support. Finally, we would like to thank Dr Sharon D'Souza, James Dimond and all the editorial and publication staff at Measurement Science and Technology, for their help in making the special feature a reality. References [1] Josephson B D 1962 Possible new effects in superconductive tunnelling Phys. Lett. 1 251-3 [2] Li S, Han B, Li Z and Lan J 2012 Precisely measuring the Planck constant by electromechanical balances Measurement 45 1-13 [3] Stock M 2011 The watt balance: determination of the Planck constant and redefinition of the kilogram Phil. Trans. R. Soc. A 369 3936-53

A randomized trial of the effect of automated ventricular capture on device longevity and threshold measurement in pacemaker patients.

PubMed

Koplan, Bruce A; Gilligan, David M; Nguyen, Luc S; Lau, Theodore K; Thackeray, Lisa M; Berg, Kellie Chase

2008-11-01

An automatic capture (AC) algorithm adjusts ventricular pacing output to capture the ventricle while optimizing output to 0.5 V above threshold. AC maintains this output and confirms capture on a beat-to-beat basis in bipolar and unipolar pacing and sensing. To assess the AC algorithm and its impact on device longevity. Patients implanted with a pacemaker were randomized 1:1 to have the AC feature on or off for 12 months. Two threshold tests were conducted at each visit- automatic threshold and manual threshold. Average ventricular voltage output and projected device longevity were compared between AC on and off using nonparametric tests. Nine hundred ten patients were enrolled and underwent device implantation. Average ventricular voltage output was 1.6 V for the AC on arm (n = 444) and 3.1 V for the AC off arm (n = 446) (P < 0.001). Projected device longevity was 10.3 years for AC on and 8.9 years for AC off (P < 0.0001), or a 16% increase in longevity for AC on. The proportion of patients in whom there was a difference between automatic threshold and manual threshold of

Working group report on advanced high-voltage high-power and energy-storage space systems

NASA Technical Reports Server (NTRS)

Cohen, H. A.; Cooke, D. L.; Evans, R. W.; Hastings, D.; Jongeward, G.; Laframboise, J. G.; Mahaffey, D.; Mcintyre, B.; Pfizer, K. A.; Purvis, C.

1986-01-01

Space systems in the future will probably include high-voltage, high-power energy-storage and -production systems. Two such technologies are high-voltage ac and dc systems and high-power electrodynamic tethers. The working group identified several plasma interaction phenomena that will occur in the operation of these power systems. The working group felt that building an understanding of these critical interaction issues meant that several gaps in our knowledge had to be filled, and that certain aspects of dc power systems have become fairly well understood. Examples of these current collection are in quiescent plasmas and snap over effects. However, high-voltage dc and almost all ac phenomena are, at best, inadequately understood. In addition, there is major uncertainty in the knowledge of coupling between plasmas and large scale current flows in space plasmas. These gaps in the knowledge are addressed.

Research on key technology of planning and design for AC/DC hybrid distribution network

NASA Astrophysics Data System (ADS)

Shen, Yu; Wu, Guilian; Zheng, Huan; Deng, Junpeng; Shi, Pengjia

2018-04-01

With the increasing demand of DC generation and DC load, the development of DC technology, AC and DC distribution network integrating will become an important form of future distribution network. In this paper, the key technology of planning and design for AC/DC hybrid distribution network is proposed, including the selection of AC and DC voltage series, the design of typical grid structure and the comprehensive evaluation method of planning scheme. The research results provide some ideas and directions for the future development of AC/DC hybrid distribution network.

Critical frequency for coalescence of emulsions in an AC electric field

NASA Astrophysics Data System (ADS)

Liu, Zhou; Ali, Faizi Hammad; Shum, Ho Cheung

2017-11-01

Applying an electric field to trigger the coalescence of emulsions has been applied in various applications which include crude oil recovery, emulsion stability characterization as well as pico-injection and droplet-based chemical reaction in microfluidics. In this work, we systematically investigated the responses of surfactant-stabilized emulsions to a controlled AC electric field using a customer-built chip. At a given amplitude of the AC voltage, we found a critical frequency beyond which the emulsions remain stable. When the frequency is decreased to below the critical value, emulsions coalesce immediately. Such critical frequency is found to be dependent of amplitude of the AC voltage, viscosity of the fluids, concentration and type of the surfactant as well as the electric conductivity of the droplet phase. Using a model based on the drainage of thin film, we have explored the mechanism behind and interpret this phenomenon systematically. Our work extends the understanding of the electro-coalescence of emulsions and can be beneficial for any applications involve the coalescence of droplets in an AC electric field.

Carbon Nanotube Tape Vibrating Gyroscope

NASA Technical Reports Server (NTRS)

Tucker, Dennis Stephen (Inventor)

2016-01-01

A vibrating gyroscope includes a piezoelectric strip having length and width dimensions. The piezoelectric strip includes a piezoelectric material and carbon nanotubes (CNTs) substantially aligned and polled along the strip's length dimension. A spindle having an axis of rotation is coupled to the piezoelectric strip. The axis of rotation is parallel to the strip's width dimension. A first capacitance sensor is mechanically coupled to the spindle for rotation therewith. The first capacitance sensor is positioned at one of the strip's opposing ends and is spaced apart from one of the strip's opposing faces. A second capacitance sensor is mechanically coupled to the spindle for rotation therewith. The second capacitance sensor is positioned at another of the strip's opposing ends and is spaced apart from another of the strip's opposing faces. A voltage source applies an AC voltage to the piezoelectric strip.

Standard deviation of the mean and other time series properties of voltages measured with a digital lock-in amplifier

NASA Astrophysics Data System (ADS)

Witt, Thomas J.; Fletcher, N. E.

2010-10-01

We investigate some statistical properties of ac voltages from a white noise source measured with a digital lock-in amplifier equipped with finite impulse response output filters which introduce correlations between successive voltage values. The main goal of this work is to propose simple solutions to account for correlations when calculating the standard deviation of the mean (SDM) for a sequence of measurement data acquired using such an instrument. The problem is treated by time series analysis based on a moving average model of the filtering process. Theoretical expressions are derived for the power spectral density (PSD), the autocorrelation function, the equivalent noise bandwidth and the Allan variance; all are related to the SDM. At most three parameters suffice to specify any of the above quantities: the filter time constant, the time between successive measurements (both set by the lock-in operator) and the PSD of the white noise input, h0. Our white noise source is a resistor so that the PSD is easily calculated; there are no free parameters. Theoretical expressions are checked against their respective sample estimates and, with the exception of two of the bandwidth estimates, agreement to within 11% or better is found.

Optimal Power Scheduling for a Medium Voltage AC/DC Hybrid Distribution Network

DOE PAGES

Zhu, Zhenshan; Liu, Dichen; Liao, Qingfen; ...

2018-01-26

With the great increase of renewable generation as well as the DC loads in the distribution network; DC distribution technology is receiving more attention; since the DC distribution network can improve operating efficiency and power quality by reducing the energy conversion stages. This paper presents a new architecture for the medium voltage AC/DC hybrid distribution network; where the AC and DC subgrids are looped by normally closed AC soft open point (ACSOP) and DC soft open point (DCSOP); respectively. The proposed AC/DC hybrid distribution systems contain renewable generation (i.e., wind power and photovoltaic (PV) generation); energy storage systems (ESSs); softmore » open points (SOPs); and both AC and DC flexible demands. An energy management strategy for the hybrid system is presented based on the dynamic optimal power flow (DOPF) method. The main objective of the proposed power scheduling strategy is to minimize the operating cost and reduce the curtailment of renewable generation while meeting operational and technical constraints. The proposed approach is verified in five scenarios. The five scenarios are classified as pure AC system; hybrid AC/DC system; hybrid system with interlinking converter; hybrid system with DC flexible demand; and hybrid system with SOPs. Results show that the proposed scheduling method can successfully dispatch the controllable elements; and that the presented architecture for the AC/DC hybrid distribution system is beneficial for reducing operating cost and renewable generation curtailment.« less

Optimal Power Scheduling for a Medium Voltage AC/DC Hybrid Distribution Network

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Zhenshan; Liu, Dichen; Liao, Qingfen

With the great increase of renewable generation as well as the DC loads in the distribution network; DC distribution technology is receiving more attention; since the DC distribution network can improve operating efficiency and power quality by reducing the energy conversion stages. This paper presents a new architecture for the medium voltage AC/DC hybrid distribution network; where the AC and DC subgrids are looped by normally closed AC soft open point (ACSOP) and DC soft open point (DCSOP); respectively. The proposed AC/DC hybrid distribution systems contain renewable generation (i.e., wind power and photovoltaic (PV) generation); energy storage systems (ESSs); softmore » open points (SOPs); and both AC and DC flexible demands. An energy management strategy for the hybrid system is presented based on the dynamic optimal power flow (DOPF) method. The main objective of the proposed power scheduling strategy is to minimize the operating cost and reduce the curtailment of renewable generation while meeting operational and technical constraints. The proposed approach is verified in five scenarios. The five scenarios are classified as pure AC system; hybrid AC/DC system; hybrid system with interlinking converter; hybrid system with DC flexible demand; and hybrid system with SOPs. Results show that the proposed scheduling method can successfully dispatch the controllable elements; and that the presented architecture for the AC/DC hybrid distribution system is beneficial for reducing operating cost and renewable generation curtailment.« less

Metal detector system

NASA Technical Reports Server (NTRS)

Lee, R. D.

1970-01-01

Signal voltage resulting from the disturbance of an electromagnetic field within the volume of a sensitive area is compared with a reference ac voltage for polarity information, which identifies the material. System output amplitude and polarity indicate approximate size and type of metal, respectively.

MultiElec: A MATLAB Based Application for MEA Data Analysis.

PubMed

Georgiadis, Vassilis; Stephanou, Anastasis; Townsend, Paul A; Jackson, Thomas R

2015-01-01

We present MultiElec, an open source MATLAB based application for data analysis of microelectrode array (MEA) recordings. MultiElec displays an extremely user-friendly graphic user interface (GUI) that allows the simultaneous display and analysis of voltage traces for 60 electrodes and includes functions for activation-time determination, the production of activation-time heat maps with activation time and isoline display. Furthermore, local conduction velocities are semi-automatically calculated along with their corresponding vector plots. MultiElec allows ad hoc signal suppression, enabling the user to easily and efficiently handle signal artefacts and for incomplete data sets to be analysed. Voltage traces and heat maps can be simply exported for figure production and presentation. In addition, our platform is able to produce 3D videos of signal progression over all 60 electrodes. Functions are controlled entirely by a single GUI with no need for command line input or any understanding of MATLAB code. MultiElec is open source under the terms of the GNU General Public License as published by the Free Software Foundation, version 3. Both the program and source code are available to download from http://www.cancer.manchester.ac.uk/MultiElec/.

Effects of surface dielectric barrier discharge on aerodynamic characteristic of train

NASA Astrophysics Data System (ADS)

Dong, Lei; Gao, Guoqiang; Peng, Kaisheng; Wei, Wenfu; Li, Chunmao; Wu, Guangning

2017-07-01

High-speed railway today has become an indispensable means of transportation due to its remarkable advantages, including comfortability, convenience and less pollution. The increase in velocity makes the air drag become the main source of energy consumption, leading to receiving more and more concerns. The surface dielectric barrier discharge has shown some unique characteristics in terms of active airflow control. In this paper, the influences of surface dielectric barrier discharge on the aerodynamic characteristics of a scaled train model have been studied. Aspects of the discharge power consumption, the temperature distribution, the velocity of induced flow and the airflow field around the train model were considered. The applied AC voltage was set in the range of 20 kV to 28 kV, with a fixed frequency of 9 kHz. Results indicated that the discharge power consumption, the maximum temperature and the induced flow velocity increased with increasing applied voltage. Mechanisms of applied voltage influencing these key parameters were discussed from the point of the equivalent circuit. The airflow field around the train model with different applied voltages was observed by the smoke visualization experiment. Finally, the effects of surface dielectric barrier discharge on the train drag reduction with different applied voltages were analyzed.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.;

The a.c. Josephson effect without superconductivity

PubMed Central

Gaury, Benoit; Weston, Joseph; Waintal, Xavier

2015-01-01

Superconductivity derives its most salient features from the coherence of the associated macroscopic wave function. The related physical phenomena have now moved from exotic subjects to fundamental building blocks for quantum circuits such as qubits or single photonic modes. Here we predict that the a.c. Josephson effect—which transforms a d.c. voltage Vb into an oscillating signal cos (2eVbt/ħ)—has a mesoscopic counterpart in normal conductors. We show that when a d.c. voltage Vb is applied to an electronic interferometer, there exists a universal transient regime where the current oscillates at frequency eVb/h. This effect is not limited by a superconducting gap and could, in principle, be used to produce tunable a.c. signals in the elusive 0.1–10-THz ‘terahertz gap’. PMID:25765929

A Power-Efficient Wireless System With Adaptive Supply Control for Deep Brain Stimulation.

PubMed

Lee, Hyung-Min; Park, Hangue; Ghovanloo, Maysam

2013-09-01

A power-efficient wireless stimulating system for a head-mounted deep brain stimulator (DBS) is presented. A new adaptive rectifier generates a variable DC supply voltage from a constant AC power carrier utilizing phase control feedback, while achieving high AC-DC power conversion efficiency (PCE) through active synchronous switching. A current-controlled stimulator adopts closed-loop supply control to automatically adjust the stimulation compliance voltage by detecting stimulation site potentials through a voltage readout channel, and improve the stimulation efficiency. The stimulator also utilizes closed-loop active charge balancing to maintain the residual charge at each site within a safe limit, while receiving the stimulation parameters wirelessly from the amplitude-shift-keyed power carrier. A 4-ch wireless stimulating system prototype was fabricated in a 0.5-μm 3M2P standard CMOS process, occupying 2.25 mm². With 5 V peak AC input at 2 MHz, the adaptive rectifier provides an adjustable DC output between 2.5 V and 4.6 V at 2.8 mA loading, resulting in measured PCE of 72 ~ 87%. The adaptive supply control increases the stimulation efficiency up to 30% higher than a fixed supply voltage to 58 ~ 68%. The prototype wireless stimulating system was verified in vitro .

A Power-Efficient Wireless System With Adaptive Supply Control for Deep Brain Stimulation

PubMed Central

Lee, Hyung-Min; Park, Hangue; Ghovanloo, Maysam

2014-01-01

A power-efficient wireless stimulating system for a head-mounted deep brain stimulator (DBS) is presented. A new adaptive rectifier generates a variable DC supply voltage from a constant AC power carrier utilizing phase control feedback, while achieving high AC-DC power conversion efficiency (PCE) through active synchronous switching. A current-controlled stimulator adopts closed-loop supply control to automatically adjust the stimulation compliance voltage by detecting stimulation site potentials through a voltage readout channel, and improve the stimulation efficiency. The stimulator also utilizes closed-loop active charge balancing to maintain the residual charge at each site within a safe limit, while receiving the stimulation parameters wirelessly from the amplitude-shift-keyed power carrier. A 4-ch wireless stimulating system prototype was fabricated in a 0.5-μm 3M2P standard CMOS process, occupying 2.25 mm². With 5 V peak AC input at 2 MHz, the adaptive rectifier provides an adjustable DC output between 2.5 V and 4.6 V at 2.8 mA loading, resulting in measured PCE of 72 ~ 87%. The adaptive supply control increases the stimulation efficiency up to 30% higher than a fixed supply voltage to 58 ~ 68%. The prototype wireless stimulating system was verified in vitro. PMID:24678126

Non-local detection of spin dynamics via spin rectification effect in yttrium iron garnet/SiO{sub 2}/NiFe trilayers near simultaneous ferromagnetic resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soh, Wee Tee, E-mail: a0046479@u.nus.edu; Ong, C. K.; Peng, Bin

2015-08-15

The spin rectification effect (SRE), a phenomenon that generates dc voltages from ac microwave fields incident onto a conducting ferromagnet, has attracted widespread attention due to its high sensitivity to ferromagnetic resonance (FMR) as well as its relevance to spintronics. Here, we report the non-local detection of yttrium iron garnet (YIG) spin dynamics by measuring SRE voltages from an adjacent conducting NiFe layer up to 200 nm thick. In particular, we detect, within the NiFe layer, SRE voltages stemming from magnetostatic surface spin waves (MSSWs) of the adjacent bulk YIG which are excited by a shorted coaxial probe. These non-localmore » SRE voltages within the NiFe layer that originates from YIG MSSWs are present even in 200 nm-thick NiFe films with a 50 nm thick SiO{sub 2} spacer between NiFe and YIG, thus strongly ruling out the mechanism of spin-pumping induced inverse spin Hall effect in NiFe as the source of these voltages. This long-range influence of YIG dynamics is suggested to be mediated by dynamic fields generated from YIG spin precession near YIG/NiFe interface, which interacts with NiFe spins near the simultaneous resonance of both spins, to generate a non-local SRE voltage within the NiFe layer.« less

Physical processes in high field insulating liquid conduction

NASA Astrophysics Data System (ADS)

Mazarakis, Michael; Kiefer, Mark; Leckbee, Joshua; Anderson, Delmar; Wilkins, Frank; Obregon, Robert

2017-10-01

In the power grid transmission where a large amount of energy is transmitted to long distances, High Voltage DC (HVDC) transmission of up to 1MV becomes more attractive since is more efficient than the counterpart AC. However, two of the most difficult problems to solve are the cable connections to the high voltage power sources and their insulation from the ground. The insulating systems are usually composed of transformer oil and solid insulators. The oil behavior under HVDC is similar to that of a weak electrolyte. Its behavior under HVDC is dominated more by conductivity than dielectric constant. Space charge effects in the oil bulk near high voltage electrodes and impeded plastic insulators affect the voltage oil hold-off. We have constructed an experimental facility where we study the oil and plastic insulator behavior in an actual HVDC System. Experimental results will be presented and compared with the present understanding of the physics governing the oil behavior under very high electrical stresses. Sandia National Laboratories managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. D.O.E., NNSA under contract DE-NA-0003525.

Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air

NASA Astrophysics Data System (ADS)

Zhu, Jiajian; Gao, Jinlong; Li, Zhongshan; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro

2014-12-01

Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating current (AC) power source. The plasma column extended beyond the water-cooled stainless steel electrodes and was stabilized by matching the flow speed of the turbulent air jet with the rated output power. Comprehensive investigations were performed using high-speed movies measured over the plasma column, synchronized with simultaneously recorded current and voltage waveforms. Dynamic details of the novel non-equilibrium discharge are revealed, which is characterized by a sinusoidal current waveform with amplitude stabilized at around 200 mA intermediate between thermal arc and glow discharge, shedding light to the governing mechanism of the sustained spark-suppressed AC gliding arc discharge.

Study of power management technology for orbital multi-100KWe applications. Volume 2: Study results

NASA Technical Reports Server (NTRS)

Mildice, J. W.

1980-01-01

The preliminary requirements and technology advances required for cost effective space power management systems for multi-100 kilowatt requirements were identified. System requirements were defined by establishing a baseline space platform in the 250 KE KWe range and examining typical user loads and interfaces. The most critical design parameters identified for detailed analysis include: increased distribution voltages and space plasma losses, the choice between ac and dc distribution systems, shuttle servicing effects on reliability, life cycle costs, and frequency impacts to power management system and payload systems for AC transmission. The first choice for a power management system for this kind of application and size range is a hybrid ac/dc combination with the following major features: modular design and construction-sized minimum weight/life cycle cost; high voltage transmission (100 Vac RMS); medium voltage array or = 440 Vdc); resonant inversion; transformer rotary joint; high frequency power transmission line or = 20 KHz); energy storage on array side or rotary joint; fully redundant; and 10 year life with minimal replacement and repair.

Performance criteria guideline for three explosion protection methods of electrical equipment rated up to 15,000 volts AC

NASA Technical Reports Server (NTRS)

Linley, L. J.; Luper, A. B.; Dunn, J. H.

1982-01-01

The Bureau of Mines, U.S. Department of the Interior, is reviewing explosion protection methods for use in gassy coal mines. This performance criteria guideline is an evaluation of three explosion protection methods of machines electrically powered with voltages up to 15,000 volts ac. A sufficient amount of basic research has been accomplished to verify that the explosion proof and pressurized enclosure methods can provide adequate explosion protection with the present state of the art up to 15,000 volts ac. This routine application of the potted enclosure as a stand alone protection method requires further investigation or development in order to clarify performance criteria and verification certification requirements. An extensive literature search, a series of high voltage tests, and a design evaluation of the three explosion protection methods indicate that the explosion proof, pressurized, and potted enclosures can all be used to enclose up to 15,000 volts ac.

Experimental investigation on a vectorized aerodynamic dielectric barrier discharge plasma actuator array

NASA Astrophysics Data System (ADS)

Neretti, Gabriele; Cristofolini, Andrea; Borghi, Carlo A.

2014-04-01

The Electro-Hydro-Dynamics (EHD) interaction, induced in atmospheric pressure still air by a surface dielectric barrier discharge (DBD) actuator, had been experimentally studied. A plasma aerodynamic actuator array, able to produce a vectorized jet, with the induced airflow oriented toward the desired direction, had been developed. The array was constituted by a sequence of single surface DBD actuators with kapton as dielectric material. An ac voltage in the range of 0-6 kV peak at 15 kHz had been used. The vectorization had been obtained by feeding the upper electrodes with different voltages and by varying the electrical connections. The lower electrodes had been connected either to ground or to the high voltage source, to produce the desired jet orientation and to avoid plasma formation acting in an undesired direction. Voltage and current measurements had been carried out to evaluate waveforms and to estimate the active power delivered to the discharge. Schlieren imaging allowed to visualize the induced jet and to estimate its orientation. Pitot measurements had been performed to obtain velocity profiles for all jet configurations. A proportional relation between the jet deflection angle and the applied voltage had been found. Moreover, a linear relation had been obtained between the maximum speed in the jet direction and the applied voltage. The active power of the discharge is approximated by both a power law function and an exponential function of the applied voltage.

Gene delivery by microfluidic flow-through electroporation based on constant DC and AC field.

PubMed

Geng, Tao; Zhan, Yihong; Lu, Chang

2012-01-01

Electroporation is one of the most widely used physical methods to deliver exogenous nucleic acids into cells with high efficiency and low toxicity. Conventional electroporation systems typically require expensive pulse generators to provide short electrical pulses at high voltage. In this work, we demonstrate a flow-through electroporation method for continuous transfection of cells based on disposable chips, a syringe pump, and a low-cost power supply that provides a constant voltage. We successfully transfect cells using either DC or AC voltage with high flow rates (ranging from 40 µl/min to 20 ml/min) and high efficiency (up to 75%). We also enable the entire cell membrane to be uniformly permeabilized and dramatically improve gene delivery by inducing complex migrations of cells during the flow.

Theoretical prediction of fast 3D AC electro-osmotic pumps.

PubMed

Bazant, Martin Z; Ben, Yuxing

2006-11-01

AC electro-osmotic (ACEO) pumps in microfluidics currently involve planar electrode arrays, but recent work on the underlying phenomenon of induced-charge electro-osmosis (ICEO) suggests that three-dimensional (3D) geometries may be exploited to achieve faster flows. In this paper, we present some new design principles for periodic 3D ACEO pumps, such as the "fluid conveyor belt" of ICEO flow over a stepped electrode array. Numerical simulations of these designs (using the standard low-voltage model) predict flow rates almost twenty times faster than existing planar ACEO pumps, for the same applied voltage and minimum feature size. These pumps may enable new portable or implantable lab-on-a-chip devices, since rather fast (mm s(-1)), tuneable flows should be attainable with battery voltages (<10 V).

Current source density analysis of the hippocampal theta rhythm: associated sustained potentials and candidate synaptic generators.

PubMed

Brankack, J; Stewart, M; Fox, S E

1993-07-02

Single-electrode depth profiles of the hippocampal EEG were made in urethane-anesthetized rats and rats trained in an alternating running/drinking task. Current source density (CSD) was computed from the voltage as a function of depth. A problem inherent to AC-coupled profiles was eliminated by incorporating sustained potential components of the EEG. 'AC' profiles force phasic current sinks to alternate with current sources at each lamina, changing the magnitude and even the sign of the computed membrane current. It was possible to include DC potentials in the profiles from anesthetized rats by using glass micropipettes for recording. A method of 'subtracting' profiles of the non-theta EEG from theta profiles was developed as an approach to including sustained potentials in recordings from freely-moving animals implanted with platinum electrodes. 'DC' profiles are superior to 'AC' profiles for analysis of EEG activity because 'DC'-CSD values can be considered correct in sign and more closely represent the actual membrane current magnitudes. Since hippocampal inputs are laminated, CSD analysis leads to straightforward predictions of the afferents involved. Theta-related activity in afferents from entorhinal neurons, hippocampal interneurons and ipsi- and contralateral hippocampal pyramids all appear to contribute to sources and sinks in CA1 and the dentate area. The largest theta-related generator was a sink at the fissure, having both phasic and tonic components. This sink may reflect activity in afferents from the lateral entorhinal cortex. The phase of the dentate mid-molecular sink suggests that medial entorhinal afferents drive the theta-related granule and pyramidal cell firing. The sustained components may be simply due to different average rates of firing during theta rhythm than during non-theta EEG in afferents whose firing rates are also phasically modulated.

Steady-state and dynamic characteristics of a 20-kHz spacecraft power system - Control of harmonic resonance

NASA Technical Reports Server (NTRS)

Wasynczuk, O.; Krause, P. C.; Biess, J. J.; Kapustka, R.

1990-01-01

A detailed computer simulation was used to illustrate the steady-state and dynamic operating characteristics of a 20-kHz resonant spacecraft power system. The simulated system consists of a parallel-connected set of DC-inductor resonant inverters (drivers), a 440-V cable, a node transformer, a 220-V cable, and a transformer-rectifier-filter (TRF) AC-to-DC receiver load. Also included in the system are a 1-kW 0.8-pf RL load and a double-LC filter connected at the receiving end of the 20-kHz AC system. The detailed computer simulation was used to illustrate the normal steady-state operating characteristics and the dynamic system performance following, for example, TRF startup. It is shown that without any filtering the given system exhibits harmonic resonances due to an interaction between the switching of the source and/or load converters and the AC system. However, the double-LC filter at the receiving-end of the AC system and harmonic traps connected in series with each of the drivers significantly reduce the harmonic distortion of the 20-kHz bus voltage. Significant additional improvement in the waveform quality can be achieved by including a double-LC filter with each driver.

A Discrete-Time Average Model Based Predictive Control for Quasi-Z-Source Inverter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yushan; Abu-Rub, Haitham; Xue, Yaosuo

A discrete-time average model-based predictive control (DTA-MPC) is proposed for a quasi-Z-source inverter (qZSI). As a single-stage inverter topology, the qZSI regulates the dc-link voltage and the ac output voltage through the shoot-through (ST) duty cycle and the modulation index. Several feedback strategies have been dedicated to produce these two control variables, among which the most popular are the proportional–integral (PI)-based control and the conventional model-predictive control (MPC). However, in the former, there are tradeoffs between fast response and stability; the latter is robust, but at the cost of high calculation burden and variable switching frequency. Moreover, they require anmore » elaborated design or fine tuning of controller parameters. The proposed DTA-MPC predicts future behaviors of the ST duty cycle and modulation signals, based on the established discrete-time average model of the quasi-Z-source (qZS) inductor current, the qZS capacitor voltage, and load currents. The prediction actions are applied to the qZSI modulator in the next sampling instant, without the need of other controller parameters’ design. A constant switching frequency and significantly reduced computations are achieved with high performance. Transient responses and steady-state accuracy of the qZSI system under the proposed DTA-MPC are investigated and compared with the PI-based control and the conventional MPC. Simulation and experimental results verify the effectiveness of the proposed approach for the qZSI.« less

A Discrete-Time Average Model Based Predictive Control for Quasi-Z-Source Inverter

DOE PAGES

Liu, Yushan; Abu-Rub, Haitham; Xue, Yaosuo; ...

2017-12-25

A discrete-time average model-based predictive control (DTA-MPC) is proposed for a quasi-Z-source inverter (qZSI). As a single-stage inverter topology, the qZSI regulates the dc-link voltage and the ac output voltage through the shoot-through (ST) duty cycle and the modulation index. Several feedback strategies have been dedicated to produce these two control variables, among which the most popular are the proportional–integral (PI)-based control and the conventional model-predictive control (MPC). However, in the former, there are tradeoffs between fast response and stability; the latter is robust, but at the cost of high calculation burden and variable switching frequency. Moreover, they require anmore » elaborated design or fine tuning of controller parameters. The proposed DTA-MPC predicts future behaviors of the ST duty cycle and modulation signals, based on the established discrete-time average model of the quasi-Z-source (qZS) inductor current, the qZS capacitor voltage, and load currents. The prediction actions are applied to the qZSI modulator in the next sampling instant, without the need of other controller parameters’ design. A constant switching frequency and significantly reduced computations are achieved with high performance. Transient responses and steady-state accuracy of the qZSI system under the proposed DTA-MPC are investigated and compared with the PI-based control and the conventional MPC. Simulation and experimental results verify the effectiveness of the proposed approach for the qZSI.« less

Alternating current breakdown voltage of ice electret

NASA Astrophysics Data System (ADS)

Oshika, Y.; Tsuchiya, Y.; Okumura, T.; Muramoto, Y.

2017-09-01

Ice has low environmental impact. Our research objectives are to study the availability of ice as a dielectric insulating material at cryogenic temperatures. We focus on ferroelectric ice (iceXI) at cryogenic temperatures. The properties of iceXI, including its formation, are not clear. We attempted to obtain the polarized ice that was similar to iceXI under the applied voltage and cooling to 77 K. The polarized ice have a wide range of engineering applications as electronic materials at cryogenic temperatures. This polarized ice is called ice electret. The structural difference between ice electret and normal ice is only the positions of protons. The effects of the proton arrangement on the breakdown voltage of ice electret were shown because electrical properties are influenced by the structure of ice. We observed an alternating current (ac) breakdown voltage of ice electret and normal ice at 77 K. The mean and minimum ac breakdown voltage values of ice electret were higher than those of normal ice. We considered that the electrically weak part of the normal ice was improved by applied a direct electric field.

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

DOEpatents

Vail, III, William Banning; Momii, Steven Thomas

2001-01-01

A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

DOEpatents

Vail III, William Banning; Momii, Steven Thomas

2003-06-10

A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

CFAVC scheme for high frequency series resonant inverter-fed domestic induction heating system

NASA Astrophysics Data System (ADS)

Nagarajan, Booma; Reddy Sathi, Rama

2016-01-01

This article presents the investigations on the constant frequency asymmetric voltage cancellation control in the AC-AC resonant converter-fed domestic induction heating system. Conventional fixed frequency control techniques used in the high frequency converters lead to non-zero voltage switching operation and reduced output power. The proposed control technique produces higher output power than the conventional fixed-frequency control strategies. In this control technique, zero-voltage-switching operation is maintained during different duty cycle operation for reduction in the switching losses. Complete analysis of the induction heating power supply system with asymmetric voltage cancellation control is discussed in this article. Simulation and experimental study on constant frequency asymmetric voltage cancellation (CFAVC)-controlled full bridge series resonant inverter is performed. Time domain simulation results for the open and closed loop of the system are obtained using MATLAB simulation tool. The simulation results prove the control of voltage and power in a wide range. PID controller-based closed loop control system achieves the voltage regulation of the proposed system for the step change in load. Hardware implementation of the system under CFAVC control is done using the embedded controller. The simulation and experimental results validate the performance of the CFAVC control technique for series resonant-based induction cooking system.

Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits

DOEpatents

Campbell, Ann. N.; Anderson, Richard E.; Cole, Jr., Edward I.

1995-01-01

A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits.

Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits

DOEpatents

Campbell, A.N.; Anderson, R.E.; Cole, E.I. Jr.

1995-11-07

A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits are disclosed. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits. 17 figs.

Method for making glass nonfogging

DOEpatents

Lord, David E.; Carter, Gary W.; Petrini, Richard R.

1979-01-01

A method for rendering glass nonfogging (to condensation fog) by sandwiching the glass between two electrodes such that the glass functions as the dielectric of a capacitor, a large alternating current (AC) voltage is applied across the electrodes for a selected time period causing the glass to absorb a charge, and the electrodes are removed. The glass absorbs a charge from the electrodes rendering it nonfogging. The glass surface is undamaged by application of the AC voltage, and normal optical properties are unaffected. This method can be applied to optical surfaces such as lenses, auto windshields, mirrors, etc., wherever condensation fog on glass is a problem.

Quantitative study of electrophoretic and electroosmotic enhancement during alternating current iontophoresis across synthetic membranes.

PubMed

Yan, Guang; Li, S Kevin; Peck, Kendall D; Zhu, Honggang; Higuchi, William I

2004-12-01

One of the primary safety and tolerability limitations of direct current iontophoresis is the potential for electrochemical burns associated with the necessary current densities and/or application times required for effective treatment. Alternating current (AC) transdermal iontophoresis has the potential to eliminate electrochemical burns that are frequently observed during direct current transdermal iontophoresis. Although it has been demonstrated that the intrinsic permeability of skin can be increased by applying low-to-moderate AC voltages, transdermal transport phenomena and enhancement under AC conditions have not been systematically studied and are not well understood. The aim of the present work was to study the fundamental transport mechanisms of square-wave AC iontophoresis using a synthetic membrane system. The model synthetic membrane used was a composite Nuclepore membrane. AC frequencies ranging from 20 to 1000 Hz and AC fields ranging from 0.25 to 0.5 V/membrane were investigated. A charged permeant, tetraethyl ammonium, and a neutral permeant, arabinose, were used. The transport studies showed that flux was enhanced by increasing the AC voltage and decreasing AC frequency. Two theoretical transport models were developed: one is a homogeneous membrane model; the other is a heterogeneous membrane model. Experimental transport data were compared with computer simulations based on these models. Excellent agreement between model predictions and experimental data was observed when the data were compared with the simulations from the heterogeneous membrane model. (c) 2004 Wiley-Liss, Inc. and the American Pharmacists Association

ac electroosmotic pumping induced by noncontact external electrodes.

PubMed

Wang, Shau-Chun; Chen, Hsiao-Ping; Chang, Hsueh-Chia

2007-09-21

Electroosmotic (EO) pumps based on dc electroosmosis is plagued by bubble generation and other electrochemical reactions at the electrodes at voltages beyond 1 V for electrolytes. These disadvantages limit their throughput and offset their portability advantage over mechanical syringe or pneumatic pumps. ac electroosmotic pumps at high frequency (>100 kHz) circumvent the bubble problem by inducing polarization and slip velocity on embedded electrodes,1 but they require complex electrode designs to produce a net flow. We report a new high-throughput ac EO pump design based on induced-polarization on the entire channel surface instead of just on the electrodes. Like dc EO pumps, our pump electrodes are outside of the load section and form a cm-long pump unit consisting of three circular reservoirs (3 mm in diameter) connected by a 1x1 mm channel. The field-induced polarization can produce an effective Zeta potential exceeding 1 V and an ac slip velocity estimated as 1 mmsec or higher, both one order of magnitude higher than earlier dc and ac pumps, giving rise to a maximum throughput of 1 mulsec. Polarization over the entire channel surface, quadratic scaling with respect to the field and high voltage at high frequency without electrode bubble generation are the reasons why the current pump is superior to earlier dc and ac EO pumps.

Two-Stage Series-Resonant Inverter

NASA Technical Reports Server (NTRS)

Stuart, Thomas A.

1994-01-01

Two-stage inverter includes variable-frequency, voltage-regulating first stage and fixed-frequency second stage. Lightweight circuit provides regulated power and is invulnerable to output short circuits. Does not require large capacitor across ac bus, like parallel resonant designs. Particularly suitable for use in ac-power-distribution system of aircraft.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter.

PubMed

Gottardi, L; Adams, J; Bailey, C; Bandler, S; Bruijn, M; Chervenak, J; Eckart, M; Finkbeiner, F; den Hartog, R; Hoevers, H; Kelley, R; Kilbourne, C; de Korte, P; van der Kuur, J; Lindeman, M; Porter, F; Sadlier, J; Smith, S

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Δ E FWHM =3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterised the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

Efficiency estimation method of three-wired AC to DC line transfer

NASA Astrophysics Data System (ADS)

Solovev, S. V.; Bardanov, A. I.

2018-05-01

The development of power semiconductor converters technology expands the scope of their application to medium voltage distribution networks (6-35 kV). Particularly rectifiers and inverters of appropriate power capacity complement the topology of such voltage level networks with the DC links and lines. The article presents a coefficient that allows taking into account the increase of transmission line capacity depending on the parameters of it. The application of the coefficient is presented by the example of transfer three-wired AC line to DC in various methods. Dependences of the change in the capacity from the load power factor of the line and the reactive component of the resistance of the transmission line are obtained. Conclusions are drawn about the most efficient ways of converting a three-wired AC line to direct current.

Small-Signal Dynamic Analysis of LCC-HVDC with STATCOM at the Inverter Busbar

NASA Astrophysics Data System (ADS)

Liu, Dong; Jiang, Wen; Guo, Chunyi; Rehman, Atiq Ur; Zhao, Chengyong

2018-01-01

This paper develops a linearized small-signal dynamic model of a Line-Commutated-Converter based HVDC (LCC-HVDC) system with STATCOM at the inverter busbar, and validates its accuracy by comparing time-domain responses from small-signal model and PSCAD-based simulation results. Considering the potential impact of Phase-Locked-Loop (PLL) parameters on the study system and the close connection of STATCOM and LCC inverter station at AC busbar, this paper investigates the impact of PLL gains and AC voltage control parameters of STATCOM on the system small-signal stability. The studies show that (i) the PLL gain has highly impact on the study system and smaller PLL gains are preferable; (ii) larger values of both the proportional gain and the integral gain of AC voltage controller of STATCOM could result in oscillation/instability of the system.

Electrochemical performance of microporous and mesoporous activated carbons in neat and diluted 1-ethyl-3-methylimidazolium tetrafluoroborate

NASA Astrophysics Data System (ADS)

Kumagai, Seiji; Hatomi, Masaki; Tashima, Daisuke

2017-03-01

1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIm·BF4), neat and diluted with propylene carbonate to 1 mol L-1, have been employed as electrolytes of electrical double-layer capacitors (EDLCs). The effects of microporosity and mesoporosity in activated carbon (AC) electrodes on the capacitive and resistive performances upon the use of neat and diluted EMIm·BF4 have been explored. In addition to cyclic voltammetry and galvanostatic charge-discharge tests, electrochemical impedance spectroscopy has been performed employing Kang's equivalent circuit model consisting of three resistances, three constant phase elements, and one bounded Warburg impedance. The overall impedance of the EDLC cell was separated into components of intrinsic resistance, bulk electrolyte, diffusion layer, and Helmholtz layer. The specific capacitance and the equivalent series resistance (ESR) of mesoporous AC were found to be highly dependent on the rate of ionic transfer. Lower cell voltage was identified as being responsible for lower specific capacitance and larger ESR of mesoporous AC, which was similarly seen in the neat and diluted EMIm·BF4, and could be alleviated by increasing the cell voltage. The inferior rate performance and the cell-voltage-dependent performance of mesoporous AC, which were more distinctly observed in the neat EMIm·BF4, could be attributed to the lower mobility of EMIm+ and BF4- in mesopores.

Fundamental Understanding of the Impact High Pulsed Power Loading has on a MicroGrid’s DC or AC Bus

DTIC Science & Technology

2013-06-12

The lithium - ion battery module is made up of two parallel stacks of six 4.1 V GALA 27 Ah cells providing a 54 Ah, 24.4 V source voltage with a -3.0...100 Ah Gel cell lead-acid (left) and 54 Ah GALA lithium - ion battery (right) energy storage modules. During each experiment, the output of the buck...batteries are used. Because the lithium - ion battery ESR is lower than that of the lead-acid, it contributes more to the rise time of the discharge

Capaciflector-guided mechanisms

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

1996-01-01

A plurality of capaciflector proximity sensors, one or more of which may be overlaid on each other, and at least one shield are mounted on a device guided by a robot so as to see a designated surface, hole or raised portion of an object, for example, in three dimensions. Individual current-measuring voltage follower circuits interface the sensors and shield to a common AC signal source. As the device approaches the object, the sensors respond by a change in the currents therethrough. The currents are detected by the respective current-measuring voltage follower circuits with the outputs thereof being fed to a robot controller. The device is caused to move under robot control in a predetermined pattern over the object while directly referencing each other without any offsets, whereupon by a process of minimization of the sensed currents, the device is dithered or wiggled into position for a soft touchdown or contact without any prior contact with the object.

Torque ripple reduction of brushless DC motor based on adaptive input-output feedback linearization.

PubMed

Shirvani Boroujeni, M; Markadeh, G R Arab; Soltani, J

2017-09-01

Torque ripple reduction of Brushless DC Motors (BLDCs) is an interesting subject in variable speed AC drives. In this paper at first, a mathematical expression for torque ripple harmonics is obtained. Then for a non-ideal BLDC motor with known harmonic contents of back-EMF, calculation of desired reference current amplitudes, which are required to eliminate some selected harmonics of torque ripple, are reviewed. In order to inject the reference harmonic currents to the motor windings, an Adaptive Input-Output Feedback Linearization (AIOFBL) control is proposed, which generates the reference voltages for three phases voltage source inverter in stationary reference frame. Experimental results are presented to show the capability and validity of the proposed control method and are compared with the vector control in Multi-Reference Frame (MRF) and Pseudo-Vector Control (P-VC) method results. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

An isolated bridgeless AC-DC PFC converter using a LC resonant voltage doubler rectifier

NASA Astrophysics Data System (ADS)

Lee, Sin-woo; Do, Hyun-Lark

2016-12-01

This paper proposed an isolated bridgeless AC-DC power factor correction (PFC) converter using a LC resonant voltage doubler rectifier. The proposed converter is based on isolated conventional single-ended primary inductance converter (SEPIC) PFC converter. The conduction loss of rectification is reduced than a conventional one because the proposed converter is designed to eliminate a full-bridge rectifier at an input stage. Moreover, for zero-current switching (ZCS) operation and low voltage stresses of output diodes, the secondary of the proposed converter is designed as voltage doubler with a LC resonant tank. Additionally, an input-output electrical isolation is provided for safety standard. In conclusion, high power factor is achieved and efficiency is improved. The operational principles, steady-state analysis and design equations of the proposed converter are described in detail. Experimental results from a 60 W prototype at a constant switching frequency 100 kHz are presented to verify the performance of the proposed converter.

Lamp for generating high power ultraviolet radiation

DOEpatents

Morgan, Gary L.; Potter, James M.

2001-01-01

The apparatus is a gas filled ultraviolet generating lamp for use as a liquid purifier. The lamp is powred by high voltage AC, but has no metallic electrodes within or in contact with the gas enclosure which is constructed as two concentric quartz cylinders sealed together at their ends with the gas fill between the cylinders. Cooling liquid is pumped through the volume inside the inner quartz cylinder where an electrically conductive pipe spaced from the inner cylinder is used to supply the cooling liquid and act as the high voltage electrode. The gas enclosure is enclosed within but spaced from a metal housing which is connected to operate as the ground electrode of the circuit and through which the treated fluid flows. Thus, the electrical circuit is from the central pipe, and through the cooling liquid, the gas enclosure, the treated liquid on the outside of the outer quartz cylinder, and to the housing. The high voltage electrode is electrically isolated from the source of cooling liquid by a length of insulated hose which also supplies the cooling liquid.

AC and DC electrical behavior of MWCNT/epoxy nanocomposite near percolation threshold: Equivalent circuits and percolation limits

NASA Astrophysics Data System (ADS)

Alizadeh Sahraei, Abolfazl; Ayati, Moosa; Baniassadi, Majid; Rodrigue, Denis; Baghani, Mostafa; Abdi, Yaser

2018-03-01

This study attempts to comprehensively investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the AC and DC electrical conductivity of epoxy nanocomposites. The samples (0.2, 0.3, and 0.5 wt. % MWCNT) were produced using a combination of ultrason and shear mixing methods. DC measurements were performed by continuous measurement of the current-voltage response and the results were analyzed via a numerical percolation approach, while for the AC behavior, the frequency response was studied by analyzing phase difference and impedance in the 10 Hz to 0.2 MHz frequency range. The results showed that the dielectric parameters, including relative permittivity, impedance phase, and magnitude, present completely different behaviors for the frequency range and MWCNT weight fractions studied. To better understand the nanocomposites electrical behavior, equivalent electric circuits were also built for both DC and AC modes. The DC equivalent networks were developed based on the current-voltage curves, while the AC equivalent circuits were proposed by using an optimization problem according to the impedance magnitude and phase at different frequencies. The obtained equivalent electrical circuits were found to be highly useful tools to understand the physical mechanisms involved in MWCNT filled polymer nanocomposites.

Power Factor Controller

NASA Technical Reports Server (NTRS)

1997-01-01

Frank Nola invented the Power Factor Controller (PFC) at Marshall Space Flight Center more than a decade ago. Nola came up with a way to curb power wastage in AC induction motors. The PFC matches voltage with the motor's actual need by continuously sensing shifts between voltage and current. When it senses a light load it cuts the voltage to the minimum needed. Potential energy savings range from 8 to 65 percent.

Benefit from NASA

NASA Image and Video Library

1997-01-01

Frank Nola invented the Power Factor Controller (PFC) at Marshall Space Flight Center more than a decade ago. Nola came up with a way to curb power wastage in AC induction motors. The PFC matches voltage with the motor's actual need by continuously sensing shifts between voltage and current. When it senses a light load it cuts the voltage to the minimum needed. Potential energy savings range from 8 to 65 percent.

A novel power converter for photovoltaic applications

NASA Astrophysics Data System (ADS)

Yuvarajan, S.; Yu, Dachuan; Xu, Shanguang

A simple and economical power conditioner to convert the power available from solar panels into 60 Hz ac voltage is described. The raw dc voltage from the solar panels is converted to a regulated dc voltage using a boost converter and a large capacitor and the dc output is then converted to 60 Hz ac using a bridge inverter. The ratio between the load current and the short-circuit current of a PV panel at maximum power point is nearly constant for different insolation (light) levels and this property is utilized in designing a simple maximum power point tracking (MPPT) controller. The controller includes a novel arrangement for sensing the short-circuit current without disturbing the operation of the PV panel and implementing MPPT. The switching losses in the inverter are reduced by using snubbers. The results obtained on an experimental converter are presented.

Reversible Control of Anisotropic Electrical Conductivity using Colloidal Microfluidic Networks

DTIC Science & Technology

2007-04-17

field with the induced charges on each electrode result in AC electroosmotic force and steady fluid flow (nonzero time averaged) with a velocity...direction of the AC electroosmotic force (flow is unidirectional). From the work of Green and co- workers, we can write the particle displacement due to... AC voltage-frequency phase space allows us to probe a wide range of colloidal configurations that resemble “capacitive” and “resistive” networks in

Two new families of high-gain dc-dc power electronic converters for dc-microgrids

NASA Astrophysics Data System (ADS)

Prabhala, Venkata Anand Kishore

Distributing the electric power in dc form is an appealing solution in many applications such as telecommunications, data centers, commercial buildings, and microgrids. A high gain dc-dc power electronic converter can be used to individually link low-voltage elements such as solar panels, fuel cells, and batteries to the dc voltage bus which is usually 400 volts. This way, it is not required to put such elements in a series string to build up their voltages. Consequently, each element can function at it optimal operating point regardless of the other elements in the system. In this dissertation, first a comparative study of dc microgrid architectures and their advantages over their ac counterparts is presented. Voltage level selection of dc distribution systems is discussed from the cost, reliability, efficiency, and safety standpoints. Next, a new family of non-isolated high-voltage-gain dc-dc power electronic converters with unidirectional power flow is introduced. This family of converters benefits from a low voltage stress across its switches. The proposed topologies are versatile as they can be utilized as single-input or double-input power converters. In either case, they draw continuous currents from their sources. Lastly, a bidirectional high-voltage-gain dc-dc power electronic converter is proposed. This converter is comprised of a bidirectional boost converter which feeds a switched-capacitor architecture. The switched-capacitor stage suggested here has several advantages over the existing approaches. For example, it benefits from a higher voltage gain while it uses less number of capacitors. The proposed converters are highly efficient and modular. The operating modes, dc voltage gain, and design procedure for each converter are discussed in details. Hardware prototypes have been developed in the lab. The results obtained from the hardware agree with those of the simulation models.

High Voltage Hybrid Electric Propulsion - Multilayered Functional Insulation System (MFIS) NASA-GRC

NASA Technical Reports Server (NTRS)

Lizcano, M.

2017-01-01

High power transmission cables pose a key challenge in future Hybrid Electric Propulsion Aircraft. The challenge arises in developing safe transmission lines that can withstand the unique environment found in aircraft while providing megawatts of power. High voltage AC, variable frequency cables do not currently exist and present particular electrical insulation challenges since electrical arcing and high heating are more prevalent at higher voltages and frequencies. Identifying and developing materials that maintain their dielectric properties at high voltage and frequencies is crucial.

Megawatt Space Power Conditioning, Distribution, and Control Study

DTIC Science & Technology

1988-03-01

also must be given to the design of an ac transmission line for this relatively high frequency . 2.3.2 Medium High Voltage Systems. Figure 2-4 shows a...systems are designed to exploit the use of 2 MW klystrode tubes (see Section 3.1) which require a dc voltage of about 140 kV. This high voltage can be...the concerns is that to date there have been no three-phase high voltage, high frequency transmission lines designed . Figure 5-6. While the previous

Electrical safety for high voltage arrays

NASA Technical Reports Server (NTRS)

Marshall, N. A.

1983-01-01

A number of key electrical safety requirements for the high voltage arrays of central station photovoltaic power systems are explored. The suitability of representative industrial DC power switchgear for control and fault protection was evaluated. Included were AC/DC circuit breakers, electromechanical contactors and relays, load interruptors, cold disconnect devices, sectionalizing switches, and high voltage DC fuses. As appropriate, steady state and transient characteristics were analyzed. Failure modes impacting upon operation and maintenance safety were also identified, as were the voltage withstand and current interruption levels.

Description of a 20 kilohertz power distribution system

NASA Technical Reports Server (NTRS)

Hansen, I. G.

1986-01-01

A single phase, 440 VRMS, 20 kHz power distribution system with a regulated sinusoidal wave form is discussed. A single phase power system minimizes the wiring, sensing, and control complexities required in a multi-sourced redundantly distributed power system. The single phase addresses only the distribution links multiphase lower frequency inputs and outputs accommodation techniques are described. While the 440 V operating potential was initially selected for aircraft operating below 50,000 ft, this potential also appears suitable for space power systems. This voltage choice recognizes a reasonable upper limit for semiconductor ratings, yet will direct synthesis of 220 V, 3 power. A 20 kHz operating frequency was selected to be above the range of audibility, minimize the weight of reactive components, yet allow the construction of single power stages of 25 to 30 kW. The regulated sinusoidal distribution system has several advantages. With a regulated voltage, most ac/dc conversions involve rather simple transformer rectifier applications. A sinusoidal distribution system, when used in conjunction with zero crossing switching, represents a minimal source of EMI. The present state of 20 kHz power technology includes computer controls of voltage and/or frequency, low inductance cable, current limiting circuit protection, bi-directional power flow, and motor/generator operating using standard induction machines. A status update and description of each of these items and their significance is presented.

Description of a 20 Kilohertz power distribution system

NASA Technical Reports Server (NTRS)

Hansen, I. G.

1986-01-01

A single phase, 440 VRMS, 20 kHz power distribution system with a regulated sinusoidal wave form is discussed. A single phase power system minimizes the wiring, sensing, and control complexities required in a multi-sourced redundantly distributed power system. The single phase addresses only the distribution link; mulitphase lower frequency inputs and outputs accommodation techniques are described. While the 440 V operating potential was initially selected for aircraft operating below 50,000 ft, this potential also appears suitable for space power systems. This voltage choice recognizes a reasonable upper limit for semiconductor ratings, yet will direct synthesis of 220 V, 3 power. A 20 kHz operating frequency was selected to be above the range of audibility, minimize the weight of reactive components, yet allow the construction of single power stages of 25 to 30 kW. The regulated sinusoidal distribution system has several advantages. With a regulated voltage, most ac/dc conversions involve rather simple transformer rectifier applications. A sinusoidal distribution system, when used in conjunction with zero crossing switching, represents a minimal source of EMI. The present state of 20 kHz power technology includes computer controls of voltage and/or frequency, low inductance cable, current limiting circuit protection, bi-directional power flow, and motor/generator operating using standard induction machines. A status update and description of each of these items and their significance is presented.

Properties and Applications of Varistor-Transistor Hybrid Devices

NASA Astrophysics Data System (ADS)

Pandey, R. K.; Stapleton, William A.; Sutanto, Ivan; Scantlin, Amanda A.; Lin, Sidney

2014-05-01

The nonlinear current-voltage characteristics of a varistor device are modified with the help of external agents, resulting in tuned varistor-transistor hybrid devices with multiple applications. The substrate used to produce these hybrid devices belongs to the modified iron titanate family with chemical formula 0.55FeTiO3·0.45Fe2O3 (IHC45), which is a prominent member of the ilmenite-hematite solid-solution series. It is a wide-bandgap magnetic oxide semiconductor. Electrical resistivity and Seebeck coefficient measurements from room temperature to about 700°C confirm that it retains its p-type nature for the entire temperature range. The direct-current (DC) and alternating-current (AC) properties of these hybrid devices are discussed and their applications identified. It is shown here that such varistor embedded ceramic transistors with many interesting properties and applications can be mass produced using incredibly simple structures. The tuned varistors by themselves can be used for current amplification and band-pass filters. The transistors on the other hand could be used to produce sensors, voltage-controlled current sources, current-controlled voltage sources, signal amplifiers, and low-band-pass filters. We believe that these devices could be suitable for a number of applications in consumer and defense electronics, high-temperature and space electronics, bioelectronics, and possibly also for electronics specific to handheld devices.

Ring magnet firing angle control

DOEpatents

Knott, M.J.; Lewis, L.G.; Rabe, H.H.

1975-10-21

A device is provided for controlling the firing angles of thyratrons (rectifiers) in a ring magnet power supply. A phase lock loop develops a smooth ac signal of frequency equal to and in phase with the frequency of the voltage wave developed by the main generator of the power supply. A counter that counts from zero to a particular number each cycle of the main generator voltage wave is synchronized with the smooth AC signal of the phase lock loop. Gates compare the number in the counter with predetermined desired firing angles for each thyratron and with coincidence the proper thyratron is fired at the predetermined firing angle.

Ripple feedback for the resonant-filter unity-power-factor rectifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Streng, S.A.; King, R.J.

1992-07-01

An unusual bucklike unity-power-factor rectifier with a resonant load-balancing network permits current-limited operation down to zero output voltage in a single-stage-topology. However, this rectifier has been found to be sensitive to ac-line voltage distortion and is potentially unstable with realistic values of ac-line impedance. In this paper, a new ripple feedback is proposed that solves both problems. A large-signal time-varying analysis is given along with incremental, quasi-static, and low-frequency approximations. Experimental verification is provided by a 500-W 50-kHz rectifier operating from the 120-V 60-Hz distribution system.

Experimental and theoretical characterization of an AC electroosmotic micromixer.

PubMed

Sasaki, Naoki; Kitamori, Takehiko; Kim, Haeng-Boo

2010-01-01

We have reported on a novel microfluidic mixer based on AC electroosmosis. To elucidate the mixer characteristics, we performed detailed measurements of mixing under various experimental conditions including applied voltage, frequency and solution viscosity. The results are discussed through comparison with results obtained from a theoretical model of AC electroosmosis. As predicted from the theoretical model, we found that a larger voltage (approximately 20 V(p-p)) led to more rapid mixing, while the dependence of the mixing on frequency (1-5 kHz) was insignificant under the present experimental conditions. Furthermore, the dependence of the mixing on viscosity was successfully explained by the theoretical model, and the applicability of the mixer in viscous solution (2.83 mPa s) was confirmed experimentally. By using these results, it is possible to estimate the mixing performance under given conditions. These estimations can provide guidelines for using the mixer in microfluidic chemical analysis.

A new bed-exiting alarm system for welfare facility residents.

PubMed

Ogawa, Hidekuni; Yonezawa, Yoshiharu; Maki, Hiromichi; Caldwell, W

2009-01-01

A newly developed alarm system detects welfare facility residents leaving their beds, and does not respond to the care staff, who wear shoes or slippers. It employs a stainless steel tape electrode, several linear integrated circuits and a low-power 8-bit single chip microcomputer. The electrode, which is used as a bed-exiting detection sensor, is attached to the floor mat to record changes in the always-present AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the standard 100 volt, 60 Hz AC utility power wiring in the room walls and ceiling. The resident's body movements, before trying to get out of bed and after leaving the bed, are detected by the microcomputer from changes in the induced AC voltage. The microcomputer alerts the care staff station, via a power line communication system or PHS (personal handy phone System).

Performance of Natural Dye and Counter Electrode from Robusta Coffee Beans Peel Waste for Fabrication of Dye-Sensitized Solar Cell (DSSC)

NASA Astrophysics Data System (ADS)

Setiawan, T.; Subekti, W. Y.; Nur'Adya, S. S.; Ilmiah, K.; Ulfa, S. M.

2018-01-01

The DSSC prototype using activated carbon (AC) and natural dye from Robusta coffee bean peels have been investigated. The natural dye obtained from the extraction of Robusta coffee bean peels is identified as anthocyanin by UV-Vis spectrophotometer at maximum wavelength 219.5 nm and 720.0 nm in methanol. From the FT-IR analysis, the vibration of O-H observed at 3385 cm-1, C=O at 1618 cm-1, and C-O-C at 1065 cm-1. The counter electrode prepared by calcined the peels at 300°C. Surface analyser of AC showed the larger surface area compared prior activation. The DSSC prototype was prepared using FTO glass (2x2 cm) coated with carbon paste in various thickness. The working electrode is coated with the TiO2 paste. The optimum voltage measured was 395mV (300 μL of CA), 334 mV (200 μL AC), and 254 mV (100 μL AC). From this result, we understand that the thickness of counter electrode influent the voltage of the DSSC.

Performance of an X-ray single pixel TES microcalorimeter under DC and AC biasing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gottardi, L.; Kuur, J. van der; Korte, P. A. J. de

2009-12-16

We are developing Frequency Domain Multiplexing (FDM) for the read-out of TES imaging microcalorimeter arrays for future X-ray missions like IXO. In the FDM configuration the TES is AC voltage biased at a well defined frequencies (between 0.3 to 10 MHz) and acts as an AM modulating element. In this paper we will present a full comparison of the performance of a TES microcalorimeter under DC bias and AC bias at a frequency of 370 kHz. In both cases we measured the current-to-voltage characteristics, the complex impedance, the noise, the X-ray responsivity, and energy resolution. The behaviour is very similarmore » in both cases, but deviations in performances are observed for detector working points low in the superconducting transition (R/R{sub N}<0.5). The measured energy resolution at 5.89 keV is 2.7 eV for DC bias and 3.7 eV for AC bias, while the baseline resolution is 2.8 eV and 3.3 eV, respectively.« less

A Hybrid LCC-VSC HVDC Transmission System Supplying a Passive Load

NASA Astrophysics Data System (ADS)

Kotb, Omar

High Voltage Direct Current (HVDC) transmission systems continue to be an excellent asset in modern power systems, mainly for their ability to overcome the problems of AC transmission, such as the interconnection of asynchronous grids, stability of long transmission lines, and use of long cables for power transmission. In the past 20 years, Voltage Source Converter (VSC)-HVDC transmission systems were developed and installed in many projects, thereby adding more operational benefits to DC transmission option, such as high controllability, ability to supply weak networks, and reduced converter reactive power demand. Nevertheless, VSC-HVDC transmission suffers from the disadvantages of high losses and cost. In this research, a hybrid HVDC employing a Line Commutated Converter (LCC) as rectifier and a VSC as inverter is used to supply a passive network through a DC cable. The hybrid system is best suited for unidirectional power transmission scenarios, such as power transmission to islands and remote load centers, where the construction of new transmission lines is prohibitively expensive. Control modes for the rectifier and inverter are selected and implemented using Proportional Integral (PI) controllers. Special control schemes are developed for abnormal operating conditions such as starting at light load and recovering from AC network faults. The system performance under steady state and transient conditions is investigated by EMTP-RV simulations. The results show the feasibility of the hybrid system.

ac electroosmotic pumping induced by noncontact external electrodes

PubMed Central

Wang, Shau-Chun; Chen, Hsiao-Ping; Chang, Hsueh-Chia

2007-01-01

Electroosmotic (EO) pumps based on dc electroosmosis is plagued by bubble generation and other electrochemical reactions at the electrodes at voltages beyond 1 V for electrolytes. These disadvantages limit their throughput and offset their portability advantage over mechanical syringe or pneumatic pumps. ac electroosmotic pumps at high frequency (>100 kHz) circumvent the bubble problem by inducing polarization and slip velocity on embedded electrodes,1 but they require complex electrode designs to produce a net flow. We report a new high-throughput ac EO pump design based on induced-polarization on the entire channel surface instead of just on the electrodes. Like dc EO pumps, our pump electrodes are outside of the load section and form a cm-long pump unit consisting of three circular reservoirs (3 mm in diameter) connected by a 1×1 mm channel. The field-induced polarization can produce an effective Zeta potential exceeding 1 V and an ac slip velocity estimated as 1 mm∕sec or higher, both one order of magnitude higher than earlier dc and ac pumps, giving rise to a maximum throughput of 1 μl∕sec. Polarization over the entire channel surface, quadratic scaling with respect to the field and high voltage at high frequency without electrode bubble generation are the reasons why the current pump is superior to earlier dc and ac EO pumps. PMID:19693362

Finding the lost open-circuit voltage in polymer solar cells by UV-ozone treatment of the nickel acetate anode buffer layer.

PubMed

Wang, Fuzhi; Sun, Gang; Li, Cong; Liu, Jiyan; Hu, Siqian; Zheng, Hua; Tan, Zhan'ao; Li, Yongfang

2014-06-25

Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Voc in comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Voc increases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Voc value of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%.

Automatic control and detector for three-terminal resistance measurement

DOEpatents

Fasching, George E.

1976-10-26

A device is provided for automatic control and detection in a three-terminal resistance measuring instrument. The invention is useful for the rapid measurement of the resistivity of various bulk material with a three-terminal electrode system. The device maintains the current through the sample at a fixed level while measuring the voltage across the sample to detect the sample resistance. The three-electrode system contacts the bulk material and the current through the sample is held constant by means of a control circuit connected to a first of the three electrodes and works in conjunction with a feedback controlled amplifier to null the voltage between the first electrode and a second electrode connected to the controlled amplifier output. An A.C. oscillator provides a source of sinusoidal reference voltage of the frequency at which the measurement is to be executed. Synchronous reference pulses for synchronous detectors in the control circuit and an output detector circuit are provided by a synchronous pulse generator. The output of the controlled amplifier circuit is sampled by an output detector circuit to develop at an output terminal thereof a D.C. voltage which is proportional to the sample resistance R. The sample resistance is that segment of the sample between the area of the first electrode and the third electrode, which is connected to ground potential.

A Transformerless Hybrid Active Filter Capable of Complying with Harmonic Guidelines for Medium-Voltage Motor Drives

NASA Astrophysics Data System (ADS)

Kondo, Ryota; Akagi, Hirofumi

This paper presents a transformerless hybrid active filter that is integrated into medium-voltage adjustable-speed motor drives for fans, pumps, and compressors without regenerative braking. The authors have designed and constructed a three-phase experimental system rated at 400V and 15kW, which is a downscaled model from a feasible 6.6-kV 1-MW motor drive system. This system consists of the hybrid filter connecting a passive filter tuned to the 7th harmonic filter in series with an active filter that is based on a three-level diode-clamped PWM converter, as well as an adjustable-speed motor drive in which a diode rectifier is used as the front end. The hybrid filter is installed on the ac side of the diode rectifier with no line-frequency transformer. The downscaled system has been exclusively tested so as to confirm the overall compensating performance of the hybrid filter and the filtering performance of a switching-ripple filter for mitigating switching-ripple voltages produced by the active filter. Experimental results verify that the hybrid filter achieves harmonic compensation of the source current in all the operating regions from no-load to the rated-load conditions, and that the switching-ripple filter reduces the switching-ripple voltages as expected.

Contact angle hysteresis and oil film lubrication in electrowetting with two immiscible liquids

NASA Astrophysics Data System (ADS)

Gao, J.; Mendel, N.; Dey, R.; Baratian, D.; Mugele, F.

2018-05-01

Electrowetting (EW) of water drops in ambient oil has found a wide range of applications including lab-on-a-chip devices, display screens, and variable focus lenses. The efficacy of all these applications is dependent on the contact angle hysteresis (CAH), which is generally reduced in the presence of ambient oil due to thin lubrication layers. While it is well-known that AC voltage reduces the effective contact angle hysteresis (CAH) for EW in ambient air, we demonstrate here that CAH for EW in ambient oil increases with increasing AC and DC voltage. Taking into account the disjoining pressure of the fluoropolymer-oil-water system, short range chemical interactions, viscous oil entrainment, and electrostatic stresses, we find that this observation can be explained by progressive thinning of the oil layer underneath the drop with increasing voltage. This exposes the droplet to the roughness of the underlying solid and thereby increases hysteresis.

Hybrid renewable energy system using doubly-fed induction generator and multilevel inverter

NASA Astrophysics Data System (ADS)

Ahmed, Eshita

The proposed hybrid system generates AC power by combining solar and wind energy converted by a doubly-fed induction generator (DFIG). The DFIG, driven by a wind turbine, needs rotor excitation so the stator can supply a load or the grid. In a variable-speed wind energy system, the stator voltage and its frequency vary with wind speed, and in order to keep them constant, variable-voltage and variable-frequency rotor excitation is to be provided. A power conversion unit supplies the rotor, drawing power either from AC mains or from a PV panel depending on their availability. It consists of a multilevel inverter which gives lower harmonic distortion in the stator voltage. Maximum power point tracking techniques have been implemented for both wind and solar power. The complete hybrid renewable energy system is implemented in a PSIM-Simulink interface and the wind energy conversion portion is realized in hardware using dSPACE controller board.

Numerical Study on Alternating Current Breakdown Mechanism Between Sphere-Sphere Electrodes in Transformer Oil-Based Magnetic Nanofluids.

PubMed

Lee, Won-Ho; Lee, Jong-Chul

2018-09-01

A numerical simulation was developed for magnetic nanoparticles in a liquid dielectric to investigate the AC breakdown voltage of the magnetic nanofluids according to the volume concentration of the magnetic nanoparticles. In prior research, we found that the dielectric breakdown voltage of the transformer oil-based magnetic nanofluids was positively or negatively affected according to the amount of magnetic nanoparticles under a testing condition of dielectric fluids, and the trajectory of the magnetic nanoparticles in a fabricated chip was visualized to verify the related phenomena via measurements and computations. In this study, a numerical simulation of magnetic nanoparticles in an insulating fluid was developed to model particle tracing for AC breakdown mechanisms happened to a sphere-sphere electrode configuration and to propose a possible mechanism regarding the change in the breakdown strength due to the behavior of the magnetic nanoparticles with different applied voltages.

Electric power processing, distribution and control for advanced aerospace vehicles.

NASA Technical Reports Server (NTRS)

Krausz, A.; Felch, J. L.

1972-01-01

The results of a current study program to develop a rational basis for selection of power processing, distribution, and control configurations for future aerospace vehicles including the Space Station, Space Shuttle, and high-performance aircraft are presented. Within the constraints imposed by the characteristics of power generation subsystems and the load utilization equipment requirements, the power processing, distribution and control subsystem can be optimized by selection of the proper distribution voltage, frequency, and overload/fault protection method. It is shown that, for large space vehicles which rely on static energy conversion to provide electric power, high-voltage dc distribution (above 100 V dc) is preferable to conventional 28 V dc and 115 V ac distribution per MIL-STD-704A. High-voltage dc also has advantages over conventional constant frequency ac systems in many aircraft applications due to the elimination of speed control, wave shaping, and synchronization equipment.

Improved power control using optimal adjustable coefficients for three-phase photovoltaic inverter under unbalanced grid voltage.

PubMed

Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

2014-01-01

Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software.

Improved Power Control Using Optimal Adjustable Coefficients for Three-Phase Photovoltaic Inverter under Unbalanced Grid Voltage

PubMed Central

Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

2014-01-01

Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software. PMID:25243215

Lighting Systems For High Speed Photography Applying Special Metal Halide Discharge Lamps

NASA Astrophysics Data System (ADS)

Gillum, Keith M.; Steuernagel, K. H.

1983-03-01

High speed photography requires, in addition to a good color quality of the light source, a very high level of illumination. Conventional lighting systems utilizing incandescent lamps or other metal halide lamp types has inherent problems of inefficient light output or poor color quality. Heat generated by incandescent lamps and the power these sources require drive up operating and installation costs. A most economical and practical solution was devised by using the metal halide discharge lamp developed by OSRAM, GmbH of Munich, West Germany. This lamp trade marked the HMITM Metallogen was primarily developed for the needs of the television and motion picture film industry. Due to their high efficiency and other consistent operating qualities these lamps also fulfill the needs of high speed photography, e.g. in crash test facilities, when special engineering activities are carried out. The OSRAM HMITM lamp is an AC discharge metal halide lamp with rare earth additives to increase both the efficiency and light output qualities. Since the lamp is an AC source, a special method had to be developed to overcome the strobing effect, which is normal for AC lamps given their modulated light output, when used with high speed cameras, (e.g. with >1000 fps). This method is based on an increased frequency for the lamp supply voltage coupled with a mix of the light output achieved using a multiphase mains power supply. First developed in 1977, this system using the OSRAM HMITM lamps was installed in a crash test facility of a major automotive manufacturer in West Germany. The design resulted in the best lighting and performance ever experienced. Since that time several other motor companies have made use of this breakthrough. Industrial and scientific users are now considering additional applications use of this advanced high speed lighting system.

Impact analysis of tap switch out of step for converter transformer

NASA Astrophysics Data System (ADS)

Hong-yue, ZHANG; Zhen-hua, ZHANG; Zhang-xue, XIONG; Gao-wang, YU

2017-06-01

AC transformer load regulation is mainly used to adjust the load side voltage level, improve the quality of power supply, the voltage range is relatively narrow. In DC system, converter transformer is the core equipment of AC and DC power converter and inverter. converter transformer tap adjustment can maintain the normal operation of the converter in small angle range control, the absorption of reactive power, economic operation, valve less stress, valve damping circuit loss, AC / DC harmonic component is also smaller. In this way, the tap switch action is more frequent, and a large range of the tap switch adjustment is required. Converter transformer with a more load voltage regulation switch, the voltage regulation range of the switch is generally 20~30%, the adjustment of each file is 1%~2%. Recently it is often found that the tap switch of Converter Transformers is out of step in Converter station. In this paper, it is analyzed in detail the impact of tap switch out of step for differential protection, overexcitation protection and zero sequence over current protection. Analysis results show that: the tap switch out of step has no effect on the differential protection and the overexcitation protection including the tap switch. But the tap switch out of step has effect on zero sequence overcurrent protection of out of step star-angle converter transformer. The zero sequence overcurrent protection will trip when the tap switch out of step is greater than 3 for out of step star-angle converter transformer.

Nonlinear magnetoelectric effects at high magnetic field amplitudes in composite multiferroics

NASA Astrophysics Data System (ADS)

Fetisov, L. Y.; Burdin, D. A.; Ekonomov, N. A.; Chashin, D. V.; Zhang, J.; Srinivasan, G.; Fetisov, Y. K.

2018-04-01

Magnetoelectric effects (ME) in ferromagnetic-ferroelectric layered composites arise due to magnetostriction and piezoelectric effect in the ferroic phases and are mediated by mechanical strain. The ME coupling strength in such composites could be measured by electrical response to an applied ac magnetic field h and a bias magnetic field H. The coupling, in general, is linear for small ac field amplitudes, but one expects nonlinear ME interactions for high field strengths since the dependence of magnetostriction λ on magnetic fields is nonlinear. Here we report on nonlinear voltage response of a composite of ferromagnetic Metglas and piezoelectric lanthanum gallium tantalate (langatate) subjected to an ac and a bias magnetic fields, resulting in the generation of voltages at harmonics of the frequency of h. The dependences of the ME voltage of the first four harmonics on the magnetic fields for H  =  0–20 Oe and h  =  0–50 Oe were measured. Up to a hundred harmonics were observed in the voltage versus frequency spectra and was indicative of high nonlinearity of the ME coupling in the multiferroic structure. It is shown that for h smaller than the saturation magnetic field H S for magnetostriction in the ferromagnetic layer, the amplitudes of the ME voltages are proportional to the derivatives of λ with respect to H and show a power-law dependence on the pumping field amplitude A n (H) ~ λ (n)(H)h n . We discuss a procedure for estimating the amplitudes of the harmonics for large pumping fields h, on the order of H S. The nonlinear ME effects in the composites are of interest for application in signal processing devices and highly sensitive magnetic field sensors.

Brushless exciters using a high temperature superconducting field winding

DOEpatents

Garces, Luis Jose [Schenectady, NY; Delmerico, Robert William [Clifton Park, NY; Jansen, Patrick Lee [Scotia, NY; Parslow, John Harold [Scotia, NY; Sanderson, Harold Copeland [Tribes Hill, NY; Sinha, Gautam [Chesterfield, MO

2008-03-18

A brushless exciter for a synchronous generator or motor generally includes a stator and a rotor rotatably disposed within the stator. The rotor has a field winding and a voltage rectifying bridge circuit connected in parallel to the field winding. A plurality of firing circuits are connected the voltage rectifying bridge circuit. The firing circuit is configured to fire a signal at an angle of less than 90.degree. or at an angle greater than 90.degree.. The voltage rectifying bridge circuit rectifies the AC voltage to excite or de-excite the field winding.

Simulation study on transient electric shock characteristics of human body under high voltage ac transmission lines

NASA Astrophysics Data System (ADS)

Huang, Tao; Zou, Yanhui; Lv, Jianhong; Yang, Jinchun; Tao, Li; Zhou, Jianfei

2017-09-01

Human body under high-voltage AC transmission lines will produce a certain induced voltage due to the electrostatic induction. When the human body contacts with some grounded objects, the charges transfer from the body to the ground and produce contact current which may cause transient electric shock. Using CDEGS and ATP/EMTP, the paper proposes a method for quantitatively calculating the transient electric shock characteristics. It calculates the human body voltage, discharge current and discharge energy under certain 500kV compact-type transmission lines and predicts the corresponding human feelings. The results show that the average root value of discharge current is less than 10mA when the human body is under the 500kV compact-type transmission lines and the human body is overall safe if the transmission lines satisfy the relevant design specifications. It concludes that the electric field strength above the ground should be limited to 4kV/m through the residential area for the purpose of reducing the electromagnetic impact.

Nonlinear system identification of the reduction nickel oxide smelting process in electric arc furnace

NASA Astrophysics Data System (ADS)

Gubin, V.; Firsov, A.

2018-03-01

As the title implies the article describes the nonlinear system identification of the reduction smelting process of nickel oxide in electric arc furnaces. It is suggested that for operational control ratio of components of the charge must be solved the problem of determining the qualitative composition of the melt in real time. The use of 0th harmonic of phase voltage AC furnace as an indirect measure of the melt composition is proposed. Brief description of the mechanism of occurrence and nature of the non-zero 0th harmonic of the AC voltage of the arc is given. It is shown that value of 0th harmonic of the arc voltage is not function of electrical parameters but depends of the material composition of the melt. Processed industrial data are given. Hammerstein-Wiener model is used for description of the dependence of 0th harmonic of the furnace voltage from the technical parameters of melting furnace: the melt composition and current. Recommendations are given about the practical use of the model.

Discreteness-induced resonances and ac voltage amplitudes in long one-dimensional Josephson junction arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duwel, A.E.; Watanabe, S.; Trias, E.

1997-11-01

New resonance steps are found in the experimental current-voltage characteristics of long, discrete, one-dimensional Josephson junction arrays with open boundaries and in an external magnetic field. The junctions are underdamped, connected in parallel, and dc biased. Numerical simulations based on the discrete sine-Gordon model are carried out, and show that the solutions on the steps are periodic trains of fluxons, phase locked by a finite amplitude radiation. Power spectra of the voltages consist of a small number of harmonic peaks, which may be exploited for possible oscillator applications. The steps form a family that can be numbered by the harmonicmore » content of the radiation, the first member corresponding to the Eck step. Discreteness of the arrays is shown to be essential for appearance of the higher order steps. We use a multimode extension of the harmonic balance analysis, and estimate the resonance frequencies, the ac voltage amplitudes, and the theoretical limit on the output power on the first two steps. {copyright} {ital 1997 American Institute of Physics.}« less

Power Packaging of Spray-Cooled SiC Devices for High Temperature and High Voltage Operation: Final Report

DTIC Science & Technology

2008-07-01

the desired switching frequencies. * I Three- r1aL phase dc-ac ac-dc Vph converter # 4 convertr converter 1 # 2 # 3 * I r --- -- -- - 4I6l kV ACSIDE...J:-----------------.HWn.XEMEL ------- J WDC_ SI CEI.................... ... .. .. .............. .......... J . Fig. 4.1 Block diagram of a PCM4. Vph

Three-Phase and Six-Phase AC at the Lab Bench

ERIC Educational Resources Information Center

Caplan, George M.

2009-01-01

Utility companies generate three-phase electric power, which consists of three sinusoidal voltages with phase angles of 0 degrees, 120 degrees, and 240 degrees. The ac generators described in most introductory textbooks are single-phase generators, so physics students are not likely to learn about three-phase power. I have developed a simple way…

Solar electric state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bumke, D.

The booming sales of photovoltaic (PV) equipment in California is described. Three types of markets appear to exist. These are: (1) people who want to electrify a remote home and avoid the large expense of a utility hook-up; (2) suburban renegades who are reluctant to depend on the grid; and (3) the marijuana farmers of northern California who do not want public exposure. Several PV systems and homes are described and illustrated. Various options of electrical systems (ac generators versus electronic inverters) are discussed and the merits of each system are pointed out. Expenses involved in PV systems are describedmore » and various voltage and battery options (12, 24, 36, or 48 volts) are discussed. Specific use of ac or dc for particular appliances is considered in detail. It is estimated that in California more than 500 homes are being powered by over 130,000 watts of PV power. It is predicted that the use of PV's will double in the next year. Sources of information on PV's (catalogs and books) are given. (MJJ)« less

A new venous infusion path monitoring system utilizing electrostatic induced potential.

PubMed

Ogawa, Hidekuni; Yonezawa, Yoshiharu; Maki, Hiromichi; Caldwell, W Morton

2008-01-01

A new venous infusion pathway monitoring system has been developed for hospital and home use. The system consists of linear and digital integrated circuits and a low-power 8-bit single chip microcomputer which constantly monitors the infusion pathway intactness. A 330 kHz AC voltage, which is induced on the patient's body by electrostatic coupling from a 330 kHz pulse oscillator, can be recorded by main and reference electrodes wrapped around the infusion polyvinyl chloride tube. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltages and alerts the nursing station, via the nurse call system or PHS (personal handy phone system).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Kyri; Dall'Anese, Emiliano; Summers, Tyler

This paper outlines a data-driven, distributionally robust approach to solve chance-constrained AC optimal power flow problems in distribution networks. Uncertain forecasts for loads and power generated by photovoltaic (PV) systems are considered, with the goal of minimizing PV curtailment while meeting power flow and voltage regulation constraints. A data- driven approach is utilized to develop a distributionally robust conservative convex approximation of the chance-constraints; particularly, the mean and covariance matrix of the forecast errors are updated online, and leveraged to enforce voltage regulation with predetermined probability via Chebyshev-based bounds. By combining an accurate linear approximation of the AC power flowmore » equations with the distributionally robust chance constraint reformulation, the resulting optimization problem becomes convex and computationally tractable.« less

Matrix Converter Interface for a Wind Energy Conversion System: Issues and Limitations

NASA Astrophysics Data System (ADS)

Patki, Chetan; Agarwal, Vivek

2009-08-01

Variable speed grid connected wind energy systems sometimes involve AC-AC power electronic interface between the generator and the grid. Matrix converter is an attractive option for such applications. Variable speed of the wind generator demands variable voltage variable frequency at the generator terminal. Matrix converter is used in this work to generate such a supply. Also, matrix converter can be appropriately controlled to compensate the grid for non-linear, reactive loads. However, any change of power factor on the grid side reflects on the voltage magnitude on the wind generator side. It is highlighted that this may contradict the maximum power point tracking control requirements. All the results of this work are presented.

A new LTPS TFT AC pixel circuit for an AMOLED

NASA Astrophysics Data System (ADS)

Yongwen, Zhang; Wenbin, Chen

2013-01-01

This work presents a new voltage programmed pixel circuit for an active-matrix organic light-emitting diode (AMOLED) display. The proposed pixel circuit consists of six low temperature polycrystalline silicon thin-film transistors (LTPS TFTs), one storage capacitor, and one OLED, and is verified by simulation work using HSPICE software. Besides effectively compensating for the threshold voltage variation of the driving TFT and OLED, the proposed pixel circuit offers an AC driving mode for the OLED, which can suppress the degradation of the OLED. Moreover, a high contrast ratio can be achieved by the proposed pixel circuit since the OLED does not emit any light except for the emission period.

Flash x-ray generator having a liquid-anode diode

NASA Astrophysics Data System (ADS)

Oizumi, Teiji; Sato, Eiichi; Shikoda, Arimitsu; Sagae, Michiaki; Takahashi, Kei; Tamakawa, Yoshiharu; Yanagisawa, Toru; Ojima, Hidenori; Takayama, Kazuyoshi; Fujiwara, Akihiro; Mitoya, Kanji

1995-05-01

The constructions and the fundamental studies of a flash x-ray generator having a liquid-anode diode are described. This flash x-ray generator consisted of the following essential components: a high-voltage power supply, a high-voltage pulser, a thyratron pulser as a trigger device, an oil diffusion pump, and a flash x-ray tube. The main condenser was negatively charged from 50 to 70 kV by the power supply, and the electric charges in the condenser were discharged to the x-ray tube after closing a gap switch by using the thyratron pulser. The flash x- ray tube was of a diode type having a mercury anode and a ferrite cathode. The pressure of the tube was primarily determined by the steam pressure of mercury as a function of temperature. The maximum output voltage from the pulser was about -1 times the charged voltage. The maximum tube voltage and current were approximately 60 kV and 3 kA, respectively, with a charged voltage of -60 kV and a space between the anode and cathode electrodes (AC space) of 2.0 mm. The pulse widths of flash x rays were about 50 ns, and the x-ray intensity measured by a thermoluminescence dosimeter had a value of about 2.5 (mu) C/kg at 0.3 m per pulse with a charged voltage of -70 kV and an AC space of 1.0 mm.

Fundamental Study on Self-healing Insulation Performance of Silicone Rubber Affected by Local Breakdown

NASA Astrophysics Data System (ADS)

Hozumi, Naohiro; Nishioka, Koji; Suematsu, Takeshi; Murakami, Yoshinobu; Nagao, Masayuki; Sakata, Hiroshi

Feasibility of self-healing insulation system was studied. A silicone rubber without filler was mounted on a glass substrate with a needle electrode. An ac voltage with 4 kV in rms was applied. The voltage was cut off when the tree had propagated into 150 micrometers in length. After the cut-off, the partial discharge inception voltage was periodically observed. The partial discharge inception voltage had once reduced into as low as 2 kV. However, it gradually increased with time, and finally exceeded the tree inception voltage (4 kV) when 30 - 60 hours had passed. It was also observed by optical microscope that the tree gradually disappeared in parallel with the recovery of the partial discharge inception voltage. The same phenomenon was observed even if 1 kV ac voltage had been continuously applied during the process of the recovery. A simulation using a needle-shaped void was performed in order to clarify the mechanism of the self-healing effect. It was observed that the tip of the needle-shaped void gradually got wet with a liquid material. It would be the result of "bleed-out" of the low molecular component included in the rubber. The tip of the void was finally filled with the liquid, however, the rest of the needle-shaped void stayed without being filled. In this type of tree, it was suggested that the self-healing effect is expected if the diameter of the tree did not exceed ca. 5 micrometers.

Assessment on the influence of resistive superconducting fault current limiter in VSC-HVDC system

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Park, Byung-Bae; Lee, Bang-Wook

2014-09-01

Due to fewer risk of commutation failures, harmonic occurrences and reactive power consumptions, Voltage Source Converter (VSC) based HVDC system is known as the optimum solution of HVDC power system for the future power grid. However, the absence of suitable fault protection devices for HVDC system hinders the efficient VSC-HVDC power grid design. In order to enhance the reliability of the VSC-HVDC power grid against the fault current problems, the application of resistive Superconducting Fault Current Limiters (SFCLs) could be considered. Also, SFCLs could be applied to the VSC-HVDC system with integrated AC Power Systems in order to enhance the transient response and the robustness of the system. In this paper, in order to evaluate the role of SFCLs in VSC-HVDC systems and to determine the suitable position of SFCLs in VSC-HVDC power systems integrated with AC power System, a simulation model based on Korea Jeju-Haenam HVDC power system was designed in Matlab Simulink/SimPowerSystems. This designed model was composed of VSC-HVDC system connected with an AC microgrid. Utilizing the designed VSC-HVDC systems, the feasible locations of resistive SFCLs were evaluated when DC line-to-line, DC line-to-ground and three phase AC faults were occurred. Consequently, it was found that the simulation model was effective to evaluate the positive effects of resistive SFCLs for the effective suppression of fault currents in VSC-HVDC systems as well as in integrated AC Systems. Finally, the optimum locations of SFCLs in VSC-HVDC transmission systems were suggested based on the simulation results.

The Calibration of dc Voltage Standards at NIST

PubMed Central

Field, Bruce F.

1990-01-01

This document describes the procedures used at NIST to calibrate dc voltage standards in terms of the NIST volt. Three calibration services are offered by the Electricity Division: Regular Calibration Service (RCS) of client standard cells at NIST; the Volt Transfer Program (VTP) a process to determine the difference between the NIST volt and the volt as maintained by a group of standard cells in a client laboratory; and the calibration of client solid-state dc voltage standards at NIST. The operational procedures used to compare these voltage standards to NIST voltage standards and to maintain the NIST volt via the ac Josephson effect are discussed. PMID:28179777

Closed Loop Fuzzy Logic Controlled PV Based Cascaded Boost Five-Level Inverter System

NASA Astrophysics Data System (ADS)

Revana, Guruswamy; Kota, Venkata Reddy

2018-04-01

Recent developments in intelligent control methods and power electronics have produced PV based DC to AC converters related to AC drives. Cascaded boost converter and inverter find their way in interconnecting PV and Induction Motor. This paper deals with digital simulation and implementation of closed loop controlled five-level inverter based Photo-Voltaic (PV) system. The objective of this work is to reduce the harmonics using Multi Level Inverter based system. The DC output from the PV panel is boosted using cascaded-boost-converters. The DC output of these cascaded boost converters is applied to the bridges of the cascaded inverter. The AC output voltage is obtained by the series cascading of the output voltage of the two inverters. The investigations are done with Induction motor load. Cascaded boost-converter is proposed in the present work to produce the required DC Voltage at the input of the bridge inverter. A simple FLC is applied to CBFLIIM system. The FLC is proposed to reduce the steady state error. The simulation results are compared with the hardware results. The results of the comparison are made to show the improvement in dynamic response in terms of settling time and steady state error. Design procedure and control strategy are presented in detail.

Improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Jiang, Xiongwei; Peng, Qingjun; Sun, Potao

2018-05-01

Electrical breakdown is an important physical phenomenon in electrical equipment and electronic devices. Many related models and theories of electrical breakdown have been proposed. However, a widely recognized understanding on the following phenomenon is still lacking: impulse breakdown strength which varies with waveform parameters, decrease in the breakdown strength of AC voltage with increasing frequency, and higher impulse breakdown strength than that of AC. In this work, an improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers is proposed based on the Harmonic oscillator model. Simulation and experimental results show that, the energy of trapped charges obtained from AC stress is higher than that of impulse voltage, and the absorbed activation energy increases with the increase in the electric field frequency. Meanwhile, the frequency-dependent relative dielectric constant ε r and dielectric loss tanδ also affect the absorption of activation energy. The absorbed activation energy and modified trap level synergistically determine the breakdown strength. The mechanism analysis of breakdown strength under various voltage waveforms is consistent with the experimental results. Therefore, the proposed model of activation energy absorption in the present work may provide a new possible method for analyzing and explaining the breakdown phenomenon in semi-crystalline insulating polymers.

A novel interface circuit for triboelectric nanogenerator

NASA Astrophysics Data System (ADS)

Yu, Wuqi; Ma, Jiahao; Zhang, Zhaohua; Ren, Tianling

2017-10-01

For most triboelectric nanogenerators (TENGs), the electric output should be a short AC pulse, which has the common characteristic of high voltage but low current. Thus it is necessary to convert the AC to DC and store the electric energy before driving conventional electronics. The traditional AC voltage regulator circuit which commonly consists of transformer, rectifier bridge, filter capacitor, and voltage regulator diode is not suitable for the TENG because the transformer’s consumption of power is appreciable if the TENG output is small. This article describes an innovative design of an interface circuit for a triboelectric nanogenerator that is transformerless and easily integrated. The circuit consists of large-capacity electrolytic capacitors that can realize to intermittently charge lithium-ion batteries and the control section contains the charging chip, the rectifying circuit, a comparator chip and switch chip. More important, the whole interface circuit is completely self-powered and self-controlled. Meanwhile, the chip is widely used in the circuit, so it is convenient to integrate into PCB. In short, this work presents a novel interface circuit for TENGs and makes progress to the practical application and industrialization of nanogenerators. Project supported by the National Natural Science Foundation of China (No. 61434001) and the ‘Thousands Talents’ Program for Pioneer Researchers and Its Innovation Team, China.

Closed Loop Fuzzy Logic Controlled PV Based Cascaded Boost Five-Level Inverter System

NASA Astrophysics Data System (ADS)

Revana, Guruswamy; Kota, Venkata Reddy

2017-12-01

Recent developments in intelligent control methods and power electronics have produced PV based DC to AC converters related to AC drives. Cascaded boost converter and inverter find their way in interconnecting PV and Induction Motor. This paper deals with digital simulation and implementation of closed loop controlled five-level inverter based Photo-Voltaic (PV) system. The objective of this work is to reduce the harmonics using Multi Level Inverter based system. The DC output from the PV panel is boosted using cascaded-boost-converters. The DC output of these cascaded boost converters is applied to the bridges of the cascaded inverter. The AC output voltage is obtained by the series cascading of the output voltage of the two inverters. The investigations are done with Induction motor load. Cascaded boost-converter is proposed in the present work to produce the required DC Voltage at the input of the bridge inverter. A simple FLC is applied to CBFLIIM system. The FLC is proposed to reduce the steady state error. The simulation results are compared with the hardware results. The results of the comparison are made to show the improvement in dynamic response in terms of settling time and steady state error. Design procedure and control strategy are presented in detail.

Disparity between online and offline tests in accelerated aging tests of LED lamps under electric stress.

PubMed

Wang, Yao; Jing, Lei; Ke, Hong-Liang; Hao, Jian; Gao, Qun; Wang, Xiao-Xun; Sun, Qiang; Xu, Zhi-Jun

2016-09-20

The accelerated aging tests under electric stress for one type of LED lamp are conducted, and the differences between online and offline tests of the degradation of luminous flux are studied in this paper. The transformation of the two test modes is achieved with an adjustable AC voltage stabilized power source. Experimental results show that the exponential fitting of the luminous flux degradation in online tests possesses a higher fitting degree for most lamps, and the degradation rate of the luminous flux by online tests is always lower than that by offline tests. Bayes estimation and Weibull distribution are used to calculate the failure probabilities under the accelerated voltages, and then the reliability of the lamps under rated voltage of 220 V is estimated by use of the inverse power law model. Results show that the relative error of the lifetime estimation by offline tests increases as the failure probability decreases, and it cannot be neglected when the failure probability is less than 1%. The relative errors of lifetime estimation are 7.9%, 5.8%, 4.2%, and 3.5%, at the failure probabilities of 0.1%, 1%, 5%, and 10%, respectively.

Cold starting of fluorescent lamps - part II: experiments on glow times and electrode damaging

NASA Astrophysics Data System (ADS)

Langer, Reinhard; Paul, Irina; Hilscher, Achim; Horn, Siegfried; Tidecks, Reinhard

2017-01-01

In the present work we present experiments on cold start and the resulting electrode damaging (reducing lamp life) of AC driven fluorescent lamps. The crucial parameter is the glow time, determined from time resolved measurements of lamp voltage and current. The relation between the energy consumed during glow phase and the glow time is studied. It turns out that there is no common threshold of energy until the glow-to-arc transition takes place, but strong energy input into the lamp yields short glow times. The transient behaviour from the glow to the arc regime is investigated and the stable operation points of the arc discharge are determined, yielding an arc discharge voltage-current characteristics of the lamp type investigated. The electrode damage is investigated as a function of the open source voltage and the ballast resistance. Subsequent cold starts lead to an increase of the glow time due to electrode damaging, i.e., the electrode damage accumulates. Different regeneration procedures and their effectiveness are compared. Regeneration burning turns out to be more effective than heating up the electrode. A criterion for avoiding high electrode damage is obtained, indicating that the average power during glow time should exceed 20 W.

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

DOEpatents

Beverly, Leon H.; Hance, Richard D.; Kristalinski, Alexandr L.; Visser, Age T.

1996-01-01

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

DOEpatents

Beverly, L.H.; Hance, R.D.; Kristalinski, A.L.; Visser, A.T.

1996-11-19

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer. 23 figs.

Novel dielectric reduces corona breakdown in ac capacitors

NASA Technical Reports Server (NTRS)

Loehner, J. L.

1972-01-01

Dielectric system was developed which consists of two layers of 25-gage paper separated by one layer of 50-gage polypropylene to reduce corona breakdown in ac capacitors. System can be used in any alternating current application where constant voltage does not exceed 400 V rms. With a little research it could probably be increased to 700 to 800 V rms.

Performance analysis of electronic power transformer based on neuro-fuzzy controller.

PubMed

Acikgoz, Hakan; Kececioglu, O Fatih; Yildiz, Ceyhun; Gani, Ahmet; Sekkeli, Mustafa

2016-01-01

In recent years, electronic power transformer (EPT), which is also called solid state transformer, has attracted great interest and has been used in place of the conventional power transformers. These transformers have many important functions as high unity power factor, low harmonic distortion, constant DC bus voltage, regulated output voltage and compensation capability. In this study, proposed EPT structure contains a three-phase pulse width modulation rectifier that converts 800 Vrms AC to 2000 V DC bus at input stage, a dual active bridge converter that provides 400 V DC bus with 5:1 high frequency transformer at isolation stage and a three-phase two level inverter that is used to obtain AC output at output stage. In order to enhance dynamic performance of EPT structure, neuro fuzzy controllers which have durable and nonlinear nature are used in input and isolation stages instead of PI controllers. The main aim of EPT structure with the proposed controller is to improve the stability of power system and to provide faster response against disturbances. Moreover, a number of simulation results are carried out to verify EPT structure designed in MATLAB/Simulink environment and to analyze compensation ability for voltage harmonics, voltage flicker and voltage sag/swell conditions.

Accurate evaluation of fast threshold voltage shift for SiC MOS devices under various gate bias stress conditions

NASA Astrophysics Data System (ADS)

Sometani, Mitsuru; Okamoto, Mitsuo; Hatakeyama, Tetsuo; Iwahashi, Yohei; Hayashi, Mariko; Okamoto, Dai; Yano, Hiroshi; Harada, Shinsuke; Yonezawa, Yoshiyuki; Okumura, Hajime

2018-04-01

We investigated methods of measuring the threshold voltage (V th) shift of 4H-silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) under positive DC, negative DC, and AC gate bias stresses. A fast measurement method for V th shift under both positive and negative DC stresses revealed the existence of an extremely large V th shift in the short-stress-time region. We then examined the effect of fast V th shifts on drain current (I d) changes within a pulse under AC operation. The fast V th shifts were suppressed by nitridation. However, the I d change within one pulse occurred even in commercially available SiC MOSFETs. The correlation between I d changes within one pulse and V th shifts measured by a conventional method is weak. Thus, a fast and in situ measurement method is indispensable for the accurate evaluation of I d changes under AC operation.

A new method of converter transformer protection without commutation failure

NASA Astrophysics Data System (ADS)

Zhang, Jiayu; Kong, Bo; Liu, Mingchang; Zhang, Jun; Guo, Jianhong; Jing, Xu

2018-01-01

With the development of AC / DC hybrid transmission technology, converter transformer as nodes of AC and DC conversion of HVDC transmission technology, its reliable safe and stable operation plays an important role in the DC transmission. As a common problem of DC transmission, commutation failure poses a serious threat to the safe and stable operation of power grid. According to the commutation relation between the AC bus voltage of converter station and the output DC voltage of converter, the generalized transformation ratio is defined, and a new method of converter transformer protection based on generalized transformation ratio is put forward. The method uses generalized ratio to realize the on-line monitoring of the fault or abnormal commutation components, and the use of valve side of converter transformer bushing CT current characteristics of converter transformer fault accurately, and is not influenced by the presence of commutation failure. Through the fault analysis and EMTDC/PSCAD simulation, the protection can be operated correctly under the condition of various faults of the converter.

AC coupled three op-amp biopotential amplifier with active DC suppression.

PubMed

Spinelli, E M; Mayosky, M A

2000-12-01

A three op-amps instrumentation amplifier (I.A) with active dc suppression is presented. dc suppression is achieved by means of a controlled floating source at the input stage, to compensate electrode and op-amps offset voltages. This isolated floating source is built around an optical-isolated device using a general-purpose optocoupler, working as a photovoltaic generator. The proposed circuit has many interesting characteristics regarding simplicity and cost, while preserving common mode rejection ratio (CMRR) and high input impedance characteristics of the classic three op-amps I.A. As an example, a biopotential amplifier with a gain of 80 dB, a lower cutoff frequency of 0.1 Hz, and a dc input range of +/- 8 mV was built and tested. Using general-purpose op-amps, a CMRR of 105 was achieved without trimmings.

Bridgeless SEPIC PFC Converter for Multistring LED Driver

NASA Astrophysics Data System (ADS)

Jha, Aman; Singh, Bhim

2018-05-01

This paper deals with Power Factor Correction (PFC) in Low Voltage High Current (LVHC) multi-string light emitting diode (LED) using a bridgeless (BL) single ended primary inductance converter (SEPIC). This application is designed for large area LED lighting with illumination control. A multi-mode LED dimming technique is used for the lighting control. The BL-SEPIC PFC converter is used as a load emulator for high power factor. The regulated low voltage from flyback converter is a source power to the synchronous buck converters for multi-string LED driver and forced cooling system for LED junction. The BL-SEPIC PFC converter inductor design is based on Discontinuous Inductor Current Modes (DICM) which provides good PFC at low cost. Test results are found quite satisfactory for universal input AC (90-265 V). There is significant improvement in the power factor and input current Total Harmonic Distortion (THD) with good margin of harmonic limits for lighting IEC 61000-3-2 Class C.

Multilayered Functional Insulation System (MFIS) for AC Power Transmission in High Voltage Hybrid Electrical Propulsion

NASA Technical Reports Server (NTRS)

Lizcano, Maricela

2017-01-01

High voltage hybrid electric propulsion systems are now pushing new technology development efforts for air transportation. A key challenge in hybrid electric aircraft is safe high voltage distribution and transmission of megawatts of power (>20 MW). For the past two years, a multidisciplinary materials research team at NASA Glenn Research Center has investigated the feasibility of distributing high voltage power on future hybrid electric aircraft. This presentation describes the team's approach to addressing this challenge, significant technical findings, and next steps in GRC's materials research effort for MW power distribution on aircraft.

Dielectrophoretic concentration of particles under electrokinetic flow

DOEpatents

Miles, Robin R.; Bettencourt, Kerry A.; Fuller, Christopher K.

2004-09-07

The use of dielectrophoresis to collect particles under the conditions of electrokinetically-driven flow. Dielectrophortic concentration of particles under electrokinetic flow is accomplished by interdigitated electrodes patterned on an inner surface of a microfluid channel, a DC voltage is applied across the ends to the channel, and an AC voltage is applied across the electrodes, and particles swept down the channel electrokinetically are trapped within the field established by the electrodes. The particles can be released when the voltage to the electrodes is released.

High voltage AC/AC electrochemical capacitor operating at low temperature in salt aqueous electrolyte

NASA Astrophysics Data System (ADS)

Abbas, Qamar; Béguin, François

2016-06-01

We demonstrate that an activated carbon (AC)-based electrochemical capacitor implementing aqueous lithium sulfate electrolyte in 7:3 vol:vol water/methanol mixture can operate down to -40 °C with good electrochemical performance. Three-electrode cell investigations show that the faradaic contributions related with hydrogen chemisorption in the negative AC electrode are thermodynamically unfavored at -40 °C, enabling the system to work as a typical electrical double-layer (EDL) capacitor. After prolonged floating of the AC/AC capacitor at 1.6 V and -40°C, the capacitance, equivalent series resistance and efficiency remain constant, demonstrating the absence of ageing related with side redox reactions at this temperature. Interestingly, when temperature is increased back to 24 °C, the redox behavior due to hydrogen storage reappears and the system behaves as a freshly prepared one.

Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

NASA Astrophysics Data System (ADS)

Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

2010-11-01

AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean's critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

Aligning fast alternating current electroosmotic flow fields and characteristic frequencies with dielectrophoretic traps to achieve rapid bacteria detection.

PubMed

Gagnon, Zachary; Chang, Hsueh-Chia

2005-10-01

Tailor-designed alternating current electroosmotic (AC-EO) stagnation flows are used to convect bioparticles globally from a bulk solution to localized dielectrophoretic (DEP) traps that are aligned at the flow stagnation points. The multiscale trap, with a typical trapping time of seconds for a dilute 70 microL volume of 10(3) particles per cc sample, is several orders of magnitude faster than conventional DEP traps and earlier AC-EO traps with parallel, castellated, or finger electrodes. A novel serpentine wire capable of sustaining a high voltage, up to 2500 V(RMS), without causing excessive heat dissipation or Faradaic reaction in strong electrolytes is fabricated to produce the strong AC-EO flow with two separated stagnation lines, one aligned with the field minimum and one with the field maximum. The continuous wire design allows a large applied voltage without inducing Faradaic electrode reactions. Particles are trapped within seconds at one of the traps depending on whether they suffer negative or positive DEP. The particles can also be rapidly released from their respective traps by varying the frequency of the applied AC field below particle-distinct cross-over frequencies. Zwitterion addition to the buffer allows further geometric and frequency alignments of the AC-EO and DEP motions. The same device hence allows fast trapping, detection, sorting, and characterization on a sample with realistic conductivity, volume, and bacteria count.

Non-contact current and voltage sensor

DOEpatents

Carpenter, Gary D; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C; Schappert, Michael A

2014-03-25

A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

Dynamic Scattering Mode LCDs

NASA Astrophysics Data System (ADS)

Bahadur, Birendra

The following sections are included: * INTRODUCTION * CELL DESIGNING * EXPERIMENTAL OBSERVATIONS IN NEMATICS RELATED WITH DYNAMIC SCATTERING * Experimental Observations at D.C. Field and Electrode Effects * Experimental Observation at Low Frequency A.C. Fields * Homogeneously Aligned Nematic Regime * Williams Domains * Dynamic Scattering * Experimental Observation at High Frequency A.C. Field * Other Experimental Observations * THEORETICAL INTERPRETATIONS * Felici Model * Carr-Helfrich Model * D.C. Excitation * Dubois-Violette, de Gennes and Parodi Model * Low Freqency or Conductive Regime * High Frequency or Dielectric Regime * DYNAMIC SCATTERING IN SMECRIC A PHASE * ELECTRO-OPTICAL CHARACTERISTICS AND LIMITATIONS * Contrast Ratio vs. Voltage, Viewing Angle, Cell Gap, Wavelength and Temperature * Display Current vs. Voltage, Cell Gap and Temperature * Switching Time * Effect of Alignment * Effect of Conductivity, Temperature and Frequency * Addressing of DSM LCDs * Limitations of DSM LCDs * ACKNOWLEDGEMENTS * REFERENCES

Magnetic fields and childhood cancer: an epidemiological investigation of the effects of high-voltage underground cables.

PubMed

Bunch, K J; Swanson, J; Vincent, T J; Murphy, M F G

2015-09-01

Epidemiological evidence of increased risks for childhood leukaemia from magnetic fields has implicated, as one source of such fields, high-voltage overhead lines. Magnetic fields are not the only factor that varies in their vicinity, complicating interpretation of any associations. Underground cables (UGCs), however, produce magnetic fields but have no other discernible effects in their vicinity. We report here the largest ever epidemiological study of high voltage UGCs, based on 52,525 cases occurring from 1962-2008, with matched birth controls. We calculated the distance of the mother's address at child's birth to the closest 275 or 400 kV ac or high-voltage dc UGC in England and Wales and the resulting magnetic fields. Few people are exposed to magnetic fields from UGCs limiting the statistical power. We found no indications of an association of risk with distance or of trend in risk with increasing magnetic field for leukaemia, and no convincing pattern of risks for any other cancer. Trend estimates for leukaemia as shown by the odds ratio (and 95% confidence interval) per unit increase in exposure were: reciprocal of distance 0.99 (0.95-1.03), magnetic field 1.01 (0.76-1.33). The absence of risk detected in relation to UGCs tends to add to the argument that any risks from overhead lines may not be caused by magnetic fields.

Hybrid power system intelligent operation and protection involving distributed architectures and pulsed loads

NASA Astrophysics Data System (ADS)

Mohamed, Ahmed

Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system's dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

Influnce of exposure with Xe radiation on heterojunction solar cell a-SiC/c-Si studied by impedance spectroscopy

NASA Astrophysics Data System (ADS)

Perný, M.; Šály, V.; Packa, J.; Mikolášek, M.; Váry, M.; Huran, J.; Hrubčín, L.; Skuratov, V. A.; Arbet, J.

2017-04-01

The photovoltaic efficiency of heterostructures a-SiC/c-Si may be the same or even better in comparison with conventional silicon structures when suitable adjustment of technological parameters is realized. The main advantage of heterojunction formed amorphous SiC thin film and crystalline silicon compared to standard crystalline solar cell lies in high build-in voltage and thus a high open-circuit voltage. Solar cells can be exposed to various influences of hard environment. A deterioration of properties of heterostructures (a-SiC/c-Si) due to irradiation is examined in our paper using impedance spectroscopy method. Xe ions induced damage is reflected in changes of proposed AC equivalent circuit elements. AC equivalent circuit was proposed and verified using numerical simulations. Impedance spectra were also measured at different DC bias voltages due to a more detailed understanding correlation between Xe ions induced damage and transport phenomenon in the heterostructure.

Converse magnetoelectric coupling in NiFe/Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} nanocomposite thin films grown on Si substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Ming; Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000; Hu, Jiamian

2013-11-04

Multiferroic NiFe (∼30 nm)/Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3}(PMN–PT, ∼220 nm) bilayered thin films were grown on common Pt/Ti/SiO{sub 2}/Si substrates by a combination of off-axis magnetron sputtering and sol-gel spin-coating technique. By using AC-mode magneto-optical Kerr effect technique, the change in the Kerr signal (magnetization) of the NiFe upon applying a low-frequency AC voltage to the PMN–PT film was in situ acquired at zero magnetic field. The obtained Kerr signal versus voltage loop essentially tracks the electromechanical strain curve of the PMN–PT thin film, clearly demonstrating a strain-mediated converse magnetoelectric coupling, i.e., voltage-modulated magnetization, in the NiFe/PMN–PT nanocomposite thin films.

Strong mechanically induced effects in DC current-biased suspended Josephson junctions

NASA Astrophysics Data System (ADS)

McDermott, Thomas; Deng, Hai-Yao; Isacsson, Andreas; Mariani, Eros

2018-01-01

Superconductivity is a result of quantum coherence at macroscopic scales. Two superconductors separated by a metallic or insulating weak link exhibit the AC Josephson effect: the conversion of a DC voltage bias into an AC supercurrent. This current may be used to activate mechanical oscillations in a suspended weak link. As the DC-voltage bias condition is remarkably difficult to achieve in experiments, here we analyze theoretically how the Josephson effect can be exploited to activate and detect mechanical oscillations in the experimentally relevant condition with purely DC current bias. We unveil how changing the strength of the electromechanical coupling results in two qualitatively different regimes showing dramatic effects of the oscillations on the DC-voltage characteristic of the device. These include the appearance of Shapiro-type plateaus for weak coupling and a sudden mechanically induced retrapping for strong coupling. Our predictions, measurable in state-of-the-art experimental setups, allow the determination of the frequency and quality factor of the resonator using DC only techniques.

Acoustic Emission Characteristics of Nanocrystalline Porous Silicon Device Driven as an Ultrasonic Speaker

NASA Astrophysics Data System (ADS)

Tsubaki, Kenji; Komoda, Takuya; Koshida, Nobuyoshi

2006-04-01

It is shown that the dc-superimposed driving mode is more useful for the efficient operation of a novel thermally induced ultrasonic emitter based on nanocrystalline porous silicon (nc-PS) than the conventional simple ac-voltage driving mode. The nc-PS device is composed of a patterned heater electrode, an nc-PS layer and a single crystalline silicon (c-Si) substrate. The almost complete thermally insulating property of nc-PS as a quantum-sized system makes it possible to apply the nc-PS device as an ultrasonic generator by efficient thermo acoustic conversion without any mechanical vibrations. In the dc-superimposed driving mode, the output frequency is the same as the input frequency and a stationary temperature rise is kept constant independent of input peak-to-peak voltage. In addition, power efficiency is significantly increases compared with that in the ac-voltage driving mode without affecting on the temperature rise. The present results suggest the further possibility of the nc-PS device being used as a functional speaker.

The impact of model peptides on structural and dynamic properties of egg yolk lecithin liposomes - experimental and DFT studies.

PubMed

Wałęsa, Roksana; Man, Dariusz; Engel, Grzegorz; Siodłak, Dawid; Kupka, Teobald; Ptak, Tomasz; Broda, Małgorzata A

2015-07-01

Electron spin resonance (ESR), (1) H-NMR, voltage and resistance experiments were performed to explore structural and dynamic changes of Egg Yolk Lecithin (EYL) bilayer upon addition of model peptides. Two of them are phenylalanine (Phe) derivatives, Ac-Phe-NHMe (1) and Ac-Phe-NMe2 (2), and the third one, Ac-(Z)-ΔPhe-NMe2 (3), is a derivative of (Z)-α,β-dehydrophenylalanine. The ESR results revealed that all compounds reduced the fluidity of liposome's membrane, and the highest activity was observed for compound 2 with N-methylated C-terminal amide bond (Ac-Phe-NMe2 ). This compound, being the most hydrophobic, penetrates easily through biological membranes. This was also observed in voltage and resistance studies. (1) H-NMR studies provided a sound evidence on H-bond interactions between the studied diamides and lecithin polar head. The most significant changes in H-atom chemical shifts and spin-lattice relaxation times T1 were observed for compound 1. Our experimental studies were supported by theoretical calculations. Complexes EYLAc-Phe-NMe2 and EYLAc-(Z)-ΔPhe-NMe2 , stabilized by NH⋅⋅⋅O or/and CH⋅⋅⋅O H-bonds were created and optimized at M06-2X/6-31G(d) level of theory in vacuo and in H2 O environment. According to our molecular-modeling studies, the most probable lecithin site of H-bond interaction with studied diamides is the negatively charged O-atom in phosphate group which acts as H-atom acceptor. Moreover, the highest binding energy to hydrocarbon chains were observed in the case of Ac-Phe-NMe2 (2). Copyright © 2015 Verlag Helvetica Chimica Acta AG, Zürich.

A new on-chip all-digital three-phase full-bridge dc/ac power inverter with feedforward and frequency control techniques.

PubMed

Chen, Jiann-Jong; Kung, Che-Min

2010-09-01

The communication speed between components is far from satisfactory. To achieve high speed, simple control system configuration, and low cost, a new on-chip all-digital three-phase dc/ac power inverter using feedforward and frequency control techniques is proposed. The controller of the proposed power inverter, called the shift register, consists of six-stage D-latch flip-flops with a goal of achieving low-power consumption and area efficiency. Variable frequency is achieved by controlling the clocks of the shift register. One advantage regarding the data signal (D) and the common clock (CK) is that, regardless of the phase difference between the two, all of the D-latch flip-flops are capable of delaying data by one CK period. To ensure stability, the frequency of CK must be six times higher than that of D. The operation frequency of the proposed power inverter ranges from 10 Hz to 2 MHz, and the maximum output loading current is 0.8 A. The prototype of the proposed circuit has been fabricated with TSMC 0.35 μm 2P4M CMOS processes. The total chip area is 2.333 x 1.698 mm2. The three-phase dc/ac power inverter is applicable in uninterrupted power supplies, cold cathode fluorescent lamps, and motors, because of its ability to convert the dc supply voltage into the three-phase ac power sources.

Impacts on the Voltage Profile of DC Distribution Network with DG Access

NASA Astrophysics Data System (ADS)

Tu, J. J.; Yin, Z. D.

2017-07-01

With the development of electronic, more and more distributed generations (DGs) access into grid and cause the research fever of direct current (DC) distribution network. Considering distributed generation (DG) location and capacity have great impacts on voltage profile, so use IEEE9 and IEEE33 typical circuit as examples, with DGs access in centralized and decentralized mode, to compare voltage profile in alternating and direct current (AC/DC) distribution network. Introducing the voltage change ratio as an evaluation index, so gets the general results on voltage profile of DC distributed network with DG access. Simulation shows that, in the premise of reasonable location and capacity, DC distribution network is more suitable for DG access.

14 CFR 171.259 - Performance requirements: General.

Code of Federal Regulations, 2010 CFR

2010-01-01

... V (±0.2 V).* AC line frequency (60 Hz), 57 Hz to 63 Hz (±0.2 Hz).* DC voltage (48 V), 44 V to 52 V (±0.5 V).* *Note: Where discrete values of the above frequency or voltages are specified for testing... runway localizer and glide path transmitter frequencies of an ISMLS must be in accordance with the...

Large-Signal Lyapunov-Based Stability Analysis of DC/AC Inverters and Inverter-Based Microgrids

NASA Astrophysics Data System (ADS)

Kabalan, Mahmoud

Microgrid stability studies have been largely based on small-signal linearization techniques. However, the validity and magnitude of the linearization domain is limited to small perturbations. Thus, there is a need to examine microgrids with large-signal nonlinear techniques to fully understand and examine their stability. Large-signal stability analysis can be accomplished by Lyapunov-based mathematical methods. These Lyapunov methods estimate the domain of asymptotic stability of the studied system. A survey of Lyapunov-based large-signal stability studies showed that few large-signal studies have been completed on either individual systems (dc/ac inverters, dc/dc rectifiers, etc.) or microgrids. The research presented in this thesis addresses the large-signal stability of droop-controlled dc/ac inverters and inverter-based microgrids. Dc/ac power electronic inverters allow microgrids to be technically feasible. Thus, as a prelude to examining the stability of microgrids, the research presented in Chapter 3 analyzes the stability of inverters. First, the 13 th order large-signal nonlinear model of a droop-controlled dc/ac inverter connected to an infinite bus is presented. The singular perturbation method is used to decompose the nonlinear model into 11th, 9th, 7th, 5th, 3rd and 1st order models. Each model ignores certain control or structural components of the full order model. The aim of the study is to understand the accuracy and validity of the reduced order models in replicating the performance of the full order nonlinear model. The performance of each model is studied in three different areas: time domain simulations, Lyapunov's indirect method and domain of attraction estimation. The work aims to present the best model to use in each of the three domains of study. Results show that certain reduced order models are capable of accurately reproducing the performance of the full order model while others can be used to gain insights into those three areas of study. This will enable future studies to save computational effort and produce the most accurate results according to the needs of the study being performed. Moreover, the effect of grid (line) impedance on the accuracy of droop control is explored using the 5th order model. Simulation results show that traditional droop control is valid up to R/X line impedance value of 2. Furthermore, the 3rd order nonlinear model improves the currently available inverter-infinite bus models by accounting for grid impedance, active power-frequency droop and reactive power-voltage droop. Results show the 3rd order model's ability to account for voltage and reactive power changes during a transient event. Finally, the large-signal Lyapunov-based stability analysis is completed for a 3 bus microgrid system (made up of 2 inverters and 1 linear load). The thesis provides a systematic state space large-signal nonlinear mathematical modeling method of inverter-based microgrids. The inverters include the dc-side dynamics associated with dc sources. The mathematical model is then used to estimate the domain of asymptotic stability of the 3 bus microgrid. The three bus microgrid system was used as a case study to highlight the design and optimization capability of a large-signal-based approach. The study explores the effect of system component sizing, load transient and generation variations on the asymptotic stability of the microgrid. Essentially, this advancement gives microgrid designers and engineers the ability to manipulate the domain of asymptotic stability depending on performance requirements. Especially important, this research was able to couple the domain of asymptotic stability of the ac microgrid with that of the dc side voltage source. Time domain simulations were used to demonstrate the mathematical nonlinear analysis results.

Effect of an ac Perturbation on the Electroosmotic Behavior of a Cation-Exchange Membrane. Influence of the Cation Nature.

PubMed

Barragán, V. M.; Bauzá, C. Ruíz

2001-08-01

The effect of an ac sinusoidal perturbation of known amplitude and frequency superimposed on the usual dc applied electric voltage difference on the electroosmotic flow through a typical cation-exchange membrane has been studied using different monovalent electrolytes. As a general trend, the presence of the ac perturbation increases the value of the electroosmotic flow with respect to the value in the absence of ac perturbation. A dispersion of the electroosmotic permeability on the frequency of the applied ac signal has been found for the three studied electrolytes, observing that the electroosmotic permeability reaches maximum values for some characteristic values of the frequency. This behavior may be related to the different relaxation processes in heterogeneous mediums. Copyright 2001 Academic Press.

Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

NASA Astrophysics Data System (ADS)

Yan, Xinzhu; Li, Jian; Li, Licheng; Huang, Zhengyong; Wang, Feipeng; Wei, Yuan

2016-10-01

In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

The probable source of certain spurious frequencies found in the output of a variable speed generating system using slip recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlin, P W

1989-06-01

As part of US Department of Energy-sponsored research on wind energy, a Mod-O wind turbine was used to drive a variable-speed, wound-rotor, induction generator. Energy resulting from the slip frequency voltage in the generator rotor was rectified to dc, inverted back to utility frequency ac, and injected into the power line. Spurious changing frequencies displayed in the generator output by a spectrum analyzer are caused by ripple on the dc link. No resonances of any of these moving frequencies were seen in spite of the presence of a bank of power factor correcting capacitors. 5 figs.

Free-piston Stirling Engine system considerations for various space power applications

NASA Technical Reports Server (NTRS)

Dochat, George R.; Dhar, Manmohan

1991-01-01

Free-Piston Stirling Engines (FPSE) have the potential to provide high reliability, long life, and efficient operation. Therefore, they are excellent candidates for the dynamic power conversion module of a space-based, power-generating system. FPSE can be coupled with many potential heat sources (radioisotope, solar, or nuclear reactor), various heat input systems (pumped loop, heat pipe), heat rejection (pumped loop or heat pipe), and various power management and distribution systems (ac, dc, high or low voltage, and fixed or variable load). This paper reviews potential space missions that can be met using free-piston Stirling engines and discusses options of various system integration approaches. This paper briefly outlines the program and recent progress.

EPG waveform library for Graphocephala atropunctata (Hemiptera: Cicadellidae): Effect of adhesive, input resistor, and voltage levels on waveform appearance and stylet probing behaviors.

PubMed

Cervantes, Felix A; Backus, Elaine A

2018-05-31

Blue-green sharpshooter, Graphocephala atropunctata, is a native California vector of Xylella fastidiosa (Xf), a foregut-borne bacterium that is the causal agent of Pierce's disease in grapevines. A 3rd-generation, AC-DC electropenetrograph (EPG monitor) was used to record stylet probing and ingestion behaviors of adult G. atropunctata on healthy grapevines. This study presents for the first time a complete, updated waveform library for this species, as well as effects of different electropenetrograph settings and adhesives on waveform appearances. Both AC and DC applied signals were used with input resistor (Ri) levels (amplifier sensitivities) of 10 6 , 10 7 , 10 8 and 10 9  Ohms, as well as two type of adhesives, conducting silver paint and handmade silver glue. Waveform description, characterization of electrical origins (R versus emf components), and proposed biological meanings of waveforms are reported, as well as qualitative differences in waveform appearances observed with different electropenetrograph settings and adhesives. In addition, a quantitative study with AC signal, using two applied voltage levels (50 and 200 mV) and two Ri levels (10 7 and 10 9  Ohms) was performed. Intermediate Ri levels 10 7 and 10 8  Ohms provided EPG waveforms with the greatest amount of information, because both levels captured similar proportions of R and emf components, as supported by appearance, clarity, and definition of waveforms. Similarly, use of a gold wire loop plus handmade silver glue provided more definition of waveforms than a gold wire loop plus commercial conducting silver paint. Qualitative/observational evidence suggested that AC applied signal caused fewer aberrant behaviors/waveforms than DC applied signal. In the quantitative study, behavioral components of the sharpshooter X wave were the most affected by changes in Ri and voltage level. Because the X wave probably represents X. fastidiosa inoculation behavior, future studies of X. fastidiosa inoculation via EPG will require carefully determined instrument settings. An intermediate Ri level such as 10 8  Ohms with low voltage, AC applied signal, and gold wire loop plus silver glue is recommended as the best electropenetrograph methods to conduct future EPG studies of sharpshooter inoculation behaviors on Xf-resistant and -susceptible grapevine. Copyright © 2018. Published by Elsevier Ltd.

Inverter ratio failure detector

NASA Technical Reports Server (NTRS)

Wagner, A. P.; Ebersole, T. J.; Andrews, R. E. (Inventor)

1974-01-01

A failure detector which detects the failure of a dc to ac inverter is disclosed. The inverter under failureless conditions is characterized by a known linear relationship of its input and output voltages and by a known linear relationship of its input and output currents. The detector includes circuitry which is responsive to the detector's input and output voltages and which provides a failure-indicating signal only when the monitored output voltage is less by a selected factor, than the expected output voltage for the monitored input voltage, based on the known voltages' relationship. Similarly, the detector includes circuitry which is responsive to the input and output currents and provides a failure-indicating signal only when the input current exceeds by a selected factor the expected input current for the monitored output current based on the known currents' relationship.

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions.

PubMed

Hung, Chiao-Fang; Yeh, Po-Chen; Chung, Tien-Kan

2017-02-08

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic-mechanical-piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x -axis and y -axis in-plane and z -axis magnetic fields into piezoelectric voltage outputs. Under the x -axis magnetic field (sine-wave, 100 Hz, 0.2-3.2 gauss) and the z -axis magnetic field (sine-wave, 142 Hz, 0.2-3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13-26.15 mV with 8.79 mV/gauss and 1.31-8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x -axis vibration (sine-wave, 100 Hz, 3.5 g) and z -axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on.

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions

PubMed Central

Hung, Chiao-Fang; Yeh, Po-Chen; Chung, Tien-Kan

2017-01-01

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic–mechanical–piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x-axis and y-axis in-plane and z-axis magnetic fields into piezoelectric voltage outputs. Under the x-axis magnetic field (sine-wave, 100 Hz, 0.2–3.2 gauss) and the z-axis magnetic field (sine-wave, 142 Hz, 0.2–3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13–26.15 mV with 8.79 mV/gauss and 1.31–8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x-axis vibration (sine-wave, 100 Hz, 3.5 g) and z-axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on. PMID:28208693

High Power Amplifier and Power Supply

NASA Technical Reports Server (NTRS)

Duong, Johnny; Stride, Scot; Harvey, Wayne; Haque, Inam; Packard, Newton; Ng, Quintin; Ispirian, Julie Y.; Waian, Christopher; Janes, Drew

2008-01-01

A document discusses the creation of a high-voltage power supply (HVPS) that is able to contain voltages up to -20 kV, keep electrical field strengths to below 200 V/mil (approximately equal to 7.87 kV/mm), and can provide a 200-nanosecond rise/fall time focus modulator swinging between cathode potential of 16.3 kV and -19.3 kV. This HVPS can protect the 95-GHz, pulsed extended interaction klystron (EIK) from arcs/discharges from all sources, including those from within the EIK fs vacuum envelope. This innovation has a multi-winding pulse transformer design, which uses new winding techniques to provide the same delays and rise/fall times (less than 10 nanoseconds) at different potential levels ranging from -20 kV to -16 kV. Another feature involves a high-voltage printed-wiring board that was corona-free at -20 kV DC with a 3- kV AC swing. The corona-free multilayer high-voltage board is used to simulate fields of less than 200 V/mil (approximately equal to 7.87 kV/mm) at 20 kV DC. Drive techniques for the modulator FETs (field-effect transistors) (four to 10 in a series) were created to change states (3,000-V swing) without abrupt steps, while still maintaining required delays and transition times. The packing scheme includes a potting mold to house a ten-stage modulator in the space that, in the past, only housed a four-stage modulator. Problems keeping heat down were solved using aluminum oxide substrate in the high-voltage section to limit temperature rise to less than 10 while withstanding -20 kV DC voltage and remaining corona-free.

Energy breakdown in capacitive deionization.

PubMed

Hemmatifar, Ali; Palko, James W; Stadermann, Michael; Santiago, Juan G

2016-11-01

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). We show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Energy breakdown in capacitive deionization

DOE PAGES

Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; ...

2016-08-12

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages.more » We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.« less

Multilayer Piezoelectric Stack Actuator Characterization

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Jones, Christopher M.; Aldrich, Jack B.; Blodget, Chad; Bao, Xioaqi; Badescu, Mircea; Bar-Cohen, Yoseph

2008-01-01

Future NASA missions are increasingly seeking to use actuators for precision positioning to accuracies of the order of fractions of a nanometer. For this purpose, multilayer piezoelectric stacks are being considered as actuators for driving these precision mechanisms. In this study, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and extreme temperatures and voltages. AC signal testing included impedance, capacitance and dielectric loss factor of each actuator as a function of the small-signal driving sinusoidal frequency, and the ambient temperature. DC signal testing includes leakage current and displacement as a function of the applied DC voltage. The applied DC voltage was increased to over eight times the manufacturers' specifications to investigate the correlation between leakage current and breakdown voltage. Resonance characterization as a function of temperature was done over a temperature range of -180C to +200C which generally exceeded the manufacturers' specifications. In order to study the lifetime performance of these stacks, five actuators from one manufacturer were driven by a 60volt, 2 kHz sine-wave for ten billion cycles. The tests were performed using a Lab-View controlled automated data acquisition system that monitored the waveform of the stack electrical current and voltage. The measurements included the displacement, impedance, capacitance and leakage current and the analysis of the experimental results will be presented.

AC electrified jets in a flow-focusing device: Jet length scaling

PubMed Central

García-Sánchez, Pablo; Alzaga-Gimeno, Javier; Baret, Jean-Christophe

2016-01-01

We use a microfluidic flow-focusing device with integrated electrodes for controlling the production of water-in-oil drops. In a previous work, we reported that very long jets can be formed upon application of AC fields. We now study in detail the appearance of the long jets as a function of the electrical parameters, i.e., water conductivity, signal frequency, and voltage amplitude. For intermediate frequencies, we find a threshold voltage above which the jet length rapidly increases. Interestingly, this abrupt transition vanishes for high frequencies of the signal and the jet length grows smoothly with voltage. For frequencies below a threshold value, we previously reported a transition from a well-behaved uniform jet to highly unstable liquid structures in which axisymmetry is lost rather abruptly. These liquid filaments eventually break into droplets of different sizes. In this work, we characterize this transition with a diagram as a function of voltage and liquid conductivity. The electrical response of the long jets was studied via a distributed element circuit model. The model allows us to estimate the electric potential at the tip of the jet revealing that, for any combination of the electrical parameters, the breakup of the jet occurs at a critical value of this potential. We show that this voltage is around 550 V for our device geometry and choice of flow rates. PMID:27375826

AC electrified jets in a flow-focusing device: Jet length scaling.

PubMed

Castro-Hernández, Elena; García-Sánchez, Pablo; Alzaga-Gimeno, Javier; Tan, Say Hwa; Baret, Jean-Christophe; Ramos, Antonio

2016-07-01

We use a microfluidic flow-focusing device with integrated electrodes for controlling the production of water-in-oil drops. In a previous work, we reported that very long jets can be formed upon application of AC fields. We now study in detail the appearance of the long jets as a function of the electrical parameters, i.e., water conductivity, signal frequency, and voltage amplitude. For intermediate frequencies, we find a threshold voltage above which the jet length rapidly increases. Interestingly, this abrupt transition vanishes for high frequencies of the signal and the jet length grows smoothly with voltage. For frequencies below a threshold value, we previously reported a transition from a well-behaved uniform jet to highly unstable liquid structures in which axisymmetry is lost rather abruptly. These liquid filaments eventually break into droplets of different sizes. In this work, we characterize this transition with a diagram as a function of voltage and liquid conductivity. The electrical response of the long jets was studied via a distributed element circuit model. The model allows us to estimate the electric potential at the tip of the jet revealing that, for any combination of the electrical parameters, the breakup of the jet occurs at a critical value of this potential. We show that this voltage is around 550 V for our device geometry and choice of flow rates.

Assessment of three AC electroosmotic flow protocols for mixing in microfluidic channel.

PubMed

Chen, Jia-Kun; Weng, Chi-Neng; Yang, Ruey-Jen

2009-05-07

This study performs an experimental investigation into the micromixer capabilities of three different protocols of AC electroosmotic flow (AC EOF), namely capacitive charging (CC), Faradaic charging (FC) and asymmetric polarization (AP). The results reveal that the vortices generated by the FC protocol (the frequency is around 50-350 Hz) are stronger than those induced by the CC protocol (the frequency is higher than 350 Hz), and therefore provide an improved mixing effect. However, in the FC protocol, the frequency of the external AC voltage must be carefully controlled to avoid damaging electrodes as a result of Faradaic reactions. The experimental results indicate that the AP polarization effect (the applied voltage and frequency are V(1) = 1 V(pp) and V(2) = 20 V(pp)/5 kHz) induces more powerful vortices than either the CC protocol or the FC protocol, and therefore yields a better mixing performance. Two AP-based micromixers are fabricated with symmetric and asymmetric electrode configurations, respectively. The mixing indices achieved by the two devices after an elapsed time of 60 seconds are found to be 56.49 % and 71.77 %, respectively. This result shows that of the two devices, an asymmetric electrode configuration represents a more suitable choice for micromixer in microfluidic devices.

The effect of step height on the performance of three-dimensional ac electro-osmotic microfluidic pumps.

PubMed

Urbanski, John Paul; Levitan, Jeremy A; Burch, Damian N; Thorsen, Todd; Bazant, Martin Z

2007-05-15

Recent numerical and experimental studies have investigated the increase in efficiency of microfluidic ac electro-osmotic pumps by introducing nonplanar geometries with raised steps on the electrodes. In this study, we analyze the effect of the step height on ac electro-osmotic pump performance. AC electro-osmotic pumps with three-dimensional electroplated steps are fabricated on glass substrates and pumping velocities of low ionic strength electrolyte solutions are measured systematically using a custom microfluidic device. Numerical simulations predict an improvement in pump performance with increasing step height, at a given frequency and voltage, up to an optimal step height, which qualitatively matches the trend observed in experiment. For a broad range of step heights near the optimum, the observed flow is much faster than with existing planar pumps (at the same voltage and minimum feature size) and in the theoretically predicted direction of the "fluid conveyor belt" mechanism. For small step heights, the experiments also exhibit significant flow reversal at the optimal frequency, which cannot be explained by the theory, although the simulations predict weak flow reversal at higher frequencies due to incomplete charging. These results provide insight to an important parameter for the design of nonplanar electro-osmotic pumps and clues to improve the fundamental theory of ACEO.

A resettable in-line particle concentrator using AC electrokinetics for distributed monitoring of microalgae in source waters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Quan; Purdue Univ., West Lafayette, IN; Wu, Jayne

Green algae have been studied as an important and effective biomarker to indicate water quality due to their sensitivity to toxic agents in freshwater sources. But, conventional methods to monitor algal physiology use a chlorophyll fluorometer whose use is hampered by high-cost, large footprint, and limited sensitivity for practical samples containing low algal concentration. In order to overcome these constraints, we developed a multi-level electrode platform for resettable trapping of algae via AC electro-osmosis (ACEO) and negative dielectrophoresis. Preliminary experiments were performed in freshwater with conductivity of 0.02 S/m. Algal trapping was demonstrated at a low voltage of 2 V.more » The concentration effect was experimentally verified by measuring the fluorescence intensity of algae and using hemocytometer counting chambers at the inlet and outlet of the multilevel microchannel lab-on-a-chip. An optimal frequency was found for trapping, which agrees with the frequency dependence of ACEO flow velocity. Through-flow rate and electrode dimensions were optimized as well. Trapping efficiencies within the range of 26% - 65% have been obtained. A maximum trapping rate of 182 cells/s was obtained with a flow rate of 20 l/min. Our lab-on-a-chip shows high potential for improving the limit of detection in algal monitoring and enabling the development of a portable, integrated and automated system for monitoring the quality of source drinking waters.« less

A resettable in-line particle concentrator using AC electrokinetics for distributed monitoring of microalgae in source waters

DOE PAGES

Yuan, Quan; Purdue Univ., West Lafayette, IN; Wu, Jayne; ...

2016-12-29

Green algae have been studied as an important and effective biomarker to indicate water quality due to their sensitivity to toxic agents in freshwater sources. But, conventional methods to monitor algal physiology use a chlorophyll fluorometer whose use is hampered by high-cost, large footprint, and limited sensitivity for practical samples containing low algal concentration. In order to overcome these constraints, we developed a multi-level electrode platform for resettable trapping of algae via AC electro-osmosis (ACEO) and negative dielectrophoresis. Preliminary experiments were performed in freshwater with conductivity of 0.02 S/m. Algal trapping was demonstrated at a low voltage of 2 V.more » The concentration effect was experimentally verified by measuring the fluorescence intensity of algae and using hemocytometer counting chambers at the inlet and outlet of the multilevel microchannel lab-on-a-chip. An optimal frequency was found for trapping, which agrees with the frequency dependence of ACEO flow velocity. Through-flow rate and electrode dimensions were optimized as well. Trapping efficiencies within the range of 26% - 65% have been obtained. A maximum trapping rate of 182 cells/s was obtained with a flow rate of 20 l/min. Our lab-on-a-chip shows high potential for improving the limit of detection in algal monitoring and enabling the development of a portable, integrated and automated system for monitoring the quality of source drinking waters.« less

Plasma-based Compressor Stall Control

NASA Astrophysics Data System (ADS)

McGowan, Ryan; Corke, Thomas

2017-11-01

The use of dielectric barrier discharge (DBD) plasma actuator casing treatment to prevent or delay stall inception in an axial fan is examined. The actuators are powered by a pulsed-DC waveform which induces a larger peak velocity than a purely AC waveform such as a sine or sawtooth wave. With this system, a high-voltage DC source is supplied to both electrodes, remaining constant in time for the exposed electrode. Meanwhile, the covered electrode is periodically grounded for several microseconds and allowed to rise back to the source DC level. To test the actuators' ability to interact with and modify the formation of stall cells, a facility has been designed and constructed around nonconductive fan blades. The actuators are installed in the fan casing near the blade tips. The instrumentation allows for the measurement of rotating pressure disturbances (traveling stall cells) in this tip gap region as well as fan performance characteristics including pressure rise and flow rate. The casing plasma actuation is found to reduce the correlation of the rotating stall cells, thereby extending the stall margin of the fan. Various azimuthal arrangements of the plasma actuator casing treatment is explored, as well as input voltage levels to the actuator to determine optimum conditions. NASA SBIR Contract NNX14CC12C.

The mechanism of detection of air pollution by an ionization chamber.

PubMed

Novković, D; Vukanac; Milosević, Z

2000-01-01

The mechanism of detection of chemical vapors in air by an ionization chamber supplied by DC and AC voltage has been described. The theoretical explanation is based on numerical solutions of the differential equations of the cylindrical ionization chamber. The current of the ionization chamber operating in the AC regime has two components: a conductive component, caused by the ions drifts, and a capacitive component, caused by the distortion of the electric field. The ionization chamber operating in the DC regime has only the first component; hence the AC supplied chamber has larger response than the DC supplied chamber.

Observer-based higher order sliding mode control of power factor in three-phase AC/DC converter for hybrid electric vehicle applications

NASA Astrophysics Data System (ADS)

Liu, Jianxing; Laghrouche, Salah; Wack, Maxime

2014-06-01

In this paper, a full-bridge boost power converter topology is studied for power factor control, using output higher order sliding mode control. The AC/DC converters are used for charging the battery and super-capacitor in hybrid electric vehicles from the utility. The proposed control forces the input currents to track the desired values, which can control the output voltage while keeping the power factor close to one. Super-twisting sliding mode observer is employed to estimate the input currents and load resistance only from the measurement of output voltage. Lyapunov analysis shows the asymptotic convergence of the closed-loop system to zero. Multi-rate simulation illustrates the effectiveness and robustness of the proposed controller in the presence of measurement noise.

Distribution-Agnostic Stochastic Optimal Power Flow for Distribution Grids: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Kyri; Dall'Anese, Emiliano; Summers, Tyler

2016-09-01

This paper outlines a data-driven, distributionally robust approach to solve chance-constrained AC optimal power flow problems in distribution networks. Uncertain forecasts for loads and power generated by photovoltaic (PV) systems are considered, with the goal of minimizing PV curtailment while meeting power flow and voltage regulation constraints. A data- driven approach is utilized to develop a distributionally robust conservative convex approximation of the chance-constraints; particularly, the mean and covariance matrix of the forecast errors are updated online, and leveraged to enforce voltage regulation with predetermined probability via Chebyshev-based bounds. By combining an accurate linear approximation of the AC power flowmore » equations with the distributionally robust chance constraint reformulation, the resulting optimization problem becomes convex and computationally tractable.« less

An HF coaxial bridge for measuring impedance ratios up to 1 MHz

NASA Astrophysics Data System (ADS)

Kucera, J.; Sedlacek, R.; Bohacek, J.

2012-08-01

A four-terminal pair coaxial ac bridge developed for calibrating both resistance and capacitance ratios and working in the frequency range from 100 kHz up to 1 MHz is described. A reference inductive voltage divider (IVD) makes it possible to calibrate ratios 1:1 and 10:1 with uncertainty of a few parts in 105. The IVD is calibrated by means of a series-parallel capacitance device (SPCD). Use of the same ac bridge with minimal changes for calibrating the SPCD, IVD and unknown impedances simplifies the whole calibration process. The bridge balance conditions are fulfilled with simple capacitance and resistance decades and by injecting voltage supplied from the auxiliary direct digital synthesizer. Bridge performance was checked on the basis of resistance ratio measurements and also capacitance ratio measurements.

Development of software to improve AC power quality on large spacecraft

NASA Technical Reports Server (NTRS)

Kraft, L. Alan

1991-01-01

To insure the reliability of a 20 kHz, alternating current (AC) power system on spacecraft, it is essential to analyze its behavior under many adverse operating conditions. Some of these conditions include overloads, short circuits, switching surges, and harmonic distortions. Harmonic distortions can become a serious problem. It can cause malfunctions in equipment that the power system is supplying, and, during distortions such as voltage resonance, it can cause equipment and insulation failures due to the extreme peak voltages. To address the harmonic distortion issue, work was begun under the 1990 NASA-ASEE Summer Faculty Fellowship Program. Software, originally developed by EPRI, called HARMFLO, a power flow program capable of analyzing harmonic conditions on three phase, balanced, 60 Hz AC power systems, was modified to analyze single phase, 20 kHz, AC power systems. Since almost all of the equipment used on spacecraft power systems is electrically different from equipment used on terrestrial power systems, it was also necessary to develop mathematical models for the equipment to be used on the spacecraft. The modelling was also started under the same fellowship work period. Details of the modifications and models completed during the 1990 NASA-ASEE Summer Faculty Fellowship Program can be found in a project report. As a continuation of the work to develop a complete package necessary for the full analysis of spacecraft AC power system behavior, deployment work has continued through NASA Grant NAG3-1254. This report details the work covered by the above mentioned grant.

Electrical behaviour of fully solution processed HfO2 (MOS) in presence of different light illumination

NASA Astrophysics Data System (ADS)

Mondal, Sandip

2018-04-01

This experiment demonstrates the electrical behaviors of fully solution processed HfO2(MOS) in presence of different optical illumination. The capacitance voltage measurement was performed at frequency of 100 kHz with a DC gate sweep voltage of ±5V (with additional AC voltage of 100mV) in presence of deep UV (wavelength of 365nm with power of 25W) as well as white light (20W). It is found that there is a large shift in flatband voltage of 120mV due presence of white light during the CV measurement. However there is negligible change in flatband voltage (30mV) has been observed due to illumination of deep UV light.

Integration of HTS Cables in the Future Grid of the Netherlands

NASA Astrophysics Data System (ADS)

Zuijderduin, R.; Chevtchenko, O.; Smit, J. J.; Aanhaanen, G.; Melnik, I.; Geschiere, A.

Due to increasing power demand, the electricity grid of the Netherlands is changing. The future transmission grid will obtain electrical power generated by decentralized renewable sources, together with large scale generation units located at the coastal region. In this way electrical power has to be distributed and transmitted over longer distances from generation to end user. Potential grid issues like: amount of distributed power, grid stability and electrical loss dissipation merit particular attention. High temperature superconductors (HTS) can play an important role in solving these grid problems. Advantages to integrate HTS components at transmission voltages are numerous: more transmittable power together with less emissions, intrinsic fault current limiting capability, lower ac loss, better control of power flow, reduced footprint, less magnetic field emissions, etc. The main obstacle at present is the relatively high price of HTS conductor. However as the price goes down, initial market penetration of several HTS components (e.g.: cables, fault current limiters) is expected by year 2015. In the full paper we present selected ways to integrate EHV AC HTS cables depending on a particular future grid scenario in the Netherlands.

The electrical characteristics of the dielectric barrier discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yehia, Ashraf, E-mail: yehia30161@yahoo.com; Department of Physics, Faculty of Science, Assiut University, Assiut 71516

2016-06-15

The electrical characteristics of the dielectric barrier discharges have been studied in this paper under different operating conditions. The dielectric barrier discharges were formed inside two reactors composed of electrodes in the shape of two parallel plates. The dielectric layers inside these reactors were pasted on the surface of one electrode only in the first reactor and on the surfaces of the two electrodes in the second reactor. The reactor under study has been fed by atmospheric air that flowed inside it with a constant rate at the normal temperature and pressure, in parallel with applying a sinusoidal ac voltagemore » between the electrodes of the reactor. The amount of the electric charge that flows from the reactors to the external circuit has been studied experimentally versus the ac peak voltage applied to them. An analytical model has been obtained for calculating the electrical characteristics of the dielectric barrier discharges that were formed inside the reactors during a complete cycle of the ac voltage. The results that were calculated by using this model have agreed well with the experimental results under the different operating conditions.« less

Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state.

PubMed

Chang, Kuo-Tsai

2007-01-01

This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 k(omega) parallel resistance under open output.

3-V Solid-State Flexible Supercapacitors with Ionic-Liquid-Based Polymer Gel Electrolyte for AC Line Filtering.

PubMed

Kang, Yu Jin; Yoo, Yongju; Kim, Woong

2016-06-08

State-of-the-art solid-state flexible supercapacitors with sufficiently fast response speed for AC line filtering application suffer from limited energy density. One of the main causes of the low energy density is the low cell voltage (1 V), which is limited by aqueous-solution-based gel electrolytes. In this work, we demonstrate for the first time a 3-V flexible supercapacitor for AC line filtering based on an ionic-liquid-based polymer gel electrolyte and carbon nanotube electrode material. The flexible supercapacitor exhibits an areal energy density that is more than 20 times higher than that of the previously demonstrated 1-V flexible supercapacitor (0.66 vs 0.03 μWh/cm(2)) while maintaining excellent capacitive behavior at 120 Hz. The supercapacitor shows a maximum areal power density of 1.5 W/cm(2) and a time constant of 1 ms. The improvement of the cell voltage while maintaining the fast-response capability greatly improves the potential of supercapacitors for high-frequency applications in wearable and/or portable electronics.

Energy storage connection system

DOEpatents

Benedict, Eric L.; Borland, Nicholas P.; Dale, Magdelena; Freeman, Belvin; Kite, Kim A.; Petter, Jeffrey K.; Taylor, Brendan F.

2012-07-03

A power system for connecting a variable voltage power source, such as a power controller, with a plurality of energy storage devices, at least two of which have a different initial voltage than the output voltage of the variable voltage power source. The power system includes a controller that increases the output voltage of the variable voltage power source. When such output voltage is substantially equal to the initial voltage of a first one of the energy storage devices, the controller sends a signal that causes a switch to connect the variable voltage power source with the first one of the energy storage devices. The controller then causes the output voltage of the variable voltage power source to continue increasing. When the output voltage is substantially equal to the initial voltage of a second one of the energy storage devices, the controller sends a signal that causes a switch to connect the variable voltage power source with the second one of the energy storage devices.

Preparation of Power Distribution System for High Penetration of Renewable Energy Part I. Dynamic Voltage Restorer for Voltage Regulation Pat II. Distribution Circuit Modeling and Validation

NASA Astrophysics Data System (ADS)

Khoshkbar Sadigh, Arash

Part I: Dynamic Voltage Restorer In the present power grids, voltage sags are recognized as a serious threat and a frequently occurring power-quality problem and have costly consequence such as sensitive loads tripping and production loss. Consequently, the demand for high power quality and voltage stability becomes a pressing issue. Dynamic voltage restorer (DVR), as a custom power device, is more effective and direct solutions for "restoring" the quality of voltage at its load-side terminals when the quality of voltage at its source-side terminals is disturbed. In the first part of this thesis, a DVR configuration with no need of bulky dc link capacitor or energy storage is proposed. This fact causes to reduce the size of the DVR and increase the reliability of the circuit. In addition, the proposed DVR topology is based on high-frequency isolation transformer resulting in the size reduction of transformer. The proposed DVR circuit, which is suitable for both low- and medium-voltage applications, is based on dc-ac converters connected in series to split the main dc link between the inputs of dc-ac converters. This feature makes it possible to use modular dc-ac converters and utilize low-voltage components in these converters whenever it is required to use DVR in medium-voltage application. The proposed configuration is tested under different conditions of load power factor and grid voltage harmonic. It has been shown that proposed DVR can compensate the voltage sag effectively and protect the sensitive loads. Following the proposition of the DVR topology, a fundamental voltage amplitude detection method which is applicable in both single/three-phase systems for DVR applications is proposed. The advantages of proposed method include application in distorted power grid with no need of any low-pass filter, precise and reliable detection, simple computation and implementation without using a phased locked loop and lookup table. The proposed method has been verified by simulation and experimental tests under various conditions considering all possible cases such as different amounts of voltage sag depth (VSD), different amounts of point-on-wave (POW) at which voltage sag occurs, harmonic distortion, line frequency variation, and phase jump (PJ). Furthermore, the ripple amount of fundamental voltage amplitude calculated by the proposed method and its error is analyzed considering the line frequency variation together with harmonic distortion. The best and worst detection time of proposed method were measured 1ms and 8.8ms, respectively. Finally, the proposed method has been compared with other voltage sag detection methods available in literature. Part 2: Power System Modeling for Renewable Energy Integration: As power distribution systems are evolving into more complex networks, electrical engineers have to rely on software tools to perform circuit analysis. There are dozens of powerful software tools available in the market to perform the power system studies. Although their main functions are similar, there are differences in features and formatting structures to suit specific applications. This creates challenges for transferring power system circuit models data (PSCMD) between different software and rebuilding the same circuit in the second software environment. The objective of this part of thesis is to develop a Unified Platform (UP) to facilitate transferring PSCMD among different software packages and relieve the challenges of the circuit model conversion process. UP uses a commonly available spreadsheet file with a defined format, for any home software to write data to and for any destination software to read data from, via a script-based application called PSCMD transfer application. The main considerations in developing the UP are to minimize manual intervention and import a one-line diagram into the destination software or export it from the source software, with all details to allow load flow, short circuit and other analyses. In this study, ETAP, OpenDSS, and GridLab-D are considered, and PSCMD transfer applications written in MATLAB have been developed for each of these to read the circuit model data provided in the UP spreadsheet. In order to test the developed PSCMD transfer applications, circuit model data of a test circuit and a power distribution circuit from Southern California Edison (SCE) - a utility company - both built in CYME, were exported into the spreadsheet file according to the UP format. Thereafter, circuit model data were imported successfully from the spreadsheet files into above mentioned software using the PSCMD transfer applications developed for each software. After the SCE studied circuit is transferred into OpenDSS software using the proposed UP scheme and developed application, it has been studied to investigate the impacts of large-scale solar energy penetration. The main challenge of solar energy integration into power grid is its intermittency (i.e., discontinuity of output power) nature due to cloud shading of photovoltaic panels which depends on weather conditions. In order to conduct this study, OpenDSS time-series simulation feature, which is required due to intermittency of solar energy, is utilized. In this study, the impacts of intermittency of solar energy penetration, especially high-variability points, on voltage fluctuation and operation of capacitor bank and voltage regulator is provided. In addition, the necessity to interpolate and resample unequally spaced time-series measurement data and convert them to equally spaced time-series data as well as the effect of resampling time-interval on the amount of error is discussed. Two applications are developed in Matlab to do interpolation and resampling as well as to calculate the amount of error for different resampling time-intervals to figure out the suitable resampling time-interval. Furthermore, an approach based on cumulative distribution, regarding the length for lines/cables types and the power rating for loads, is presented to prioritize which loads, lines and cables the meters should be installed at to have the most effect on model validation.

Fluorination effect of activated carbons on performance of asymmetric capacitive deionization

NASA Astrophysics Data System (ADS)

Jo, Hanjoo; Kim, Kyung Hoon; Jung, Min-Jung; Park, Jae Hyun; Lee, Young-Seak

2017-07-01

Activated carbons (ACs) were fluorinated and fabricated into electrodes to investigate the effect of fluorination on asymmetric capacitive deionization (CDI). Fluorine functional groups were introduced on the AC surfaces via fluorination. The specific capacitance of the fluorinated AC (Fsbnd AC) electrode increased drastically from 261 to 337 F/g compared with the untreated AC (Rsbnd AC) electrode at a scan rate of 5 mV/s, despite a decrease in the specific surface area and total pore volume after fluorination. The desalination behavior of asymmetric CDI cells assembled with an Rsbnd AC electrode as the counter electrode and an Fsbnd AC electrode as the cathode (R || F-) or anode (R || F +) was studied. For R || F-, the salt adsorption capacity and charge efficiency increased from 10.6 mg/g and 0.58-12.4 mg/g and 0.75, respectively, compared with the CDI cell assembled with identical Rsbnd AC electrodes at 1 V. This CDI cell exhibited consistently better salt adsorption capacity and charge efficiency at different applied voltages because Fsbnd AC electrodes have a cation attractive effect originating from the partially negatively charged fluorine functional groups on the AC surface. Therefore, co-ion expulsion in the Fsbnd AC electrode as the cathode is effectively diminished, leading to enhanced CDI performance.

Charge control microcomputer device for vehicle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morishita, M.; Kouge, S.

1986-08-26

A charge control microcomputer device is described for a vehicle, comprising: an AC generator driven by an engine for generating an output current, the generator having armature coils and a field coil; a battery charged by a rectified output of the generator and generating a terminal voltage; a voltage regulator for controlling a current flowing in the field coil, to control an output voltage of the generator to a predetermined value; an engine controlling microcomputer for receiving engine parameter data from the engine, to control the operation of the engine; a charge control microcomputer for processing input data including datamore » on at least one engine parameter output from the engine controlling microcomputer, and charge system data including at least one of battery terminal voltage data, generator voltage data and generator output current data, to provide a reference voltage for the voltage regulator.« less

Short-Term State Forecasting-Based Optimal Voltage Regulation in Distribution Systems: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Rui; Jiang, Huaiguang; Zhang, Yingchen

2017-05-17

A novel short-term state forecasting-based optimal power flow (OPF) approach for distribution system voltage regulation is proposed in this paper. An extreme learning machine (ELM) based state forecaster is developed to accurately predict system states (voltage magnitudes and angles) in the near future. Based on the forecast system states, a dynamically weighted three-phase AC OPF problem is formulated to minimize the voltage violations with higher penalization on buses which are forecast to have higher voltage violations in the near future. By solving the proposed OPF problem, the controllable resources in the system are optimally coordinated to alleviate the potential severemore » voltage violations and improve the overall voltage profile. The proposed approach has been tested in a 12-bus distribution system and simulation results are presented to demonstrate the performance of the proposed approach.« less

Investigations into the use of energy storage in power system applications

NASA Astrophysics Data System (ADS)

Leung, Ka Kit

This thesis embodies research work on the design and implementation of novel fast responding battery energy storage systems, which, with sufficient capacity and rating, could remove the uncertainty in forecasting the annual peak demand. They would also benefit the day to day operation by curtailing the fastest demand variations, particularly at the daily peak periods. Energy storage that could curtail peak demands, when the most difficult operational problems occur offers a promising approach. Although AC energy cannot be stored, power electronic developments offer a fast responding interface between the AC network and DC energy stored in batteries. The attractive feature of the use of this energy storage could most effectively be located near the source of load variations, i.e. near consumers in the distribution networks. The proposed, three phase multi-purpose, Battery Energy Storage System will provide active and reactive power independent of the supply voltage with excellent power quality in terms of its waveform. Besides the above important functions applied at the distribution side of the utility, several new topologies have been developed to provide both Dynamic Voltage Regulator (DVR) and Unified Power Flow Controller (UPFC) functions for line compensation. These new topologies can provide fast and accurate control of power flow along a distribution corridor. The topologies also provide for fast damping of system oscillation due to transient or dynamic disturbances. Having demonstrated the various functions that the proposed Battery Energy Storage System can provide, the final part of the thesis investigates means of improving the performance of the proposed BESS. First, there is a need to reduce the switching losses by using soft switching instead of hard switching. A soft switching inverter using a parallel resonant dc-link (PRDCL) is proposed for use with the proposed BESS. The proposed PRDCL suppresses the dc-link voltage to zero for a very short time to allow zero voltage switching of inverter main switches without imposing excessive voltage and current stresses. Finally, in practice the battery terminal voltage fluctuates significantly as large current is being drawn or absorbed by the battery bank. When a hysteresis controller is used to control the supply line current, the ripple magnitude and frequency of the controlled current is highly dependent on the battery voltage, line inductance and the band limits of the controller. Even when these parameters are constant, the switching frequency can vary over quite a large range. A novel method is proposed to overcome this problem by controlling the dc voltage level by means of a dc-dc converter to provide a controllable voltage at the inverter dc terminal irrespective of the battery voltage variations. By proper control of the magnitude and frequency of the output of the DC-DC converter, the switching frequency can be made close to constant. A mathematical proof has been formulated and results from the simulation confirm that using the proposed technique, the frequency band has been significantly reduced and for the theoretical case, a single switching frequency is observed. The main disadvantage is the need to have an extra dc-dc converter, but this is relatively cheap and easy to obtain.

Certain applied electrical signals during EPG cause negative effects on stylet probing behaviors by adult Lygus lineolaris (Hemiptera: Miridae).

PubMed

Backus, Elaine A; Cervantes, Felix A; Godfrey, Larry; Akbar, Waseem; Clark, Thomas L; Rojas, Maria G

This study is the first to fully evaluate whether electrical signals applied to large insects during electropenetrography (EPG; also called electrical penetration graph) negatively affect insect behavior. During EPG, electrical signals are applied to plants, and thus to the gold-wire-tethered insects feeding on them. The insect completes an electrical circuit whose changes in voltage reflect the insect's stylet probing/penetration behaviors, recorded as waveform output. For nearly 50 years of EPG science, evidence has supported that there are no or negligible effects on tiny insects from applied electricity during EPG. Recently however, EPG studies of large-bodied hemipterans such as heteropterans and sharpshooter leafhoppers have been published. The wider stylet diameters of such large insects cause them to have lower inherent resistances to applied signals compared with smaller insects, conveying more electrical current. The present study asked whether such increased currents would affect insect stylet probing, by comparing Lygus lineolaris behaviors on pin-head cotton squares using an AC-DC electropenetrograph. Effects of AC or DC applied signals were separately examined in two factorial studies, each comparing four input resistor (Ri) levels (10 6 , 10 7 , 10 8 and 10 9  Ω) and four applied voltage levels (2, 60, 150 and 250 mV). Results showed that changes in both probing and non-probing behaviors were indeed caused by changing signal type, Ri level, or applied voltage. Negative effects on feeding were numerically greater overall for DC than AC applied signals, perhaps due to muscular tetany from DC; however, AC versus DC could not be statistically tested. Results strongly support the need for flexible Ri and applied voltage levels and types, to tailor instrument settings to the size and special needs of each insect subject. Our findings will facilitate further EPG studies of Lygus spp., such as host plant resistance or insecticidal assays/bioassays to assess mode of action and appropriate dosage. It is hoped that this study will also inform EPG studies of similar, large heteropterans in the future. Published by Elsevier Ltd.

Traceable measurements of the electrical parameters of solid-state lighting products

NASA Astrophysics Data System (ADS)

Zhao, D.; Rietveld, G.; Braun, J.-P.; Overney, F.; Lippert, T.; Christensen, A.

2016-12-01

In order to perform traceable measurements of the electrical parameters of solid-state lighting (SSL) products, it is necessary to technically adequately define the measurement procedures and to identify the relevant uncertainty sources. The present published written standard for SSL products specifies test conditions, but it lacks an explanation of how adequate these test conditions are. More specifically, both an identification of uncertainty sources and a quantitative uncertainty analysis are absent. This paper fills the related gap in the present written standard. New uncertainty sources with respect to conventional lighting sources are determined and their effects are quantified. It shows that for power measurements, the main uncertainty sources are temperature deviation, power supply voltage distortion, and instability of the SSL product. For current RMS measurements, the influence of bandwidth, shunt resistor, power supply source impedance and ac frequency flatness are significant as well. The measurement uncertainty depends not only on the test equipment but is also a function of the characteristics of the device under test (DUT), for example, current harmonics spectrum and input impedance. Therefore, an online calculation tool is provided to help non-electrical experts. Following our procedures, unrealistic uncertainty estimations, unnecessary procedures and expensive equipment can be prevented.

Non-contact current and voltage sensing method using a clamshell housing and a ferrite cylinder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carpenter, Gary D.; El-Essawy, Wael; Ferreira, Alexandre Peixoto

2016-04-26

A method of measurement using a detachable current and voltage sensor provides an isolated and convenient technique for to measuring current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, ormore » alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.« less

Nanosecond pulsed electric fields (nsPEFs) low cost generator design using power MOSFET and Cockcroft-Walton multiplier circuit as high voltage DC source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulaeman, M. Y.; Widita, R.

2014-09-30

Purpose: Non-ionizing radiation therapy for cancer using pulsed electric field with high intensity field has become an interesting field new research topic. A new method using nanosecond pulsed electric fields (nsPEFs) offers a novel means to treat cancer. Not like the conventional electroporation, nsPEFs able to create nanopores in all membranes of the cell, including membrane in cell organelles, like mitochondria and nucleus. NsPEFs will promote cell death in several cell types, including cancer cell by apoptosis mechanism. NsPEFs will use pulse with intensity of electric field higher than conventional electroporation, between 20–100 kV/cm and with shorter duration of pulsemore » than conventional electroporation. NsPEFs requires a generator to produce high voltage pulse and to achieve high intensity electric field with proper pulse width. However, manufacturing cost for creating generator that generates a high voltage with short duration for nsPEFs purposes is highly expensive. Hence, the aim of this research is to obtain the low cost generator design that is able to produce a high voltage pulse with nanosecond width and will be used for nsPEFs purposes. Method: Cockcroft-Walton multiplier circuit will boost the input of 220 volt AC into high voltage DC around 1500 volt and it will be combined by a series of power MOSFET as a fast switch to obtain a high voltage with nanosecond pulse width. The motivation using Cockcroft-Walton multiplier is to acquire a low-cost high voltage DC generator; it will use capacitors and diodes arranged like a step. Power MOSFET connected in series is used as voltage divider to share the high voltage in order not to damage them. Results: This design is expected to acquire a low-cost generator that can achieve the high voltage pulse in amount of −1.5 kV with falltime 3 ns and risetime 15 ns into a 50Ω load that will be used for nsPEFs purposes. Further detailed on the circuit design will be explained at presentation.« less

Development of Vibration-Based Piezoelectric Raindrop Energy Harvesting System

NASA Astrophysics Data System (ADS)

Wong, Chin Hong; Dahari, Zuraini

2017-03-01

The trend of finding new means to harvest energy has triggered numerous researches to explore the potential of raindrop energy harvesting. This paper presents an investigation on raindrop energy harvesting which compares the performance of polyvinylidene fluoride (PVDF) cantilever and bridge structure transducers and the development of a raindrop energy harvesting system. The parameters which contribute to the output voltage such as droplet size, droplets released at specific heights and dimensions of PVDF transducers are analyzed. Based on the experimental results, the outcomes have shown that the bridge structure transducer generated a higher voltage than the cantilever. Several dimensions have been tested and it was found that the 30 mm × 4 mm × 25 μm bridge structure transducer generated a relatively high AC open-circuit voltage, which is 4.22 V. The power generated by the bridge transducer is 18 μW across a load of 330 kΩ. The transducer is able to drive up a standard alternative current (AC) to direct current (DC) converter (full-wave bridge rectifier). It generated a DC voltage, V DC of 8.7 mV and 229 pW across a 330 kΩ resistor per drop. It is also capable to generate 9.3 nJ in 20 s from an actual rain event.

A 65-kV insulated gate bipolar transistor switch applied in damped AC voltages partial discharge detection system.

PubMed

Jiang, J; Ma, G M; Luo, D P; Li, C R; Li, Q M; Wang, W

2014-02-01

Damped AC voltages detection system (DAC) is a productive way to detect the faults in power cables. To solve the problems of large volume, complicated structure and electromagnetic interference in existing switches, this paper developed a compact solid state switch based on electromagnetic trigger, which is suitable for DAC test system. Synchronous electromagnetic trigger of 32 Insulated Gate Bipolar Transistors (IGBTs) in series was realized by the topological structure of single line based on pulse width modulation control technology. In this way, external extension was easily achieved. Electromagnetic trigger and resistor-capacitor-diode snubber circuit were optimized to reduce the switch turn-on time and circular layout. Epoxy encapsulating was chosen to enhance the level of partial discharge initial voltage (PDIV). The combination of synchronous trigger and power supply is proposed to reduce the switch volume. Moreover, we have overcome the drawback of the electromagnetic interference and improved the detection sensitivity of DAC by using capacitor storage energy to maintain IGBT gate driving voltage. The experimental results demonstrated that the solid-state switch, with compact size, whose turn-on time was less than 400 ns and PDIV was more than 65 kV, was able to meet the actual demands of 35 kV DAC test system.

Development of Repulsive Barrier Discharge from Twin Needles

NASA Astrophysics Data System (ADS)

Ueno, Hideki; Hata, Koji; Nakayama, Hiroshi

2007-03-01

Barrier discharge characteristics have been investigated for a twin needles-to-plane electrode configuration in dry air. The characteristics of barrier discharge under ac voltage application have been investigated for various distances between two needle tips (d=1.0--4.0 mm). We have found that corona discharge behavior strongly depends on needle-tip distance. In the case of a twin-needles configuration with a long needle-tip distance (d=4.0 mm), discharges from the two needle tips develop into a dielectric barrier with almost a straight path. On the contrary, the development of repulsive discharges from two needle tips in the gap between needles and a barrier was obtained for the shortest needle-tip distance investigated here (d=1.0 mm) and it was enhanced by increasing the peak voltage. From detailed time-resolved observations, development of repulsive discharge was observed only during positive polarity upon ac voltage application. Moreover, the degree of repulsion increased with increasing applied voltage of positive polarity. The observed unique discharge behavior can be interpreted as the effect of field relaxation induced not only by charge accumulation on the barrier surface, which is markedly enhanced at a short needle-tip distance, but also by space charge by coronas between two needles.

Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Meikap, Ajit Kumar

2017-12-01

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Meikap, Ajit Kumar

2018-06-01

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

Enhancement of discharge performance of Li/CF x cell by thermal treatment of CF x cathode material

NASA Astrophysics Data System (ADS)

Zhang, Sheng S.; Foster, Donald; Read, Jeffrey

In this work we demonstrate that the thermal treatment of CF x cathode material just below the decomposition temperature can enhance discharge performance of Li/CF x cells. The performance enhancement becomes more effective when heating a mixture of CF x and citric acid (CA) since CA serves as an extra carbon source. Discharge experiments show that the thermal treatment not only reduces initial voltage delay, but also raises discharge voltage. Whereas the measurement of powder impedance indicates the thermal treatment does not increase electronic conductivity of CF x material. Based on these facts, we propose that the thermal treatment results in a limited decomposition of CF x, which yields a subfluorinated carbon (CF x- δ), instead of a highly conductive carbon. In the case of CF x/AC mixture, the AC provides extra carbon that reacts with F 2 and fluorocarbon radicals generated by the thermal decomposition of CF x to form subfluorinated carbon. The process of thermal treatment is studied by thermogravimetric analysis and X-ray diffraction, and the effect of treatment conditions such as heating temperature, heating time and CF x/CA ratio on the discharge performance of CF x cathode is discussed. As an example, a Li/CF x cell using CF x treated with CA at 500 °C under nitrogen for 2 h achieved theretical specific capacity when being discharged at C/5. Impedance analysis indicates that the enhanced performance is attributed to a significant reduction in the cell reaction resistance.

Novel design of microgyroscopes employing electrostatic actuation and resistance-change based sensing

NASA Astrophysics Data System (ADS)

Ghommem, M.; Abdelkefi, A.

2017-12-01

The nonlinear dynamics of a microgyroscope consisting of a vibrating beam with attached proof mass and operating at high frequency is numerically investigated. The working principle of this inertial sensor is based on exploiting the transfer of the mechanical energy among two vibrations modes via the Coriolis effect to measure the rotation rate. The flexural motion (drive mode) is generated by applying a DC electrostatic load and an AC harmonic load. We propose a novel sensing technique based on resistance change to detect the induced vibrations of the microbeam (sense mode) and extract the rotation rate. The sensing technique is based on transmitting the Coriolis force acting on the proof mass to a probe that affects the resistance of an electrical circuit acting as a variable voltage divider. This is achieved by integrating the probe dipping μpool (PDP) technology deploying a probe electrode that is dipped into a μpool filled with a conductive nonvolatile fluid. Large magnitude of the AC harmonic load is observed to give rise to dynamic pull-in bandwidth in the frequency response characterized by large and uncontrollable vibrations of the microbeam. Operating near the primary frequency while selecting moderate AC voltage results in linear calibration curves while maintaining high sensitivity of the output voltage to the change in the rotation speed. The simulation results demonstrate the feasibility of the novel technique for sensing the induced vibrations to deliver measurements of the angular speed.

Consumption of the electric power inside silent discharge reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yehia, Ashraf, E-mail: yehia30161@yahoo.com

An experimental study was made in this paper to investigate the relation between the places of the dielectric barriers, which cover the surfaces of the electrodes in the coaxial cylindrical reactors, and the rate of change of the electric power that is consumed in forming silent discharges. Therefore, silent discharges have been formed inside three coaxial cylindrical reactors. The dielectric barriers in these reactors were pasted on both the internal surface of the outer electrode in the first reactor and the external surface of the inner electrode in the second reactor as well as the surfaces of the two electrodesmore » in the third reactor. The reactor under study has been fed by atmospheric air that flowed inside it with a constant rate at normal temperature and pressure, in parallel with the application of a sinusoidal ac voltage between the electrodes of the reactor. The electric power consumed in forming the silent discharges inside the three reactors was measured as a function of the ac peak voltage. The validity of the experimental results was investigated by applying Manley's equation on the same discharge conditions. The results have shown that the rate of consumption of the electric power relative to the ac peak voltage per unit width of the discharge gap improves by a ratio of either 26.8% or 80% or 128% depending on the places of the dielectric barriers that cover the surfaces of the electrodes inside the three reactors.« less

Ozone and dinitrogen monoxide production in atmospheric pressure air dielectric barrier discharge plasma effluent generated by nanosecond pulse superimposed alternating current voltage

NASA Astrophysics Data System (ADS)

Takashima, Keisuke; Kaneko, Toshiro

2017-06-01

The effects of nanosecond pulse superposition to alternating current voltage (NS + AC) on the generation of an air dielectric barrier discharge (DBD) plasma and reactive species are experimentally studied, along with measurements of ozone (O3) and dinitrogen monoxide (N2O) in the exhausted gas through the air DBD plasma (air plasma effluent). The charge-voltage cycle measurement indicates that the role of nanosecond pulse superposition is to induce electrical charge transport and excess charge accumulation on the dielectric surface following the nanosecond pulses. The densities of O3 and N2O in NS + AC DBD are found to be significantly increased in the plasma effluent, compared to the sum of those densities generated in NS DBD and AC DBD operated individually. The production of O3 and N2O is modulated significantly by the phase in which the nanosecond pulse is superimposed. The density increase and modulation effects by the nanosecond pulse are found to correspond with the electrical charge transport and the excess electrical charge accumulation induced by the nanosecond pulse. It is suggested that the electrical charge transport by the nanosecond pulse might result in the enhancement of the nanosecond pulse current, which may lead to more efficient molecular dissociation, and the excess electrical charge accumulation induced by the nanosecond pulse increases the discharge coupling power which would enhance molecular dissociation.

Application of the electroosmotic effect for thrust generation

NASA Astrophysics Data System (ADS)

Hansen, Thomas Edward

The present work focuses on demonstrating the capabilities of electroosmotic pumps, (EOP) to generate thrust. An underwater glider was successfully propelled by electroosmosis for the first time published - at 0.85 inches per second. Asymmetric AC voltage pulsing proved to produce higher flow rates then equivalent DC pumps for the same average voltage. Ultra-short pulsing proved 100 nanosecond rise times in EOP are possible, which surpassed published predictions by three orders of magnitude. Theories behind efficiency losses of high power EOP were investigated. Direct measurement of effective voltage at the face of a membrane is the most accurate way to determine voltage drop across the electrolyte of an EOP. Forced convection lowered efficiency of the EOP for low voltages by preventing capacitance charging, but proved to prolong pump life during high power application.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dall'Anese, Emiliano; Baker, Kyri; Summers, Tyler

The paper focuses on distribution systems featuring renewable energy sources and energy storage devices, and develops an optimal power flow (OPF) approach to optimize the system operation in spite of forecasting errors. The proposed method builds on a chance-constrained multi-period AC OPF formulation, where probabilistic constraints are utilized to enforce voltage regulation with a prescribed probability. To enable a computationally affordable solution approach, a convex reformulation of the OPF task is obtained by resorting to i) pertinent linear approximations of the power flow equations, and ii) convex approximations of the chance constraints. Particularly, the approximate chance constraints provide conservative boundsmore » that hold for arbitrary distributions of the forecasting errors. An adaptive optimization strategy is then obtained by embedding the proposed OPF task into a model predictive control framework.« less

Megajoule Dense Plasma Focus Solid Target Experiments

NASA Astrophysics Data System (ADS)

Podpaly, Y. A.; Falabella, S.; Link, A.; Povilus, A.; Higginson, D. P.; Shaw, B. H.; Cooper, C. M.; Chapman, S.; Bennett, N.; Sipe, N.; Olson, R.; Schmidt, A. E.

2016-10-01

Dense plasma focus (DPF) devices are plasma sources that can produce significant neutron yields from beam into gas interactions. Yield increases, up to approximately a factor of five, have been observed previously on DPFs using solid targets, such as CD2 and D2O ice. In this work, we report on deuterium solid-target experiments at the Gemini DPF. A rotatable target holder and baffle arrangement were installed in the Gemini device which allowed four targets to be deployed sequentially without breaking vacuum. Solid targets of titanium deuteride were installed and systematically studied at a variety of fill pressures, bias voltages, and target positions. Target holder design, experimental results, and comparison to simulations will be presented. Prepared by LLNL under Contract DE-AC52-07NA27344.

An SCR inverter for electric vehicles

NASA Technical Reports Server (NTRS)

Latos, T.; Bosack, D.; Ehrlich, R.; Jahns, T.; Mezera, J.; Thimmesch, D.

1980-01-01

An inverter for an electric vehicle propulsion application has been designed and constructed to excite a polyphase induction motor from a fixed propulsion battery source. The inverter, rated at 35kW peak power, is fully regenerative and permits vehicle operation in both the forward and reverse directions. Thyristors are employed as the power switching devices arranged in a dc bus commutated topology. This paper describes the major role the controller plays in generating the motor excitation voltage and frequency to deliver performance similar to dc systems. Motoring efficiency test data for the controller are presented. It is concluded that an SCR inverter in conjunction with an ac induction motor is a viable alternative to present dc vehicle propulsion systems on the basis of performance and size criteria.

Microfabricated multijunction thermal converters

NASA Astrophysics Data System (ADS)

Wunsch, Thomas Franzen

2001-12-01

In order to develop improved standards for the measurement of ac voltages and currents, a new thin-film fabrication technique for the multijunction thermal converter has been developed. The ability of a thermal converter to relate an rms ac voltage or current to a dc value is characterized by a quantity called `ac-dc difference' that is ideally zero. The best devices produced using the new techniques have ac-dc differences below 1 × 10-6 in the range of frequencies from 20 Hz to 10 kHz and below 7.5 × 10-6 in the range of frequencies from 20 kHz to 300 kHz. This is a reduction of two orders of magnitude in the lower frequency range and one order of magnitude in the higher frequency range over devices produced at the National Institute of Standards and Technology in 1996. The performance achieved is competitive with the best techniques in the world for ac measurements and additional evaluation is therefore warranted to determine the suitability of the devices for use as national standards that form the legal basis for traceable rms voltage measurements of time varying waveforms in the United States. The construction of the new devices is based on thin-film fabrication of a heated wire supported by a thermally isolated thin-film membrane. The membrane is produced utilizing a reactive ion plasma etch. A photoresist lift- off technique is used to pattern the metal thin-film layers that form the heater and the multijunction thermocouple circuit. The etching and lift-off allow the device to be produced without wet chemical etches that are time consuming and impede the investigation of structures with differing materials. These techniques result in an approach to fabrication that is simple, inexpensive, and free from the manual construction techniques used in the fabrication of conventional single and multijunction thermoelements. Thermal, thermoelectric, and electrical models have been developed to facilitate designs that reduce the low- frequency error. At high frequencies, from 300 kHz to 1 MHz, the performance of the device is degraded by a capacitive coupling effect that produces an ac-dc difference of approximately -90 × 10-6 at 1 MHz. A model is developed that explains this behavior. The model shows that an improvement in performance in the high-frequency range is possible through the use of very high or very low resistivity silicon substrates.

Characterizing superconducting thin films using AC Magnetic Susceptibility

NASA Astrophysics Data System (ADS)

Mahoney, C. H.; Porzio, J.; Sullivan, M. C.

2014-03-01

We present our work on using ac magnetic susceptibility to determine the critical temperature of superconducting thin films. In ac magnetic susceptibility, the thin film is placed between two coils. One coil carries an ac signal, creating a varying external magnetic field. We measure the voltage induced in the pick-up coil on the opposite side of the sample and measure how the sample magnetization changes as the temperature changes. We will present our work to use ac susceptibility to determine critical temperature and superconducting volume fraction. Using our own analysis program, we are able to accurately locate the critical temperatures of the samples and determine the transition width. For the superconducting volume fraction, we etch samples in order to control the thicknesses of the sample and measure how much of the material grown on the surface is superconducting. Supported by NFS grant DMR-1305637.

Research on DC Micro-grid system of photovoltaic power generation

NASA Astrophysics Data System (ADS)

Zheng, Yiming; Wang, Xiaohui

2018-01-01

The use of energy has become a topic of concern, the demand of people for power grows in number or quantity with the development of economy. It is necessary to consider using new forms of power supply-microgrid system for distributed power supply. The power supply mode can not only effectively solve the problem of excessive line loss in the large power grid, but also can increase the reliability of the power supply, and is economical and environmental friendly. With the increasing of DC loads, in order to improve the utilization efficiency, the DC microgrid power supply problems are begin to be researched and integrated with the renewable energy sources. This paper researched the development of microgrid, compared AC microgrid with DC microgrid, summarized the distribution of DC bus voltage level, the DC microgrid network form, the control mode and the main power electronics elements of DC microgrid of photovoltaic power generation system. Today, the DC microgrid system is still in the development stage without uniform voltage level standard, however, it will come into service in the future.

Bi-directional flow induced by an AC electroosmotic micropump with DC voltage bias.

PubMed

Islam, Nazmul; Reyna, Jairo

2012-04-01

This paper discusses the principle of biased alternating current electroosmosis (ACEO) and its application to move the bulk fluid in a microchannel, as an alternative to mechanical pumping methods. Previous EO-driven flow research has looked at the effect of electrode asymmetry and transverse traveling wave forms on the performance of electroosmotic pumps. This paper presents an analysis that was conducted to assess the effect of combining an AC signal with a DC (direct current) bias when generating the electric field needed to impart electroosmosis (EO) within a microchannel. The results presented here are numerical and experimental. The numerical results were generated through simulations performed using COMSOL 3.5a. Currently available theoretical models for EO flows were embedded in the software and solved numerically to evaluate the effects of channel geometry, frequency of excitation, electrode array geometry, and AC signal with a DC bias on the flow imparted on an electrically conducting fluid. Simulations of the ACEO flow driven by a constant magnitude of AC voltage over symmetric electrodes did not indicate relevant net flows. However, superimposing a DC signal over the AC signal on the same symmetric electrode array leads to a noticeable net forward flow. Moreover, changing the polarity of electrical signal creates a bi-directional flow on symmetrical electrode array. Experimental flow measurements were performed on several electrode array configurations. The mismatch between the numerical and experimental results revealed the limitations of the currently available models for the biased EO. However, they confirm that using a symmetric electrode array excited by an AC signal with a DC bias leads to a significant improvement in flow rates in comparison to the flow rates obtained in an asymmetric electrode array configuration excited just with an AC signal. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dissection of the Mechanical Impedance Components of the Outer Hair Cell Using a Chloride-Channel Blocker

NASA Astrophysics Data System (ADS)

Harasztosi, Csaba; Gummer, Anthony W.

2011-11-01

The voltage-dependent chloride-channel blocker anthracene-9-carboxylic acid (9AC) has been found to reduce the imaginary but not the real part of the mechanical impedance of the organ of Corti, suggesting that the effective stiffness of outer hair cells (OHCs) is reduced by 9AC. To examine whether 9AC interacts directly with the motor protein prestin to reduce the membrane component of the impedance, the patch-clamp technique in whole-cell configuration was used to measure the nonlinear capacitance (NLC) of isolated OHCs and, as control, prestin-transfected human embryonic kidney 293 (HEK293) cells. Extracellular application of 9AC significantly reduced the NLC of both OHCs and HEK293 cells. Intracellular 9AC did not influence the blocking effect of the extracellular applied drug. These results suggest that 9AC interacts directly with prestin, reducing the effective stiffness of the motor, and that the interaction is extracellular.

Increasing the dynamic range of CMOS photodiode imagers

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor); Cunningham, Thomas J. (Inventor); Hancock, Bruce R. (Inventor)

2007-01-01

A multiple-step reset process and circuit for resetting a voltage stored on a photodiode of an imaging device. A first stage of the reset occurs while a source and a drain of a pixel source-follower transistor are held at ground potential and the photodiode and a gate of the pixel source-follower transistor are charged to an initial reset voltage having potential less that of a supply voltage. A second stage of the reset occurs after the initial reset voltage is stored on the photodiode and the gate of the pixel source-follower transistor and the source and drain voltages of the pixel source-follower transistor are released from ground potential thereby allowing the source and drain voltages of the pixel source-follower transistor to assume ordinary values above ground potential and resulting in a capacitive feed-through effect that increases the voltage on the photodiode to a value greater than the initial reset voltage.

Large Volume Non-Equilibrium Air Plasma at Atmospheric Pressure: A Novel Method with Low Power Requirements

DTIC Science & Technology

2007-02-28

of magnitude in size. Also unlike corona -like devices such as the plasma needle , which generates 2-3 mm long plasma at the tip of a sharp wire...Distribution Unlimited Table of Contents Abstract AC System with Water Electrode Current voltage characteristics Plasma diagnostics results Experimental setup...Laroussi, PI. 4 AC SYSTEM WITH WATER ELECTRODE Recently, non-equilibrium atmospheric pressure plasmas have been used in a variety of material processing

Multiple piezo-patch energy harvesters integrated to a thin plate with AC-DC conversion: analytical modeling and numerical validation

NASA Astrophysics Data System (ADS)

Aghakhani, Amirreza; Basdogan, Ipek; Erturk, Alper

2016-04-01

Plate-like components are widely used in numerous automotive, marine, and aerospace applications where they can be employed as host structures for vibration based energy harvesting. Piezoelectric patch harvesters can be easily attached to these structures to convert the vibrational energy to the electrical energy. Power output investigations of these harvesters require accurate models for energy harvesting performance evaluation and optimization. Equivalent circuit modeling of the cantilever-based vibration energy harvesters for estimation of electrical response has been proposed in recent years. However, equivalent circuit formulation and analytical modeling of multiple piezo-patch energy harvesters integrated to thin plates including nonlinear circuits has not been studied. In this study, equivalent circuit model of multiple parallel piezoelectric patch harvesters together with a resistive load is built in electronic circuit simulation software SPICE and voltage frequency response functions (FRFs) are validated using the analytical distributedparameter model. Analytical formulation of the piezoelectric patches in parallel configuration for the DC voltage output is derived while the patches are connected to a standard AC-DC circuit. The analytic model is based on the equivalent load impedance approach for piezoelectric capacitance and AC-DC circuit elements. The analytic results are validated numerically via SPICE simulations. Finally, DC power outputs of the harvesters are computed and compared with the peak power amplitudes in the AC output case.

Performance analysis of a diesel engine driven brushless alternator with combined AC and thyristor fed DC loads through PSPICE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narayanan, S.S.Y.; Ananthakrishnan, P.; Hangari, V.U.

1995-12-31

A brushless alternator with damper windings in the main alternator and with combined ac and thyristor fed dc loads has been handled ab initio as a total modeling and simulation problem for which a complete steady state performance prediction algorithm has been developed through proper application of Park`s equivalent circuit approach individually to the main and exciter alternator units of the brushless alternator. Details of the problems faced during implementation of this algorithm through PSPICE for the case of a specific 125 kVA brushless alternator as well as methods adopted for successfully overcoming the same have then been presented. Finallymore » a comparison of the predicted performance with those obtained experimentally for this 125 kVA unit has also been provided for the cases of both thyristor fed dc load alone as well as combined ac and thyristor fed dc loads. To enable proper calculation of derating factors to be used in the design of such brushless alternators, the simulation results then include harmonic analysis of the alternator output voltage and current waveforms at the point of common connection of the ac and thyristor fed dc load, damper winding currents, main alternator field winding current, exciter alternator armature voltage and the alternator developed torque and torque angle pulsations.« less

Power conversion apparatus and method

DOEpatents

Su, Gui-Jia [Knoxville, TN

2012-02-07

A power conversion apparatus includes an interfacing circuit that enables a current source inverter to operate from a voltage energy storage device (voltage source), such as a battery, ultracapacitor or fuel cell. The interfacing circuit, also referred to as a voltage-to-current converter, transforms the voltage source into a current source that feeds a DC current to a current source inverter. The voltage-to-current converter also provides means for controlling and maintaining a constant DC bus current that supplies the current source inverter. The voltage-to-current converter also enables the current source inverter to charge the voltage energy storage device, such as during dynamic braking of a hybrid electric vehicle, without the need of reversing the direction of the DC bus current.

Network-Cognizant Voltage Droop Control for Distribution Grids

DOE PAGES

Baker, Kyri; Bernstein, Andrey; Dall'Anese, Emiliano; ...

2017-08-07

Our paper examines distribution systems with a high integration of distributed energy resources (DERs) and addresses the design of local control methods for real-time voltage regulation. Particularly, the paper focuses on proportional control strategies where the active and reactive output-powers of DERs are adjusted in response to (and proportionally to) local changes in voltage levels. The design of the voltage-active power and voltage-reactive power characteristics leverages suitable linear approximation of the AC power-flow equations and is network-cognizant; that is, the coefficients of the controllers embed information on the location of the DERs and forecasted non-controllable loads/injections and, consequently, on themore » effect of DER power adjustments on the overall voltage profile. We pursued a robust approach to cope with uncertainty in the forecasted non-controllable loads/power injections. Stability of the proposed local controllers is analytically assessed and numerically corroborated.« less

Network-Cognizant Voltage Droop Control for Distribution Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Kyri; Bernstein, Andrey; Dall'Anese, Emiliano

Our paper examines distribution systems with a high integration of distributed energy resources (DERs) and addresses the design of local control methods for real-time voltage regulation. Particularly, the paper focuses on proportional control strategies where the active and reactive output-powers of DERs are adjusted in response to (and proportionally to) local changes in voltage levels. The design of the voltage-active power and voltage-reactive power characteristics leverages suitable linear approximation of the AC power-flow equations and is network-cognizant; that is, the coefficients of the controllers embed information on the location of the DERs and forecasted non-controllable loads/injections and, consequently, on themore » effect of DER power adjustments on the overall voltage profile. We pursued a robust approach to cope with uncertainty in the forecasted non-controllable loads/power injections. Stability of the proposed local controllers is analytically assessed and numerically corroborated.« less

Design considerations for large space electric power systems

NASA Technical Reports Server (NTRS)

Renz, D. D.; Finke, R. C.; Stevens, N. J.; Triner, J. E.; Hansen, I. G.

1983-01-01

As power levels of spacecraft rise to the 50 to 100 kW range, it becomes apparent that low voltage (28 V) dc power distribution and management systems will not operate efficiently at these higher power levels. The concept of transforming a solar array voltage at 150 V dc into a 1000 V ac distribution system operating at 20 kHz is examined. The transformation is accomplished with series-resonant inverter by using a rotary transformer to isolate the solar array from the spacecraft. The power can then be distributed in any desired method such as three phase delta to delta. The distribution voltage can be easily transformed to any desired load voltage and operating frequency. The reasons for the voltage limitations on the solar array due to plasma interactions and the many advantages of a high voltage, high frequency at distribution system are discussed.

Systems and methods for providing power to a load based upon a control strategy

DOEpatents

Perisic, Milun; Lawrence, Christopher P; Ransom, Ray M; Kajouke, Lateef A

2014-11-04

Systems and methods are provided for an electrical system. The electrical system, for example, includes a first load, an interface configured to receive a voltage from a voltage source, and a controller configured to receive the voltage through the interface and to provide a voltage and current to the first load. The controller may be further configured to, receive information on a second load electrically connected to the voltage source, determine an amount of reactive current to return to the voltage source such that a current drawn by the electrical system and the second load from the voltage source is substantially real, and provide the determined reactive current to the voltage source.

ac-driven vortices and the Hall effect in a superconductor with a tilted washboard pinning potential

NASA Astrophysics Data System (ADS)

Shklovskij, Valerij A.; Dobrovolskiy, Oleksandr V.

2008-09-01

The Langevin equation for a two-dimensional (2D) nonlinear guided vortex motion in a tilted cosine pinning potential in the presence of an ac is exactly solved in terms of a matrix continued fraction at arbitrary value of the Hall effect. The influence of an ac of arbitrary amplitude and frequency on the dc and ac magnetoresistivity tensors is analyzed. The ac density and frequency dependence of the overall shape and the number and position of the Shapiro steps on the anisotropic current-voltage characteristics are considered. The influence of a subcritical or overcritical dc on the time-dependent stationary ac longitudinal and transverse resistive vortex responses (on the frequency of an ac drive Ω ) in terms of the nonlinear impedance tensor Ẑ and the nonlinear ac response at Ω harmonics are studied. Analytical formulas for 2D temperature-dependent linear impedance tensor ẐL in the presence of a dc which depend on the angle α between the current-density vector and the guiding direction of the washboard planar pinning potential are derived and analyzed. Influence of α anisotropy and the Hall effect on the nonlinear power absorption by vortices is discussed.

Effects of voltage control in utility interactive dispersed storage and generation systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirkham, H.; Das, R.

1983-03-15

When a small generator is connected to the distribution system, the voltage at the point of interconnection is determined largely by the system and not the generator. This report examines the effect on the generator, on the load voltage and on the distribution system of a number of different voltage control strategies in the generator. Synchronous generators with three kinds of exciter control are considered, as well as induction generators and dc/ac inverters, with and without capacitor compensation. The effect of varying input power during operation (which may be experienced by generators based on renewable resources) is explored, as wellmore » as the effect of connecting and disconnecting the generator at ten percent of its rated power.« less

Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat; Plasma Technology and Nuclear Fusion Research Unit, Chulalongkorn University, Bangkok

2015-04-24

Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (T{sub e}) and electron number density (n{sub e}) canmore » be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10{sup −17} − 10{sup −18} m{sup −3} where the electron temperature is between 1.00−2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.« less

Series resonance inverter with triggered vacuum gaps

NASA Astrophysics Data System (ADS)

Damstra, Geert C.; Zhang, X.

1994-05-01

Series resonance inverters based on semi-conductor switching elements are well-known and have a wide range of application, mainly for lower voltages. For high voltage application many switching elements have to be put in series to obtain sufficient blocking voltage. Voltage grinding and multiple gate control elements are needed. There is much experience with the triggered vacuum gaps as high voltage/high current single shot elements, for example in reignition circuits for synthetic circuit breaker tests. These elements have a blocking voltage of 50 - 100 kV and are triggerable by a light fiber control device. A prototype inverter has been developed that generates 0.1 Hz, 30 kV AC voltages with a flat top for tests on cables and capacitors of many micro farads fed from a low voltage supply of about 600 V. Only two TVG elements are needed to switch the resonant circuit alternatively on the positive or negative supply. The resonant circuit itself consists of the capacitance of the testobject and a high quality inductor that determines the frequency and the peak current of the voltage reversing process.

Charge-pump voltage converter

DOEpatents

Brainard, John P [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM

2009-11-03

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Time varying voltage combustion control and diagnostics sensor

DOEpatents

Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy D [Morgantown, WV; Huckaby, E David [Morgantown, WV; Fincham, William [Fairmont, WV

2011-04-19

A time-varying voltage is applied to an electrode, or a pair of electrodes, of a sensor installed in a fuel nozzle disposed adjacent the combustion zone of a continuous combustion system, such as of the gas turbine engine type. The time-varying voltage induces a time-varying current in the flame which is measured and used to determine flame capacitance using AC electrical circuit analysis. Flame capacitance is used to accurately determine the position of the flame from the sensor and the fuel/air ratio. The fuel and/or air flow rate (s) is/are then adjusted to provide reduced flame instability problems such as flashback, combustion dynamics and lean blowout, as well as reduced emissions. The time-varying voltage may be an alternating voltage and the time-varying current may be an alternating current.

Laser beam apparatus and method for analyzing solar cells

DOEpatents

Staebler, David L.

1980-01-01

A laser beam apparatus and method for analyzing, inter alia, the current versus voltage curve at the point of illumination on a solar cell and the open circuit voltage of a solar cell. The apparatus incorporates a lock-in amplifier, and a laser beam light chopper which permits the measurement of the AC current of the solar cell at an applied DC voltage at the position on the solar cell where the cell is illuminated and a feedback scheme which permits the direct scanning measurements of the open circuit voltage. The accuracy of the measurement is a function of the intensity and wavelength of the laser light with respect to the intensity and wavelength distribution of sunlight and the percentage the dark current is at the open circuit voltage to the short circuit current of the solar cell.

Note: A phase synchronization photography method for AC discharge.

PubMed

Wu, Zhicheng; Zhang, Qiaogen; Ma, Jingtan; Pang, Lei

2018-05-01

To research discharge physics under AC voltage, a phase synchronization photography method is presented. By using a permanent-magnet synchronous motor to drive a photography mask synchronized with a discharge power supply, discharge images in a specific phase window can be recorded. Some examples of discharges photographed by this method, including the corona discharge in SF 6 and the corona discharge along the air/epoxy surface, demonstrate the feasibility of this method. Therefore, this method provides an effective tool for discharge physics researchers.

Note: A phase synchronization photography method for AC discharge

NASA Astrophysics Data System (ADS)

Wu, Zhicheng; Zhang, Qiaogen; Ma, Jingtan; Pang, Lei

2018-05-01

To research discharge physics under AC voltage, a phase synchronization photography method is presented. By using a permanent-magnet synchronous motor to drive a photography mask synchronized with a discharge power supply, discharge images in a specific phase window can be recorded. Some examples of discharges photographed by this method, including the corona discharge in SF6 and the corona discharge along the air/epoxy surface, demonstrate the feasibility of this method. Therefore, this method provides an effective tool for discharge physics researchers.

Electrical and Biological Effects of Transmission Lines: A Review.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jack M.

1989-06-01

This review describes the electrical properties of a-c and d-c transmission lines and the resulting effects on plants, animals, and people. Methods used by BPA to mitigate undesirable effects are also discussed. Although much of the information in this review pertains to high-voltage transmission lines, information on distribution lines and electrical appliances is included. The electrical properties discussed are electric and magnetic fields and corona: first for alternating-current (a-c) lines, then for direct current (d-c).

Program Predicts Nonlinear Inverter Performance

NASA Technical Reports Server (NTRS)

Al-Ayoubi, R. R.; Oepomo, T. S.

1985-01-01

Program developed for ac power distribution system on Shuttle orbiter predicts total load on inverters and node voltages at each of line replaceable units (LRU's). Mathematical model simulates inverter performance at each change of state in power distribution system.

Characterization of LiMn 2O 4 cathodes by electrochemical strain microscopy

DOE PAGES

Alikin, D. O.; Ievlev, A. V.; Luchkin, S. Yu.; ...

2016-03-15

Electrochemical strain microscopy (ESM) is a scanning probe microscopy(SPM) method in which the local electrodiffusion is probed via application of AC voltage to the SPM tip and registration of resulting electrochemical strain. In this study, we implemented ESM to measure local strain in bulk LiMn 2O 4 cathodes of a commercial Li-battery in different states of charge to investigate distribution of Li-ion mobility and concentration. Ramped AC ESM imaging and voltage spectroscopy were used to find the most reliable regime of measurements allowing separating and diminishing different contributions to ESM. This is not a trivial task due to complex geometrymore » of the sample and various obstacles resulting in less predictable contributions of different origins into ESM response: electrostatic tip–surface interactions, charge injection, electrostriction, and flexoelectricity. Finally, understanding and control of these contributions is an important step towards quantitative interpretation of ESM data.« less

Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wei, Xing; Sugri Nbelayim, Pascal; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2017-03-01

A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes.

PubMed

Wu, Xiaojian; Ramiah Rajasekaran, Pradeep; Martin, Charles R

2016-04-26

Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an electrokinetic phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps.

Lab-on-a-chip Single Particle Dielectrophoretic Traps

NASA Astrophysics Data System (ADS)

Wang, Weina; Shao, Hua; Lear, Kevin

2007-03-01

Cell-patterning and cell-manipulation in micro-environments are fundamental to biological and biomedical applications, for example, spectroscopic cytology based cancer detection. Dielectrophoresis (DEP) traps with transparent centers for stabilized cell and particle optofluidic intracavity spectroscopy (OFIS) were fabricated by patterning 10 μm wide, planar gold electrodes on glass substrates. The capturing strength of DEP traps was quantified based on the minimum AC voltage required to capture and hold varying diameter polystyrene or was it some other material, e.g. silica or PMMA microspheres in water as a function of frequency required under a constant flowrate of 20 μm/s. The maximum required trapping voltage in the negative DEP regime of f = 1 kHz to 40 MHz was 5.0 VAC. The use of AC fields effectively suppressed hydrolysis. New geometries of DEP traps are being explored on the basis of 3-D electrostatic field simulations.

Results of the harmonics measurement program at the John F. Long photovoltaic house

NASA Astrophysics Data System (ADS)

Campen, G. L.

1982-03-01

Photovoltaic (PV) systems used in single-family dwellings require an inverter to act as an interface between the direct-current (dc) power output of the PV unit and the alternating-current (ac) power needed by house loads. A type of inverter known as line commutated injects harmonic currents on the ac side and requires large amounts of reactive power. Large numbers of such PV installations could lead to unacceptable levels of harmonic voltages on the utility system, and the need to increase the utility's deliver of reactive power could result in significant cost increases. The harmonics and power-factor effects are examined for a single PV installation using a line-commutated inverter. The magnitude and phase of various currents and voltages from the fundamental to the 13th harmonic were recorded both with and without the operation of the PV system.

Tailoring particle translocation via dielectrophoresis in pore channels

PubMed Central

Tanaka, Shoji; Tsutsui, Makusu; Theodore, Hu; Yuhui, He; Arima, Akihide; Tsuji, Tetsuro; Doi, Kentaro; Kawano, Satoyuki; Taniguchi, Masateru; Kawai, Tomoji

2016-01-01

Understanding and controlling electrophoretic motions of nanoscopic objects in fluidic channels are a central challenge in developing nanopore technology for molecular analyses. Although progress has been made in slowing the translocation velocity to meet the requirement for electrical detections of analytes via picoampere current measurements, there exists no method useful for regulating particle flows in the transverse directions. Here, we report the use of dielectrophoresis to manipulate the single-particle passage through a solid-state pore. We created a trap field by applying AC voltage between electrodes embedded in a low-aspect-ratio micropore. We demonstrated a traffic control of particles to go through center or near side surface via the voltage frequency. We also found enhanced capture efficiency along with faster escaping speed of particles by virtue of the AC-mediated electroosmosis. This method is compatible with nanopore sensing and would be widely applied for reducing off-axis effects to achieve single-molecule identification. PMID:27527126

Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

NASA Technical Reports Server (NTRS)

Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

2016-01-01

The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid-electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid-electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of AC and DC for power transmission. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power generation, transmission, and distribution systems, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of dual-fed induction machines, which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the project along with the system architecture, development status and preliminary results.

Spectral response of atmospheric electric field measurements near AC high voltage power lines

NASA Astrophysics Data System (ADS)

Silva, H. G.; Matthews, J. C.; Wright, M. D.; Shallcross, D. E.

2015-10-01

To understand the influence of corona ion emission on the atmospheric electrical field, measurements were made near to two AC high voltage power lines. A JCI 131 field-mill recorded the atmospheric electric field over one year. Meteorological measurements were also taken. The data series is divided in four zones (dependent on wind direction): whole zones, Z0; zone 1, Z1; zone 2, Z2; zone 3, Z3. Z3 is the least affected by corona ion emission and for that reason it is used as a reference against Z1 and Z2, which are strongly influenced by this phenomena. Analysis was undertaken for all weather days and dry days only. The Lomb-Scargle strategy developed for unevenly spaced time-series is used to calculate the spectral response of the aforementioned zones. Only frequencies above 1 minute are considered.

ac Modeling and impedance spectrum tests of the superconducting magnetic field coils for the Wendelstein 7-X fusion experiment.

PubMed

Ehmler, Hartmut; Köppen, Matthias

2007-10-01

The impedance spectrum test was employed for detection of short circuits within Wendelstein 7-X (W7-X) superconducting magnetic field coils. This test is based on measuring the complex impedance over several decades of frequency. The results are compared to predictions of appropriate electrical equivalent circuits of coils in different production states or during cold test. When the equivalent circuit is not too complicated the impedance can be represented by an analytic function. A more detailed analysis is performed with a network simulation code. The overall agreement of measured and calculated or simulated spectra is good. Two types of short circuits which appeared are presented and analyzed. The detection limit of the method is discussed. It is concluded that combined high-voltage ac and low-voltage impedance spectrum tests are ideal means to rule out short circuits in the W7-X coils.

Possibilities and limitations of advanced transmission electron microscopy for carbon-based nanomaterials

PubMed Central

Bittencourt, Carla; Van Tendeloo, Gustaaf

2015-01-01

Summary A major revolution for electron microscopy in the past decade is the introduction of aberration correction, which enables one to increase both the spatial resolution and the energy resolution to the optical limit. Aberration correction has contributed significantly to the imaging at low operating voltages. This is crucial for carbon-based nanomaterials which are sensitive to electron irradiation. The research of carbon nanomaterials and nanohybrids, in particular the fundamental understanding of defects and interfaces, can now be carried out in unprecedented detail by aberration-corrected transmission electron microscopy (AC-TEM). This review discusses new possibilities and limits of AC-TEM at low voltage, including the structural imaging at atomic resolution, in three dimensions and spectroscopic investigation of chemistry and bonding. In situ TEM of carbon-based nanomaterials is discussed and illustrated through recent reports with particular emphasis on the underlying physics of interactions between electrons and carbon atoms. PMID:26425406

Evaluation of slim-edge, multi-guard, and punch-through-protection structures before and after proton irradiation

NASA Astrophysics Data System (ADS)

Mitsui, S.; Unno, Y.; Ikegami, Y.; Takubo, Y.; Terada, S.; Hara, K.; Takahashi, Y.; Jinnouchi, O.; Nagai, R.; Kishida, T.; Yorita, K.; Hanagaki, K.; Takashima, R.; Kamada, S.; Yamamura, K.

2013-01-01

Planar geometry silicon pixel and strip sensors for the high luminosity upgrade of the LHC (HL-LHC) require a high bias voltage of 1000 V in order to withstand a radiation damage caused by particle fluences of 1×1016 1 MeV neq/cm2 and 1×1015 1 MeV neq/cm2 for pixel and strip detectors, respectively. In order to minimize the inactive edge space that can withstand a bias voltage of 1000 V, edge regions susceptible to microdischarge (MD) should be carefully optimized. We fabricated diodes with various edge distances (slim-edge diodes) and with 1-3 multiple guard rings (multi-guard diodes). AC coupling insulators of strip sensors are vulnerable to sudden heavy charge deposition, such as an accidental beam splash, which may destroy the readout AC capacitors. Thus various types of punch-through-protection (PTP) structures were implemented in order to find the most effective structure to protect against heavy charge deposition. These samples were irradiated with 70 MeV protons at fluences of 5×1012 1 MeV neq/cm2-1×1016 1 MeV neq/cm2. Their performances were evaluated before and after irradiation in terms of an onset voltage of the MD, a turn-on voltage of the PTP, and PTP saturation resistance.

Over-current carrying characteristics of rectangular-shaped YBCO thin films prepared by MOD method

NASA Astrophysics Data System (ADS)

Hotta, N.; Yokomizu, Y.; Iioka, D.; Matsumura, T.; Kumagai, T.; Yamasaki, H.; Shibuya, M.; Nitta, T.

2008-02-01

A fault current limiter (FCL) may be manufactured at competitive qualities and prices by using rectangular-shaped YBCO films which are prepared by metal-organic deposition (MOD) method, because the MOD method can produce large size elements with a low-cost and non-vacuum technique. Prior to constructing a superconducting FCL (SFCL), AC over-current carrying experiments were conducted for 120 mm long elements where YBCO thin film of about 200 nm in thickness was coated on sapphire substrate with cerium oxide (CeO2) interlayer. In the experiments, only single cycle of the ac damping current of 50 Hz was applied to the pure YBCO element without protective metal coating or parallel resistor and the magnitude of the current was increased step by step until the breakdown phenomena occurred in the element. In each experiment, current waveforms flowing through the YBCO element and voltage waveform across the element were measured to get the voltage-current characteristics. The allowable over-current and generated voltage were successfully estimated for the pure YBCO films. It can be pointed out that the lower n-value trends to bring about the higher allowable over-current and the higher withstand voltage more than tens of volts. The YBCO film having higher n-value is sensitive to the over-current. Thus, some protective methods such as a metal coating should be employed for applying to the fault current limiter.

Producing fluid flow using 3D carbon electrodes

NASA Astrophysics Data System (ADS)

Rouabah, H. A.; Park, B. Y.; Zaouk, R. B.; Madou, M. J.; Green, Nicolas G.

2008-12-01

Moving and manipulating bio-particles and fluids on the microscale is central to many lab-on-a-chip applications. Techniques for pumping fluids which use electric fields have shown promise using both DC and AC voltages. AC techniques, however, require the use of integrated metal electrodes which have a low resistance but can suffer from unwanted chemical reactions even at low potentials. In this paper we introduce the use of carbon MEMS technology (C-MEMS), a fabrication method which produces 3D conductive polymeric structures. Results are presented of the fabrication of an innovative design of 3D AC-electroosmotic micropump and preliminary experimental measurements which demonstrate the potential of both the technology and the design.

High voltage AC plasma torches with long electric arcs for plasma-chemical applications

NASA Astrophysics Data System (ADS)

Surov, A. V.; Popov, S. D.; Serba, E. O.; Pavlov, A. V.; Nakonechny, Gh V.; Spodobin, V. A.; Nikonov, A. V.; Subbotin, D. I.; Borovskoy, A. M.

2017-04-01

Powerful AC plasma torches are in demand for a number of advanced plasma chemical applications, they can provide high enthalpy of the working gas. IEE RAS specialists have developed a number of models of stationary thermal plasma torches for continuous operation on air with the power from 5 to 500 kW, and on mixture of H2O, CO2 and CH4 up to 150 kW. AC plasma torches were tested on the pilot plasmachemical installations. Powerful AC plasma torch with hollow electrodes and the gas vortex stabilization of arc in cylindrical channels and its operation characteristics are presented. Lifetime of its continuous operation on air is 2000 hours and thermal efficiency is about 92%, the electric arc length between two electrodes of the plasma torch exceeds 2 m.

Restraining for switching effects in an AC driving pixel circuit of the OLED-on-silicon

NASA Astrophysics Data System (ADS)

Liu, Yan-Yan; Geng, Wei-Dong; Dai, Yong-Ping

2010-03-01

The AC driving scheme for OLEDs, which uses the pixel circuit with two transistors and one capacitor (2T1C), can extend the lifetime of the active matrix organic light-emitting diode (AMOLED) on silicon, but there are switching effects during the switch of AC signals, which result in the voltage variation on the storage capacitor and cause the current glitch in OLED. That would decrease the gray scale of the OLED. This paper proposes a novel pixel circuit consisting of three transistors and one capacitor to realize AC driving for the OLED-on-silicon while restraining the switching effects. Simulation results indicate that the proposed circuit is less sensitive to switching effects. Also, another pixel circuit is proposed to further reduce the driving current to meet the current constraints for the OLED-on-silicon.

Improved frequency/voltage converters for fast quartz crystal microbalance applications.

PubMed

Torres, R; García, J V; Arnau, A; Perrot, H; Kim, L To Thi; Gabrielli, C

2008-04-01

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mVHz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

A Method for Growing Bio-memristors from Slime Mold.

PubMed

Miranda, Eduardo Reck; Braund, Edward

2017-11-02

Our research is aimed at gaining a better understanding of the electronic properties of organisms in order to engineer novel bioelectronic systems and computing architectures based on biology. This specific paper focuses on harnessing the unicellular slime mold Physarum polycephalum to develop bio-memristors (or biological memristors) and bio-computing devices. The memristor is a resistor that possesses memory. It is the 4th fundamental passive circuit element (the other three are the resistor, the capacitor, and the inductor), which is paving the way for the design of new kinds of computing systems; e.g., computers that might relinquish the distinction between storage and a central processing unit. When applied with an AC voltage, the current vs. voltage characteristic of a memristor is a pinched hysteresis loop. It has been shown that P. polycephalum produces pinched hysteresis loops under AC voltages and displays adaptive behavior that is comparable with the functioning of a memristor. This paper presents the method that we developed for implementing bio-memristors with P. polycephalum and introduces the development of a receptacle to culture the organism, which facilitates its deployment as an electronic circuit component. Our method has proven to decrease growth time, increase component lifespan, and standardize electrical observations.

Comparative analysis of approaches to frequency measurement and power estimation for polyharmonic microwave signals on the basis of the ac Josephson effect

NASA Astrophysics Data System (ADS)

Larkin, Serguey Y.; Anischenko, Serguei E.; Kamyshin, Vladimir A.

1996-12-01

The frequency and power measurements technique using ac Josephson effect is founded on deviation of the voltagecurrent curve of irradiated Josephson junction from its autonomous voltage-current (V-I) curve [1]. Generally this technique, in case of harmonic incident radiation, may be characterized in the following manner: -to measure frequency of the hannonic microwave signal inadiating the Josephson junction and to estimate its intensity using functional processing of the voltage-current curves, one should identify the "Special feature existence" zone on the voltage-current curves. The "Special feature existence" zone results the junction's response to the incident radiation. As this takes place, it is necessary to define the coordinate of a central point of the "Special feature existence" zone on the curve and to estimate the deviation of the V-I curve of irradiated Josephson junction from its autonomous V-I curve. The practical implementation of this technique place at one's disposal a number of algorithms, which enable to realize frequency measurements and intensity estimation with a particular accuracy for incident radiation. This paper presents two rational algorithms to determine the aggregate of their merits and disadvantages and to choose more optimal one.

Development of external cooling cryo-resistive cable systems. Part 2: Insulation characteristics on 66 kV rated cryo-resistive testing cable

NASA Astrophysics Data System (ADS)

Ishihara, Kaoru; Akita, Shige; Suzuki, Hiroshi; Ogata, Junichi; Nemoto, Minoru

1987-08-01

Cryo-resistive cable system was tested to demonstrate dielectric characteristics. Dielectric characteristics of 66kV cryo-resistive cable at the start of immersion cooling in the liquid nitrogen were 2.25 specific dielectric constant and 0.18 percent dielectric loss which was less than 0.4 percent , the aimed value. Electrostatic capacity and dielectric loss tangent of dielectric characteristics under the applied voltage did not depend on the voltage and the dielectric loss was less than 0.4 percent through the temperature range from -170 to -190C. These values fulfilled the specifications on 275kV class cryo-resistive cable design. The tested cable passed the cable test on 66kV oil-filled cable (ac 90kV, 10 min), but broken down at ac 110kV on the way to endurance testing voltage 130kV. The breakdown occurred due to the mechanical damage of cable insulator by bending and thermal contraction of the cable. It is necessary from these facts to develop flexible cable terminal and joint which can absorb the contraction to realize 275kV cryo-resistive cable. (19 figs, 7 tabs, 15 refs).

Improved frequency/voltage converters for fast quartz crystal microbalance applications

NASA Astrophysics Data System (ADS)

Torres, R.; García, J. V.; Arnau, A.; Perrot, H.; Kim, L. To Thi; Gabrielli, C.

2008-04-01

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10mV/Hz, for a frequency shift resolution of 0.1Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5to10MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

Investigation of voltage source design's for Electrical Impedance Mammography (EIM) Systems.

PubMed

Qureshi, Tabassum R; Chatwin, Chris R; Zhou, Zhou; Li, Nan; Wang, W

2012-01-01

According to Jossient, interesting characteristics of breast tissues mostly lie above 1MHz; therefore a wideband excitation source covering higher frequencies (i.e. above 1MHz) is required. The main objective of this research is to establish a feasible bandwidth envelope that can be used to design a constant EIM voltage source over a wide bandwidth with low output impedance for practical implementation. An excitation source is one of the major components in bio-impedance measurement systems. In any bio-impedance measurement system the excitation source can be achieved either by injecting current and measuring the resulting voltages, or by applying voltages and measuring the current developed. This paper describes three voltage source architectures and based on their bandwidth comparison; a differential voltage controlled voltage source (VCVS) is proposed, which can be used over a wide bandwidth (>15MHz). This paper describes the performance of the designed EIM voltage source for different load conditions and load capacitances reporting signal-to-noise ratio of approx 90dB at 10MHz frequency, signal phase and maximum of 4.75kΩ source output impedance at 10MHz. Optimum data obtained using Pspice® is used to demonstrate the high-bandwidth performance of the source.

Ion Current Rectification, Limiting and Overlimiting Conductances in Nanopores

PubMed Central

van Oeffelen, Liesbeth; Van Roy, Willem; Idrissi, Hosni; Charlier, Daniel; Lagae, Liesbet; Borghs, Gustaaf

2015-01-01

Previous reports on Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores have focused on steady state behaviour under simplified boundary conditions. These are Neumann boundary conditions for the voltage at the pore walls, and in some cases also Donnan equilibrium boundary conditions for concentrations and voltages at both entrances of the nanopore. In this paper, we report time-dependent and steady state PNP simulations under less restrictive boundary conditions, including Neumann boundary conditions applied throughout the membrane relatively far away from the nanopore. We simulated ion currents through cylindrical and conical nanopores with several surface charge configurations, studying the spatial and temporal dependence of the currents contributed by each ion species. This revealed that, due to slow co-diffusion of oppositely charged ions, steady state is generally not reached in simulations or in practice. Furthermore, it is shown that ion concentration polarization is responsible for the observed limiting conductances and ion current rectification in nanopores with asymmetric surface charges or shapes. Hence, after more than a decade of collective research attempting to understand the nature of ion current rectification in solid-state nanopores, a relatively intuitive model is retrieved. Moreover, we measured and simulated current-voltage characteristics of rectifying silicon nitride nanopores presenting overlimiting conductances. The similarity between measurement and simulation shows that overlimiting conductances can result from the increased conductance of the electric double-layer at the membrane surface at the depletion side due to voltage-induced polarization charges. The MATLAB source code of the simulation software is available via the website http://micr.vub.ac.be. PMID:25978328

Density-matrix renormalization group method for the conductance of one-dimensional correlated systems using the Kubo formula

NASA Astrophysics Data System (ADS)

Bischoff, Jan-Moritz; Jeckelmann, Eric

2017-11-01

We improve the density-matrix renormalization group (DMRG) evaluation of the Kubo formula for the zero-temperature linear conductance of one-dimensional correlated systems. The dynamical DMRG is used to compute the linear response of a finite system to an applied ac source-drain voltage; then the low-frequency finite-system response is extrapolated to the thermodynamic limit to obtain the dc conductance of an infinite system. The method is demonstrated on the one-dimensional spinless fermion model at half filling. Our method is able to replicate several predictions of the Luttinger liquid theory such as the renormalization of the conductance in a homogeneous conductor, the universal effects of a single barrier, and the resonant tunneling through a double barrier.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air.

PubMed

Jain, Vishal; Visani, Anand; Srinivasan, R; Agarwal, Vivek

2018-03-01

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (∼0.28 W/cm 2 ) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (∼50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air

NASA Astrophysics Data System (ADS)

Jain, Vishal; Visani, Anand; Srinivasan, R.; Agarwal, Vivek

2018-03-01

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (˜0.28 W/cm2) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (˜50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites.

PubMed

Sreenivasulu, Gollapudi; Qu, Peng; Petrov, Vladimir; Qu, Hongwei; Srinivasan, Gopalan

2016-02-20

Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data.

A linearly controlled direct-current power source for high-current inductive loads in a magnetic suspension wind tunnel

NASA Technical Reports Server (NTRS)

Tripp, John S.; Daniels, Taumi S.

1990-01-01

The NASA Langley 6 inch magnetic suspension and balance system (MSBS) requires an independently controlled bidirectional DC power source for each of six positioning electromagnets. These electromagnets provide five-degree-of-freedom control over a suspended aerodynamic test model. Existing power equipment, which employs resistance coupled thyratron controlled rectifiers as well as AC to DC motor generator converters, is obsolete, inefficient, and unreliable. A replacement six phase bidirectional controlled bridge rectifier is proposed, which employs power MOSFET switches sequenced by hybrid analog/digital circuits. Full load efficiency is 80 percent compared to 25 percent for the resistance coupled thyratron system. Current feedback provides high control linearity, adjustable current limiting, and current overload protection. A quenching circuit suppresses inductive voltage impulses. It is shown that 20 kHz interference from positioning magnet power into MSBS electromagnetic model position sensors results predominantly from capacitively coupled electric fields. Hence, proper shielding and grounding techniques are necessary. Inductively coupled magnetic interference is negligible.

AC power generation from microbial fuel cells

NASA Astrophysics Data System (ADS)

Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

2015-11-01

Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

Measurements and calculations of transport AC loss in second generation high temperature superconducting pancake coils

NASA Astrophysics Data System (ADS)

Yuan, Weijia; Coombs, T. A.; Kim, Jae-Ho; Han Kim, Chul; Kvitkovic, Jozef; Pamidi, Sastry

2011-12-01

Theoretical and experimental AC loss data on a superconducting pancake coil wound using second generation (2 G) conductors are presented. An anisotropic critical state model is used to calculate critical current and the AC losses of a superconducting pancake coil. In the coil there are two regions, the critical state region and the subcritical region. The model assumes that in the subcritical region the flux lines are parallel to the tape wide face. AC losses of the superconducting pancake coil are calculated using this model. Both calorimetric and electrical techniques were used to measure AC losses in the coil. The calorimetric method is based on measuring the boil-off rate of liquid nitrogen. The electric method used a compensation circuit to eliminate the inductive component to measure the loss voltage of the coil. The experimental results are consistent with the theoretical calculations thus validating the anisotropic critical state model for loss estimations in the superconducting pancake coil.

VISUAL ALARM SYSTEM

DOEpatents

Morris, J.M.

1958-11-01

A vlsual alarm system, particularly a system incorporating a gas-fllled diode glow bulb, for indicating a minor alarm and also a major alarm is presented. In operation, the disclosed system responds to a signal indlcative of a caution condition by applying a d-c voltage across the glow bulb to induce a glow at one electrode. If a signal indicative of a critlcal condition is received, the system applies an a-c voltage across tbe glow bulb to produce a glow discharge at each electrode.

Effects of voltage control in utility interactive dispersed storage and generation systems

NASA Technical Reports Server (NTRS)

Kirkham, H.; Das, R.

1983-01-01

When a small generator is connected to the distribution system, the voltage at the point of interconnection is determined largely by the system and not the generator. The effect on the generator, on the load voltage and on the distribution system of a number of different voltage control strategies in the generator is examined. Synchronous generators with three kinds of exciter control are considered, as well as induction generators and dc/ac inverters, with and without capacitor compensation. The effect of varying input power during operation (which may be experienced by generators based on renewable resources) is explored, as well as the effect of connecting and disconnecting the generator at ten percent of its rated power. Operation with a constant slightly lagging factor is shown to have some advantages.

MAGNETOMETER

DOEpatents

Leavitt, M.A.

1958-11-18

A magnetometer ls described, partlcularly to a device which accurately indicates the polarity and intensity of a magnetlc field. The main feature of the invention is a unique probe construction in combinatlon wlth a magnetic fleld detector system. The probe comprises two coils connected in series opposition for energization with an a-c voltage. The voltage lnduced in a third coll on the probe, a pick-up coil, is distorted by the presence of an external field to produce even harmonic voltages. A controlled d-c current is passed through the energized coils to counter the dlstortlon and reduce tbe even harmonic content to a null. When the null point is reached, the d-c current is a measure of the external magnetic field strength, and the phase of the pickup coil voltage indicates tbe field polarlty.