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1

DC wiring system grounding and ground fault protection issues for central station photovoltaic power plants  

NASA Technical Reports Server (NTRS)

The DC wiring system for a photovoltaic power plant presents a number of unique challenges to be overcome by the plant designers. There are a number of different configurations that the grounding of the DC wiring system can take, and the choice will affect the number and type of protective devices required to ensure safety of personnel and protection of equipment. The major grounding and fault protection considerations that must be taken into account when selecting the basic overall circuit configuration are summarized. The inherent advantages and disadvantages of each type of circuit grounding (resistance or solid) along with the personnel safety and equipment protection issues for each of these grounding methods are presented.

Simburger, E. J.

1983-01-01

2

EXPERIMENTS WITH A DC WIRE IN RHIC  

SciTech Connect

A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.

FISCHER,W.; CALAGA, R.; DORDA, U.; KOUTCHOUK, J.-P.; ZIMMERMANN, F.; SEN, T.

2007-06-25

3

Experiments with a DC wire in RHIC.  

National Technical Information Service (NTIS)

A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanyin...

A. Kabel, F. Zimmerman, G. Robert-Demolaize, H. J. Kim, J. Qiang, J. P. Koutchouk, N. Abreu, R. Calaga, T. Sen, U. Dorda, W. Fischer

2007-01-01

4

Topology for Current Balancer with Half-Bridge Inverters in Single-Phase Three-Wire Distribution Systems with DC-Capacitor-Voltage Balancer  

NASA Astrophysics Data System (ADS)

This paper proposes a new topology for a current balancer with half-bridge inverters in single-phase three-wire distribution systems with a three-leg inverter. Two half-bridge inverters are connected to the sources. The midpoint of two capacitors on the DC-side is connected to a neutral line. The two half-bridge inverters perform a current balancer for single-phase three-wire distribution systems by exchanging the active and reactive power on the each feeder through the two DC-capacitors. The third-leg performs a DC-capacitor-voltage balancer for the two DC-capacitors connected to the half-bridge inverters. Thus, balanced source voltages and currents are obtained on the secondary-side on the pole-mounted distribution transformer with balanced DC-capacitor voltages. The basic principle of the proposed current balancer is discussed in detail, and then, confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results show that balanced source voltages and currents are obtained on the secondary-side on the pole-mounted distribution transformer with balanced DC-capacitor voltages.

Baba, Yusuke; Sugahara, Kazuya; Okamoto, Masayuki; Hiraki, Eiji; Tanaka, Toshihiko

5

A Constant DC Voltage Control Based Strategy for the Current Balancer in Single-Phase Three-Wire Secondary Distribution Systems  

NASA Astrophysics Data System (ADS)

This paper deals with applying the constant dc voltage control based algorithm to the current balancer in single-phase three-wire secondary distribution systems. The power flows into a three-leg inverter, which performs the current balancer, are discussed, and then we show that only the reactive power flows into the three-leg inverter. This demonstrates that the required-capacity of the dc capacitor can be reduced as compared to that of the active power quality compensator used in the electrified railways. This reduced-capacity dc capacitor results in the rapid and stable balancing. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the balanced source currents with unity power factor are obtained remaining the unbalanced load currents conditions.

Fukui, Hirokazu; Hiraki, Eiji; Tanaka, Toshihiko

6

A Constant DC-Capacitor Voltage Control Based Strategy for Current Balancer in Single-Phase Three-Wire Distribution Systems  

NASA Astrophysics Data System (ADS)

This paper proposes a strategy based on constant dc-capacitor voltage control for a current balancer in single-phase three-wire distribution systems. The proposed control strategy involves the use of only the constant dc-capacitor voltage control block commonly used in active power conditioners for the calculation of the compensation current. No calculation block is required to obtain the reactive and unbalanced-active components. Thus, we provide the simplest possible control strategy for the current balancer. The basic principle of the proposed control method is discussed in detail and its validity, which is confirmed by a digital computer simulation using PSIM software, is shown. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of unity are obtained on the secondary side of a pole-mounted distribution transformer while unbalanced load current conditions with a lagging power factor are retained.

Baba, Yusuke; Okamoto, Masayuki; Hiraki, Eiji; Tanaka, Toshihiko; Lee, Seong Ryong

7

A novel four-branches-inverter-based-active-filter for harmonic suppression and reactive compensation of an unbalanced three-phase four-wires electrical distribution systems, feeding AC\\/DC loads  

Microsoft Academic Search

This paper deals with the design, analysis and digital simulation of a novel four-branches-inverter-based-active-filter, that compensates the reactive power and suppress the harmonic currents in the phases and neutral of an unbalanced three-phase four-wires electrical distribution system, feeding AC\\/DC loads. That is, the filter has the capability to instantaneously suppress the harmonics currents, in both the three-phases and the neutral,

Alfredo Nava-Segura; G. Mino-Aguilar

2000-01-01

8

LANSCE-R WIRE-SCANNER SYSTEM  

SciTech Connect

The National Instruments cRIO platform is used for the new LANSCE-R wire-scanner systems. All wire-scanner electronics are integrated into a single BiRa BiRIO 4U cRIO chassis specifically designed for the cRIO crate and all interface electronics. The BiRIO chassis, actuator and LabVIEW VIs provide a complete wire-scanner system integrated with EPICS. The new wire-scanner chassis includes an 8-slot cRIO crate with Virtex-5 LX 110 FPGA and Power-PC real-time controller, the LANL-developed cRIO 2-axis wire-sensor analog interface module (AFE), NI9222 cRIO 4-channel 16-bit digitizer, cRIO resolver demodulator, cRIO event receiver, front-panel touch panel display, motor driver, and all necessary software, interface wiring, connectors and ancillary components. This wirescanner system provides a complete, turn-key, 2-axis wire-scanner system including 2-channel low-noise sensewire interface with variable DC wire bias and wireintegrity monitor, 16-bit signal digitizers, actuator motor drive and control, actuator position sensing, limit-switch interfaces, event receiver, LabVIEW and EPICS interface, and both remote operation and full stand-alone operation using the touch panel.

Gruchalla, Michael E. [Los Alamos National Laboratory

2011-01-01

9

A 37 channel DC SQUID magnetometer system  

Microsoft Academic Search

A 37-channel DC SQUID magnetometer system has been built for biomagnetic studies. The SQUID loop of each magnetometer serves as the active sensing element, thereby eliminating the need for flux coupling circuits. The magnetometers are located ≃3 cm above the outer dewar bottom. The SQUIDs are directly coupled to a highly simplified readout electronics using only five wires per channel;

H. Koch; R. Cantor; D. Drung; S. N. Erne; K. P. Matthies; M. Peters; T. Ryhanen; H. J. Scheer; H. D. Hahlbohm

1991-01-01

10

Gold wire stress analysis of wire feed system in automatic wire bonder  

Microsoft Academic Search

The wire feed system is an important subsystem of typical automatic wire bonder. The resistance control of wire transmission and tensile force control are the key technologies of the wire feed system, which has a strong impact on the bonding quality. This paper describes the stress analysis of gold wire in the automatic wire bonder. The analysis is useful in

Yuetao Liu; Yanjie Liu; Lining Sun; Ji Li

2009-01-01

11

Robust 300 C wire insulation system  

NASA Technical Reports Server (NTRS)

The objective of this program is to identify, develop, and demonstrate an optimum wire insulation system that is capable of continuous operation at 300 C. The system is to possess a combination of superior electrical (AC or DC), mechanical, and physical properties over the KAPTON (trademark) derived insulations described in MIL-W-81381 and those hybrid constructions identified in Air Force contract F33615-89-C-5606, commonly known as TKT constructions.

Nairus, John G.

1994-01-01

12

Establishment of a Switched-Reluctance Generator-Based Common DC Microgrid System  

Microsoft Academic Search

This paper presents a dc microgrid including a switched-reluctance generator (SRG) with isolated boost dc-dc converter, a battery energy storage system, and a single-phase three-wire (1P3W) load inverter for generating ac 220\\/110 V 60-Hz outputs. The 400-V dc grid is established by the SRG with dc 48-V output followed by a current-fed push-pull (CFPP) dc-dc converter. The robust commutation and

Yuan-Chih Chang; Chang-Ming Liaw

2011-01-01

13

DSP Sliding-Mode Controllers for Three-Phase Four-Wire Converters with Split DC Link Capacitor  

Microsoft Academic Search

This paper presents the voltage regulation system design for a three-phase four-wire voltage converter using sliding-mode control techniques. Two regulation systems proposed are applied to a three-leg voltage source converter with split dc link capacitor connected to the ac mains. System modelling and controllers syntheses with digital implementation are realized. Experimental results highlight the voltage regulation characteristics in terms of

V. Soares; P. Verdelho

2005-01-01

14

MultiLevel DC\\/DC Power Conversion System with Multiple DC Sources  

Microsoft Academic Search

A multilevel dc\\/dc power conversion system with multiple dc sources is proposed in this paper. With this conversion system, the output voltage can be changed almost continuously without any magnetic components. With this magnetic-less system, very high temperature operation is possible. Power loss and efficiency analysis is provided in the paper. Comparison results show that the system does not require

Miaosen Shen; Siemens VDO Automotive; Fang Z. Peng; Leon M. Tolbert

2009-01-01

15

GRYFFIN TALOS taut wire perimeter detection system  

Microsoft Academic Search

Perimeter security utilising a taut wire fence sensor system has been available for the last 30 years. There are a number of features which make such systems attractive for security applications. These include resistance to environmental affects, low nuisance alarm rate and high probability of detection. A taut wire fence constructed of barbed wire also acts as a deterrent, adding

G. Hellard

1998-01-01

16

Ultracapacitors + DC-DC converters in regenerative braking system  

Microsoft Academic Search

An ultracapacitor system for an electric vehicle has been implemented. The device allows higher accelerations and decelerations of the vehicle with minimal loss of energy and minimal degradation of the main battery pack. The system uses a DC-DC power converter, which is connected between the ultracapacitor and the main battery pack. The design has been optimized in weight and size,

J. W. Dixon; M. E. Ortuzar

2002-01-01

17

Integrated taut wire sensor alarm monitoring system  

Microsoft Academic Search

For many years mechanical taut wire intrusion detection systems have played a key role in protecting high risk facilities. The taut wire sensor has the advantage that it combines a physical barrier with an intrusion sensor, a useful feature where no fence is installed or planned. However, mechanical taut wire sensors have proven to have several major disadvantages, including: no

J. B. Morgan; M. R. Tennefoss

1986-01-01

18

Development of prototype DC superconducting cable for railway system  

NASA Astrophysics Data System (ADS)

High Temperature Superconducting (HTSC) wire has significant potential for railway system applications. HTSC wire is currently a promising candidate for various engineering applications such as transformers and motors for railway system. HTSC direct current (DC) cable is ideal for a feeder of the overhead contact line system between the substation and the electric train. We completed a prototype Bi-2223 tape based direct current cable for trial purposes of several meters length. In the energizing experiment the current of 1720 A successfully constantly flew.

Tomita, Masaru; Fukumoto, Yusuke; Suzuki, Kenji; Miryala, Muralidhar

2010-12-01

19

Welding of thin sheet of Al alloy (6082) by using Vario wire DC P-GMAW  

Microsoft Academic Search

This paper describes an investigation on the micro-structure, weld bead geometry, dilution rate and mechanical properties\\u000a of the butt and overlap weld joints of 1-mm-thick 6082 aluminium alloy sheet. Weld joints were produced with the help of a\\u000a variant of gas metal arc welding (GMAW) process, i.e. direct current-pulsed GMAW (DC P-GMAW), using a Vario wire. The capability\\u000a of the

Rakesh Kumar; Ulrich Dilthey; D. K. Dwivedi; S. P. Sharma; P. K. Ghosh

2009-01-01

20

An Assessment of High-Voltage DC Electrical Power in Aircraft Electrical Systems.  

National Technical Information Service (NTIS)

If the presently installed three-phase ac transmission system on aircraft were replaced by a higher voltage dc (HVDC) transmission using a ground return (the aircraft frame), a reduction in weight of wiring, number of wires, and total power losses equal t...

B. J. Wilson J. P. O'Connor

1970-01-01

21

Wire-rope emplacement of diagnostics systems  

SciTech Connect

The study reported here was initiated to determine if, with the Cable Downhole System (CDS) currently under development, there is an advantage to using continuous wire rope to lower the emplacement package to the bottom of the hole. A baseline design using two wire ropes as well as several alternatives are discussed in this report. It was concluded that the advantages of the wire-rope emplacement system do not justify the cost of converting to such a system, especially for LLNL's maximum emplacement package weights.

Burden, W.L.

1982-05-07

22

Quasi-Resonant DC Link Control of 3Dimensional Hysteresis Current PWM Technique in 3Phase 4Wired Power Quality Compensator  

Microsoft Academic Search

In this paper, quasi-resonant DC link (QRDCL) softswitching 3-dimensional hysteresis current control for power quality compensator is investigated. Power quality compensator here is the shunt active power filter in the 3-phase 4-wire system to compensate the imbalance, reactive power, harmonics and neutral current. The 3-dimensional hysteresis current PWM technique changes the system frame from a-b-c coordinate to alpha-beta-O coordinate for

Ming-hui Zhan; Man-chung Wong; Ying-duo Han

2005-01-01

23

Light rail systems without wires?  

Microsoft Academic Search

For over 110 years, the use of overhead wires to power streetcars and more recently their successors, light rail vehicles, has been considered unsightly and undesirable by politicians and the general public alike. At the turn of the century many cities passed ordinances against them and many alternative power feed concepts were attempted, the most successful being the slot or

J. D. Swanson

2003-01-01

24

Specifying DC chopper systems for electrochemical applications  

Microsoft Academic Search

This paper deals with information that customers, suppliers, and consultants should consider when specifying a high-current DC chopper system. It deals with specification of the major components, such as rectifier transformers, rectifiers, unregulated DC distribution bus, disconnect switches, choppers and cooling systems

Pamela S. Maniscalco; Vince Scaini; William E. Veerkamp

2001-01-01

25

Modeling of DC spacecraft power systems  

NASA Technical Reports Server (NTRS)

Future spacecraft power systems must be capable of supplying power to various loads. This delivery of power may necessitate the use of high-voltage, high-power dc distribution systems to transmit power from the source to the loads. Using state-of-the-art power conditioning electronics such as dc-dc converters, complex series and parallel configurations may be required at the interface between the source and the distribution system and between the loads and the distribution system. This research will use state-variables to model and simulate a dc spacecraft power system. Each component of the dc power system will be treated as a multiport network, and a state model will be written with the port voltages as the inputs. The state model of a component will be solved independently from the other components using its state transition matrix. A state-space averaging method is developed first in general for any dc-dc switching converter, and then demonstrated in detail for the particular case of the boost power stage. General equations for both steady-state (dc) and dynamic effects (ac) are obtained, from which important transfer functions are derived and applied to a special case of the boost power stage.

Berry, F. C.

1995-01-01

26

LANSCE Wire Scanner System Prototype: Switchyard Test  

SciTech Connect

On November 19, 2011, the beam diagnostics team of Los Alamos National Laboratory's LANSCE accelerator facility conducted a test of a prototype wire scanner system for future deployment within the accelerator's switchyard area. The primary focus of this test was to demonstrate the wire scanner control system's ability to extend its functionality beyond acquiring lower energy linac beam profile measurements to acquiring data in the switchyard. This study summarizes the features and performance characteristics of the electronic and mechanical implementation of this system with details focusing on the test results.

Sedillo, James D [Los Alamos National Laboratory

2012-04-11

27

Bidirectional AC-DC\\/DC-AC converter for power sharing of hybrid AC\\/DC systems  

Microsoft Academic Search

In this paper, some of the aspects related to the connectivity of DC microgrids to the main grid are investigated. A prototype system has been designed and implemented to address these aspects. The described system is dependent mainly on sustainable energy sources. Hence, a special care has been given to dealing with this kind of sources while designing different components

A. Mohamed; M. Elshaer; O. Mohammed

2011-01-01

28

Neutral Current of an Edison Wire System  

NSDL National Science Digital Library

This is an object learning lesson, created by Terry Bartelt of the Wisconsin Online Resource Center, on neutral current of an Edison wire system. The employment of Flash allows users to interact with the presentation. Overall, this is a nice introduction to this specific topic.

Bartelt, Terry L.

2010-09-23

29

A review of wiring system safety in space power systems  

NASA Technical Reports Server (NTRS)

Wiring system failures have resulted from arc propagation in the wiring harnesses of current aerospace vehicles. These failures occur when the insulation becomes conductive upon the initiation of an arc. In some cases, the conductive path of the carbon arc track displays a high enough resistance such that the current is limited, and therefore may be difficult to detect using conventional circuit protection. Often, such wiring failures are not simply the result of insulation failure, but are due to a combination of wiring system factors. Inadequate circuit protection, unforgiving system designs, and careless maintenance procedures can contribute to a wiring system failure. This paper approaches the problem with respect to the overall wiring system, in order to determine what steps can be taken to improve the reliability, maintainability, and safety of space power systems. Power system technologies, system designs, and maintenance procedures which have led to past wiring system failures will be discussed. New technologies, design processes, and management techniques which may lead to improved wiring system safety will be introduced.

Stavnes, Mark W.; Hammoud, Ahmad N.

1993-01-01

30

Towards a Fully Modular Power System Architecture for DC-DC Converters.  

National Technical Information Service (NTIS)

Fully modular power system architecture for dc-dc conversion, where low-power, low-voltage (input and output) building block dc- dc converters can be connected in any combination of series/parallel configurations at the output and/or at the input sides, h...

R. Ayyanar E. Ledezma

2006-01-01

31

Standalone Self-Excited Induction Generator with a Three-Phase Four-Wire Active Filter and Energy Storage System  

Microsoft Academic Search

This paper proposes a system, based on a self- excited induction generator with a shunt electronic converter, to feed isolated three-phase and single-phase linear or nonlinear loads. The electronic converter is composed by a three-phase four-wire voltage source inverter (VSI) and, connected to its dc side, two dc\\/dc converters. The VSI compensates the current harmonics, the reactive power and the

José Antonio Barrado; Robert Griñó; Hugo Valderrama

2007-01-01

32

Anti-slipping system improves wire saw performance  

NASA Technical Reports Server (NTRS)

System prevents wire saw slippage by providing sufficient friction to turn idler spools even when turns of wire on spools do not provide sufficient friction. Low cost system is easily applied to existing equipment.

Gallo, E. A.

1971-01-01

33

Low cost wire detection system  

Microsoft Academic Search

Power lines have always been of primary concern to helicopter pilots. In the past laser based systems have been built to alert the pilot to power lines in the flight path. These systems were heavy, required high power, suffered from high false alarm rates and were not considered cost effective even for military helicopters. Using a simple CW diode laser

P. Avizonis; B. Barron

1999-01-01

34

Energy measurement device wiring detection and examination training system design  

Microsoft Academic Search

To heighten the electrical measurement device wrong wiring detection speed and improve inspectors' working efficiency, analyzing the request of electrical measurement device wiring testing and examination training system, there put forward a whole design scheme and data collection device framework, PC Analysis system framework, and also gives a main algorithm of wrong wiring. The system has run in a ShanXi

Xingzhong Zhang; Gaoyun Liu

2009-01-01

35

Design approach for a laser wire and wire-like object detection system  

Microsoft Academic Search

A conceptual design and tradeoff study has been performed for a Wire and Wire-Like Object Detection System (WWLODS). The objective of the study was to recommend three alternative design approaches for a pod-mounted system to be carried on Army helicopters, to be capable of detecting 1\\/8 inch Army field wire, and to meet a weight goal of 50 pounds, a

B. B. Silverman; H. Heynau; R. J. Mongeon

1981-01-01

36

Dc-ac three-phase four-wire Z-source converter with hybrid PWM strategy  

Microsoft Academic Search

This paper presents a hybrid PWM strategy for dc-ac three-phase four-wire Z-source converters. The technique combines the theory of space-vector PWM with the ease of implementation of a triangular-comparison PWM. Such strategy reduces the effort of algorithm calculation. The introduction of the distribution ratio in this technique, allows the development of a systematic approach for implementation of either conventional or

E. C. dos Santos; J. H. G. Muniz; E. P. X. P. Filho; E. R. C. da Silva

2010-01-01

37

The forefront of practical superconducting wires  

Microsoft Academic Search

On the practical superconducting wires, such as Nb–Ti alloy wires, Nb3Sn compound wires, and bismuth system superconducting wires, the workability of long wire, transport critical current density, AC losses and mechanical properties were investigated. Practical superconducting wires of Nb–Ti alloy and Nb3Sn compound have already been used as DC superconducting windings, and are expected to be used for AC applications.

Yasuzo Tanaka

2000-01-01

38

ERCP wire systems: The long and the short of it  

PubMed Central

Guidewires are routinely used at the time of endoscopic retrograde cholangiopancreatography (ERCP) to gain and maintain access to the desired duct and aid in the advancement of various devices. Limitations of the traditional long-wire systems have led to the introduction of three proprietary short-wire systems. These systems differ in many respects but share two main principles: They lock a shorter wire in position to allow advancement or removal of various devices without displacement of the wire and they all allow for physician control of the wire. In this comprehensive review, we describe the key features of the three currently available short-wire systems: RX, Fusion and V systems. We also focus on the potential benefits and drawbacks that accompany the short-wire concept as a whole and each specific system in particular. Although the available data are limited, it appears that the use of the short-wire systems lead to reduced procedure, fluoroscopy and device exchange times, decreased sedation requirements, improved wire stability and increased endoscopist control of the wire. Furthermore, the physician-controlled wire-guided cannulation has the potential to decrease ampullary trauma and the rate of post-ERCP pancreatitis. The short guidewire systems appear to be an improvement over the traditional long-wire systems but further studies directly comparing the two approaches are needed.

Reddy, Shilpa Chandrupatla; Draganov, Peter V

2009-01-01

39

Efficient and ripple-mitigating dc–dc converter for residential fuel cell system  

Microsoft Academic Search

Proton exchange membrane fuel cell (PEMFC) systems for residential application require efficient and ripple-mitigating power conditioning system (PCS). The key point to reach it, is the design and control of the dc–dc converter. Based on the theoretical and experimental analysis of the traditional converter, this paper proposes a novel parallel-series full bridge (P-SFB) dc–dc converter, and improves its phase shifting

Yong Wang; Seeyoung Choi; Eunchul Lee

2009-01-01

40

Probabilistic security analysis of shipboard DC zonal electrical distribution systems  

Microsoft Academic Search

Due to significant gains in terms of survivability, weight, manning, and cost obtained from DC zonal electrical distribution systems (DC ZEDS), various practical applications of DC ZEDS to shipboard electric power systems are expected in the foreseeing future. How to ensure whether shipboard DC ZEDS under different power outage events is secure becomes important for real-time operation and planning of

Chun-Lien Su; Chun-Teng Yeh

2008-01-01

41

Overvoltage protection concept for DC railway systems  

Microsoft Academic Search

Protection concepts for DC railway systems are introduced, considering the different insulation of the rails and the earthing concepts. The requirements and ratings for gapless MO-surge arresters (or short: arresters) are based on the relevant EN standards and national guidelines. A newly developed hybrid voltage limiter, which combines overvoltage protection and the protection against dangerous touch voltages, is introduced.

Bernhard Richter

2007-01-01

42

The biomechanics of wire fixation in the Ilizarov system  

Microsoft Academic Search

The purpose of this study was to establish the optimal fixation of tensioned wires to the frame construct in the Ilizarov system. The usual torque to which the fixation bolts were tightened in clinical practice was established by serial testing of orthopaedic surgeons’ work in our unit.The force required to produce wire slippage from the different types of wire fixation

M. M. Mullins; A. W. Davidson; David Goodier; M. Barry

2003-01-01

43

Rule-Based Expert System for Designing DC-DC Converters  

Microsoft Academic Search

\\u000a The design of DC-DC converters mainly relies on the experience of the designer who is usually aided by simulation programs\\u000a such as SPICE. Since it is very difficult to design highly efficient and reliable converters, even for the experienced designer,\\u000a we developed a design automation tool for isolated DC-DC converters based on a rule-based expert system. We define a set

Seok Min Yoon; Jong Tae Kim

2006-01-01

44

Domain wall drag due to dc current injection into ferromagnetic nano-wires  

Microsoft Academic Search

We here experimentally demonstrate the domain wall depinning triggered by injecting the current into the domain wall. The domain wall is pinned at the connection of a large pad and a narrow wire prior to the current injection experiment. The pinned domain wall is freed and pushed into the wire at the critical current, only when the current is injected

T. Kimura; Y. Otani; I. Yagi; K. Tsukagoshi; Y. Aoyagi

2004-01-01

45

Design considerations for high-voltage DC bus architecture and wire mechanization for hybrid and electric vehicle applications  

Microsoft Academic Search

In electric and hybrid electric vehicle applications high-voltage (HV) DC bus is shared by multiple power converter units and energy storage systems. Each of these components should meet a set of common HV bus design requirements besides their own functional requirements. Selection of an appropriate HV DC bus architecture is intertwined with control dynamics and filter component sizing, together with

Mohammad N. Anwar; Sean E. Gleason; Timothy M. Grewe

2010-01-01

46

Comparison of DC and pulsed critical current characterisation of NbTi superconducting wires  

Microsoft Academic Search

The use of pulsed magnetic fields and currents for transport critical current characterisation has many potential benefits, but introduces challenges in obtaining measurements consistent with conventional DC characterisation for some types of sample. This will be illustrated by comparative DC and pulsed critical current testing of two dissimilar NbTi conductors. The factors influencing pulsed measurements will be identified, the prospects

Simon C. HOPKINS; Tadeusz JANOWSKI

2009-01-01

47

Real-time software for the wire per wire X-ray data acquisition system  

Microsoft Academic Search

This paper presents the software developments associated with the design and construction of a fast wire per wire detector system that will be used for high-speed data collection of linear time-resolved X-ray diffraction spectra. As the overall hardware architecture of the system relies on the extensive use of a standard RISC based plug-in module, the code implementation of some critical

F. Briquet-Laugier; P. Baumlin; C. Boulin; F. Golding; M. Koch; A. Epstein

2000-01-01

48

Real-time software for the wire per wire X-ray data acquisition system  

Microsoft Academic Search

This paper presents the software developments associated with the design and construction of a fast wire per wire detector system that will be used for high-speed data collection of linear time-resolved X-ray diffraction spectra. As the overall hardware architecture of the system relies on the extensive use of a standard RISC based plug-in module, the code implementation of some critical

F. Briquet-Laugier; P. Baumlin; C. Boulin; F. Golding; M. Koch; A. Epstein

1999-01-01

49

Sliding mode control for stabilizing DC-link of DC-DC converter in photovoltaic systems  

Microsoft Academic Search

As the maximum power point of a photovoltaic (PV) cell varies mainly with incident illumination and ambient temperature, the PV cell may generate a wide range of voltages and currents at the terminals. As a consequence, the PV cell itself cannot maintain a constant DC voltage and function as a DC voltage power supply source. To overcome this problem, a

W. Thammasiriroj; T. Nuchkrua; S. Ruayariyasub

2010-01-01

50

DSTATCOM for power quality improvement in a four-wire electric distribution system  

Microsoft Academic Search

This paper deals with the simulation of a Distribution Static Compensator (DSTATCOM) for power quality improvement in a four-wire electric distribution system. A three-phase Insulated Gate Bipolar Transistor (IGBT)-based Current-Controlled Voltage Source Inverter (CC-VSI) with a DC bus capacitor is used as a DSTATCOM. The DSTATCOM improves the supply power factor, eliminates harmonics, provides load balancing and improves the load

Bhim Singh; Alka Adya; A. P. Mittal; J. R. P. Gupta

2006-01-01

51

49 CFR 393.28 - Wiring systems.  

Code of Federal Regulations, 2013 CFR

...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS PARTS...Truck-Tractor, Trailer, and Motor Coach Wiring, October 1981,...

2013-10-01

52

49 CFR 393.28 - Wiring systems.  

Code of Federal Regulations, 2010 CFR

...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS PARTS...Truck-Tractor, Trailer, and Motor Coach Wiring, October 1981,...

2009-10-01

53

49 CFR 393.28 - Wiring systems.  

Code of Federal Regulations, 2010 CFR

...Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS PARTS...Truck-Tractor, Trailer, and Motor Coach Wiring, October 1981,...

2010-10-01

54

Multiterminal DC transmission system based on modular multilevel converter  

Microsoft Academic Search

A multi-terminal DC (MTDC) transmission system based on an innovative modular multilevel converter (MMC) is presented as a feasible approach to address the concerns regarding reliability and fault ride through capability of multi-terminal dc systems. Furthermore, MTDC using MMC may reduce construction costs and power losses in the converter stations. To demonstrate control flexibility, improved reliability and DC fault ride

Grain P Adam; Olimpo Anaya-Lara; Graeme Burt

2009-01-01

55

Interchip link system using an optical wiring method.  

PubMed

A chip-scale optical link system is presented with a transmitter/receiver and optical wire link. The interchip link system consists of a metal optical bench, a printed circuit board module, a driver/receiver integrated circuit, a vertical cavity surface-emitting laser/photodiode array, and an optical wire link composed of plastic optical fibers (POFs). We have developed a downsized POF and an optical wiring method that allows on-site installation with a simple annealing as optical wiring technologies for achieving high-density optical interchip interconnection within such devices. Successful data transfer measurements are presented. PMID:18709120

Cho, In-Kui; Ryu, Jin-Hwa; Jeong, Myung-Yung

2008-08-15

56

New Solar Cell Power Supply System Using a Boost Type Bidirectinal DC-DC Converter  

Microsoft Academic Search

A new solar cell power supply system is presented, in which the boost type bidirectional dc-dc converter and the simple control circuit with a small monitor solar cell are employed to track the maximum power point of the solar array. It is confirmed by the experiment that the new system has sufficiently precise tracking operation performance and satisfactorily high power

Hirofumi Matsuo; Fujio Kurokawa

1984-01-01

57

Automatic Physical Design of Large Wire-Wrap Digital Systems.  

National Technical Information Service (NTIS)

A system is described which automatically performs the detailed physical design of a wire-wrap digital system, given a completed logical design, chip placement, and user-specification of the particular component technology and wire-wrap package to be used...

L. C. Widdoes

1980-01-01

58

Vibration Simulation of Transducer System in Thermosonic Wire bonding  

Microsoft Academic Search

The vibration simulation model of transducer system in wire bonding was established by mechanical finite element method and verified by electric sine sweeping exciting method. The results show that, transducer system of wire bonder works with its second combination vibration mode that includes three nodes axial vibration of concentrator and one node radial vibration of capillary. There are many other

Long Zhili; Han Lei; Zhou Hongquan; Wu Yunxin; Zhong Jue

2005-01-01

59

Power systems analysis for direct current (dc) distribution systems  

SciTech Connect

Many standards, guidelines, etc., currently exist which provide guidance for dc power systems analysis. These documents are scattered throughout the industry (i.e., IEEE, UL, NEMA, GE, etc.), and primarily treat the subject as though hand calculations are being performed. It is the intent of this paper to provide guidance for performing computer aided dc power systems analyzes. This paper will cover load flow/voltage drop and short circuit calculations.

Fleischer, K. [Public Service Electric and Gas, Hancock`s Bridge, NJ (United States). Salem Nuclear Generating Station] [Public Service Electric and Gas, Hancock`s Bridge, NJ (United States). Salem Nuclear Generating Station; Munnings, R.S. [VECTRA Technologies, Inc., Lincolnshire, IL (United States)] [VECTRA Technologies, Inc., Lincolnshire, IL (United States)

1996-09-01

60

High-Frequency Transformer Isolated Soft-Switching DC-DC Converter for Fuel Cell Cogeneration System  

Microsoft Academic Search

A high-frequency transformer isolated soft-switching DC-DC converter for fuel-cell cogeneration systems with utility-interactive inverter is investigated. The new type DC-DC converter offers a high efficiency in a wide power range, from rated to low power, by means of a new soft-switching topology. A prototype of the DC-DC converter and utility-interactive inverter cascade system is practically evaluated to confirm the fine

S. Sumiyoshi; H. Omori; Y. Nakamura; N. Tan; Y. Nishida

2006-01-01

61

A study of cooling magnet-wire of the brushless DC motor for car air conditioner  

Microsoft Academic Search

The electric compressor for car air-conditioners is very high ambient temperature compared with the compressor for household appliances. For this reason, the motor built in this compressor has severe temperature conditions. A cooling design is important in order to improve motor operating temperature on In this research, this temperature is measured paying attention to a magnet wire. Moreover, the cooling

Tomokazu Naruta; Yuji Akiyama; Yuta Niwa

2008-01-01

62

System energy minimization via joint optimization of the DC-DC converter and the core  

Microsoft Academic Search

This paper addresses the problem of designing energy- efficient embedded systems by jointly optimizing the power consumption of both the DC-DC converter and the computational core. Past work has shown that there exists a minimum energy operating point (MEOP) in the subthreshold region for computational cores (C-MEOP), at which the dynamic and leakage powers are balanced. The MEOP is defined

Rami A. Abdallah; Pradeep S. Shenoy; Naresh R. Shanbhag; Philip T. Krein

2011-01-01

63

Smart optimal control of DC-DC boost converter in PV systems  

Microsoft Academic Search

Proportional integral derivative (PID) controllers are usually used to control DC-DC boost converters in PV systems. However, they have to be tuned based on certain defined operating range using averaged mathematical models. Loading conditions have great effect on PI controllers; PI controllers are subjected to failure under dramatic load changes. This limits the PI controller's operating range. Moreover, transient and

M. Elshaer; A. Mohamed; O. Mohammed

2010-01-01

64

Novel solar cell power supply system using the multiple-input DC-DC converter  

Microsoft Academic Search

Recently, clean electric power generation systems have attracted a great deal of social attention to exploit clean energy resources such as solar arrays, wind generators, fuel cells, etc. In this case, the multiple-input DC-DC power converter is useful to combine the several input power sources and to supply the regulated output voltage for the load. The novel solar cell power

Hirohmi Matsuo; Kimiyoshi Kobayashi; Yutaka Sekine; Matsuyoshi Asano; Lin Wenzhong

1998-01-01

65

The Application of Active Superconducting DC Fault Current Limiter in Hybrid AC\\/DC Power Supply Systems  

Microsoft Academic Search

This paper presents a new topology of the active superconducting DC fault current limiter (DC-SFCL) applied in the hybrid AC\\/DC power supply systems. The proposed DC-SFCL is composed of superconducting transformer, DC chopper and voltage source converter (VSC). The primary winding of the transformer is connected in series with DC transmission line, and the second winding is connected with AC

Jing Shi; Yuejin Tang; Lei Chen; Jin Wang; Li Ren; Jingdong Li; Liang Li; Tao Peng; Shijie Cheng

2008-01-01

66

Gryffin TALOS taut wire perimeter detection system real world experiences  

Microsoft Academic Search

The development of taut wire detectors over the last 30 years has continued to ensure acceptance of this technology in the perimeter security applications. There are a number of features which make such systems attractive for security, applications which include resistance to environmental affects, low nuisance alarm rate and high probability of detection. A taut wire fence constructed of barbed

G. Hellard

1999-01-01

67

Wireless monitoring system for granary based on 1-wire  

Microsoft Academic Search

On the basis of analyzing the importance of grain temperature and humidity measurement, this paper introduces a temperature and humidity wireless monitoring system for barn based on 1-wire. The wireless monitoring and control of the terminal node by the host computer is realized through a combination of wireless and wired mode. Because there are more measuring points in the barn,

Lun Cuifen; Ma Jiwei; Fan Hua; Liu Ce; Sun Lei; Yu Jingjing

2010-01-01

68

Plasmon hybridization in parallel nano-wire systems  

SciTech Connect

We apply the plasmon hybridization method to a double-nano-wire system, providing a simple and intuitive description of the plasmon excitations in the system. We apply the two-center cylindrical coordinate system for mathematical convenience and find an explicit form of the surface plasmon oscillations, in terms of the interaction between the bare plasmon modes of the individual surfaces of the nano-wires. We present numerical results to display how the plasmon excitations of the system depend on nano-wire separation when there is no angular momentum transfer, i.e., when m = 0.

Moradi, Afshin [Department of Nano Science, Kermanshah University of Technology, Kermanshah 67178-63766 (Iran, Islamic Republic of) and Department of Nano Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), Tehran 19395-5531 (Iran, Islamic Republic of)

2011-06-15

69

System reconfiguration on shipboard DC zonal electrical system  

Microsoft Academic Search

In this paper, an automated agent based reconfiguration scheme has been proposed for the DC zonal shipboard electrical system (SES). It is shown that the scheme can reconfigure the system following a disturbance in order to maintain the continuity of supply to loads. The paper identifies the main design issues, which include the number and location of the sectionalizers, primary

Mesut E Baran; Nikhil Mahajan

2005-01-01

70

Aircraft wire system laboratory development : phase I progress report.  

SciTech Connect

An aircraft wire systems laboratory has been developed to support technical maturation of diagnostic technologies being used in the aviation community for detection of faulty attributes of wiring systems. The design and development rationale of the laboratory is based in part on documented findings published by the aviation community. The main resource at the laboratory is a test bed enclosure that is populated with aged and newly assembled wire harnesses that have known defects. This report provides the test bed design and harness selection rationale, harness assembly and defect fabrication procedures, and descriptions of the laboratory for usage by the aviation community.

Dinallo, Michael Anthony; Lopez, Christopher D.

2003-08-01

71

Wire rope research and logging. [Skyline and dragline systems  

SciTech Connect

The various factors affecting the service life of wire ropes in skyline and dragline systems are discussed: design, geometry, sheave geometry, wear and lubrication, sheave hardness, pickup of small rocks, etc. (DLC)

Morgenstern, M.H.

1981-01-01

72

Novel Solar-Cell Power Supply System Using a Multiple-Input DC–DC Converter  

Microsoft Academic Search

Recently, the clean electric power generation systems have attracted a great deal of social attention to exploit the clean-energy resources such as solar arrays, wind generators, fuel cells, and so forth. In this case, a multiple-input dc–dc converter is useful to combine the several input power sources and to supply the regulated output voltage for the load from the power

Kimiyoshi Kobayashi; Hirofumi Matsuo; Yutaka Sekine

2006-01-01

73

DC isolation and protection system and circuit  

NASA Technical Reports Server (NTRS)

A precision analog electronic circuit that is capable of sending accurate signals to an external device that has hostile electric characteristics, including the presence of very large common mode voltages. The circuit is also capable of surviving applications of normal mode overvoltages of up to 120 VAC/VDC for unlimited periods of time without damage or degradation. First, the circuit isolates the DC signal output from the computer. Means are then provided for amplifying the isolated DC signal. Further means are provided for stabilizing and protecting the isolating and amplifying means, and the isolated and amplified DC signal which is output to the external device, against overvoltages and overcurrents.

Wagner, Charles A. (Inventor); Kellogg, Gary V. (Inventor)

1991-01-01

74

Cryogenic System for DC Superconducting Power Transmission Line  

Microsoft Academic Search

Due to the recent developments of the electric power devices and the HTS power cables, DC superconducting power transmission system is considered to be practical. As one of the R & D issues of the DC superconducting power transmission system, we measured the radiation heat of the thermally-isolated stainless steel pipes with different surfaces. As the result, one sheet of

Makoto Hamabe; Atsushi Sasaki; Tosin S. Famakinwa; Akira Ninomiya; Yasuhide Ishiguro; Satarou Yamaguchi

2007-01-01

75

BAE Systems Radiation Hardened SpaceWire ASIC and Roadmap  

NASA Technical Reports Server (NTRS)

An Application Specific Integrated Circuit (ASIC) that implements the SpaceWire protocol has been developed in a radiation hardened 0.25 micron CMOS, technology. This effort began in March 2003 as a joint development between the NASA Goddard Space Flight Center (GSFC) and BAE Systems. The BAE Systems SpaceWire ASlC is comprised entirely of reusable core elements, many of which are already flight-proven. It incorporates a 4-port SpaceWire router with two local ports, dual PC1 bus interfaces, a microcontroller, 32KB of internal memory, -and a memory controller for additional external memory use. The SpaceWire ASlC is planned for use on both the Geostationary Operational Environmental Satellites (GOES)-R and the Lunar Reconnaissance Orbiter (LRO). Engineering parts have already been delivered to both programs. This paper discusses the SpaceWire protocol and those elements of it that have been built into the current SpaceWire reusable core. There are features within the core that go beyond the current standard that can be enabled or disabled by the user and these will be described. The adaptation of SpaceWire to BAE Systems' On Chip Bus (OCB) for compatibility with the other reusable cores will be discussed. Optional configurations within user systems will be shown. The physical imp!ementation of the design will be described and test results from the hardware will be discussed. Finally, the BAE Systems roadmap for SpaceWire developments will be discussed, including some products already in design as well as longer term plans.

Berger, Richard; Milliser, Myrna; Kapcio, Paul; Stanley, Dan; Moser, David; Koehler, Jennifer; Rakow, Glenn; Schnurr, Richard

2006-01-01

76

WireGL: a scalable graphics system for clusters  

Microsoft Academic Search

We describe WireGL, a system for scalable interactive rendering on a cluster of workstations. WireGL provides the familiar OpenGL API to each node in a cluster, virtualizing multiple graphics accelerators into a sort-first parallel renderer with a parallel interface. We also describe techniques for reassembling an output image from a set of tiles distributed over a cluster. Using flexible display

Greg Humphreys; Matthew Eldridge; Ian Buck; Gordan Stoll; Matthew Everett; Pat Hanrahan

2001-01-01

77

A Laser-Wire System at the ATF Extraction Line  

SciTech Connect

A new laser-wire (LW) system has been installed at the ATF extraction line at KEK, Tsukuba. The system aims at a micron-scale laser spot size and employs a mode-locked laser system. The purpose-built interaction chamber, light delivery optics, and lens systems are described, and the first results are presented.

Boogert, S.T.; Blair, G.; Boorman, G.; Bosco, A.; Deacon, L.; Driouichi, C.; Karataev, P.; /Royal Holloway, U. of London; Kamps, T.; /BESSY, Berlin; Delerue, N.; Dixit, S.; Foster, B.; Gannaway, F.; Howell, D.F.; Qureshi, M.; Reichold, A.; Senanayake, R.; /Oxford U.; Aryshev, A.; Hayano, H.; Kubo, K.; Terunuma, N.; Urakawa, J.; /KEK, Tsukuba /Liverpool U. /Cockcroft Inst. Accel. Sci. Tech. /SLAC

2007-02-12

78

Effect of impurities on the steady component of the current in a quantum wire under the joint action of ac and dc fields  

SciTech Connect

The current flowing along a cylindrical quantum wire with a superlattice in the case of the simultaneous application of dc and ac fields is calculated. It is assumed that the wire contains impurity centers, whose ionization results in the generation of nonequilibrium carriers in the conduction band. It is found that the dependence of the steady component of the current on the ac-field frequency is a step-like function. It is shown that the distance between steps depends on the conduction miniband width and the transverse quantum confinement parameters and is independent of the impurity-level depth.

Zav'yalov, D. V., E-mail: sed@fizmat.vspu.ru; Kryuchkov, S. V. [Volgograd State Pedagogical University (Russian Federation)

2008-10-15

79

A carrier modulation method for minimizing the dc link capacitor current ripple of the HEV DC-DC converter and inverter systems  

Microsoft Academic Search

Minimization of the dc capacitor is an essential step towards developing and manufacturing compact low-cost hybrid electric vehicle (HEV) converter\\/inverter systems for high temperature operation, long life and high reliability. Previously, most papers have been focused on the AC-DC-AC pulse-width modulation (PWM) converters with relatively complicated close-loop control methods, while few papers have analyzed the DC-DC-AC PWM converters that also

Xi Lu; Wei Qian; Dong Cao; Fang Zheng Peng; Jianfeng Liu

2011-01-01

80

Operational environments for electrical power wiring on NASA space systems  

NASA Technical Reports Server (NTRS)

Electrical wiring systems are used extensively on NASA space systems for power management and distribution, control and command, and data transmission. The reliability of these systems when exposed to the harsh environments of space is very critical to mission success and crew safety. Failures have been reported both on the ground and in flight due to arc tracking in the wiring harnesses, made possible by insulation degradation. This report was written as part of a NASA Office of Safety and Mission Assurance (Code Q) program to identify and characterize wiring systems in terms of their potential use in aerospace vehicles. The goal of the program is to provide the information and guidance needed to develop and qualify reliable, safe, lightweight wiring systems, which are resistant to arc tracking and suitable for use in space power applications. This report identifies the environments in which NASA spacecraft will operate, and determines the specific NASA testing requirements. A summary of related test programs is also given in this report. This data will be valuable to spacecraft designers in determining the best wiring constructions for the various NASA applications.

Stavnes, Mark W.; Hammoud, Ahmad N.; Bercaw, Robert W.

1994-01-01

81

Wired.  

ERIC Educational Resources Information Center

Discusses technology's impact on scoreboard design: the development of the light-emitting diode (LED) display. How the LED system works is explained, as are the advantages and disadvantages of LED compared with incandescent lamp boards. Final comments address deciding on materials for scoreboard casings. (GR)

Conklin, Aaron R.

1998-01-01

82

Damping phenomena in a wire rope vibration isolation system  

NASA Technical Reports Server (NTRS)

A study is presented of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators, with emphasis placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase plane trajectories, and frequency response curves are obtained. A semiempirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed, and the results are compared to experimental data. Several observations and conclusions are made about the dynamic phenomena in a typical wire rope vibration isolation system based on the experimental and semiempirical results.

Tinker, M. L.; Cutchins, M. A.

1992-01-01

83

Damping phenomena in a wire rope vibration isolation system  

NASA Technical Reports Server (NTRS)

A study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators is presented. Emphasis is placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase trajectories, and frequency response curves were obtained. A semi-empirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed and results are compared to experimental data. Conclusions about dynamic phenomena in the wire rope system are made based on the experimental and semi-empirical results.

Tinker, Michael L.; Cutchins, Malcolm A.

1990-01-01

84

Damping phenomena in a wire rope vibration isolation system  

NASA Astrophysics Data System (ADS)

A study is presented of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators, with emphasis placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase plane trajectories, and frequency response curves are obtained. A semiempirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed, and the results are compared to experimental data. Several observations and conclusions are made about the dynamic phenomena in a typical wire rope vibration isolation system based on the experimental and semiempirical results.

Tinker, M. L.; Cutchins, M. A.

1992-08-01

85

Damping phenomena in a wire rope vibration isolation system  

NASA Astrophysics Data System (ADS)

A study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators is presented. Emphasis is placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase trajectories, and frequency response curves were obtained. A semi-empirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed and results are compared to experimental data. Conclusions about dynamic phenomena in the wire rope system are made based on the experimental and semi-empirical results.

Tinker, Michael L.; Cutchins, Malcolm A.

86

A Bi-Directional Isolated DC/DC Converter as a Core Circuit for 3.3-kV/6.6-kV Power Conversion Systems in the Next Generation  

NASA Astrophysics Data System (ADS)

This paper describes a bi-directional isolated dc/dc converter considered as a core circuit of 3.3-kV/6.6-kV high-power-density power conversion systems in the next generation. The dc/dc converter is intended to use power switching devices based on SiC and/or GaN, which will be available on the market in the near future. A 350-V, 10-kW and 20kHz dc/dc converter is designed, constructed and tested in this paper. It consists of two single-phase full-bridge converters with the latest trench-gate Si-IGBTs and a 20-kHz transformer with a nano-crystalline soft-magnetic material core and litz wires. The transformer plays an essential role in achieving galvanic isolation between the two full-bridge converters. The overall efficiency from the dc-input to dc-output terminals is accurately measured to be as high as 97%, excluding gate drive circuit and control circuit losses from the whole loss. Moreover, loss analysis is carried out to estimate effectiveness in using SiC-based power switching devices. The loss analysis clarifies that the use of SiC-based power devices may bring a significant reduction in conducting and switching losses to the dc/dc converter. As a result, the overall efficiency may reach 99% or higher.

Inoue, Shigenori; Akagi, Hirofumi

87

Damping phenomena in a wire rope vibration isolation system  

Microsoft Academic Search

A study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators is presented. Emphasis is placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase trajectories, and frequency response curves were obtained. A semi-empirical model having nonlinear stiffness, nth-power

Michael L. Tinker; Malcolm A. Cutchins

1990-01-01

88

Damping phenomena in a wire rope vibration isolation system  

Microsoft Academic Search

A study is presented of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators, with emphasis placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase plane trajectories, and frequency response curves are obtained. A semiempirical model having nonlinear stiffness,

M. L. Tinker; M. A. Cutchins

1992-01-01

89

Risk management in fly-by-wire systems  

NASA Technical Reports Server (NTRS)

A general description of various types of fly-by-wire systems is provided. The risks inherent in digital flight control systems, like those used in the Space Shuttle, are identified. The results of a literature survey examining risk management methods in use throughout the aerospace industry are presented. The applicability of these methods to the Space Shuttle program is discussed.

Knoll, Karyn T.

1993-01-01

90

Modified Wire Clamp System for Thirty-Liter Niskin Bottles.  

National Technical Information Service (NTIS)

A modified clamping system for 30-liter Niskin bottles, consisting of a wire stop, a socket block, and a toggle clamp, has been designed and has been tested at sea. The modified system makes deployment and recovery of the Niskin bottles considerably easie...

T. R. Hammar P. L. Sachs M. P. Bacon

1988-01-01

91

SNMP-based Integrated Wire\\/wireless Device Management System  

Microsoft Academic Search

Wireless devices become familiar. We regard digital utilities' development as a middle of way to ubiquitous computing environment. This change of network access environment at the end user brings more possibility to hack wireless devices. Lost of a device brings side-effects of private information problems. Thus, we propose an integrated wire\\/wireless device management system. The proposed system monitors devices, manages

Soo-Jin Jung; Jong-Hyouk Lee; Young-Ju Han; Jong-Hyun Kim; Jung-Chan Na; Tai-Myoung Chung

2007-01-01

92

Overshoot Damping Control of DC Current at Deblock in AC-DC Interconnected System with Externally Commutated Converters  

Microsoft Academic Search

Deblock of AC-DC interconnected system with externally commutated converters generally adopts soft start which makes trigger delay angle about 90 degrees and starts DC voltage from about 0kV. High DC voltage, however, is possibly caused by relation between the deblock signal and AC voltage phase at the commutation start of converter, resulting to overdue current. Consequently, overshoot of DC current

Keiji Kogiso; Takaaki Shimonosono

2008-01-01

93

Voltage and Frequency Controller for a Three-Phase Four-Wire Autonomous Wind Energy Conversion System  

Microsoft Academic Search

This paper deals with control of voltage and frequency of an autonomous wind energy conversion system (AWECS) based on capacitor-excited asynchronous generator and feeding three-phase four-wire loads. The proposed controller consists of three single-phase insulated gate bipolar junction transistor (IGBT)-based voltage source converters (VSCs) and a battery at dc link. These three single-phase VSCs are connected to each phase of

Bhim Singh; Gaurav Kumar Kasal

2008-01-01

94

Minimizing DC capacitor current ripple and DC capacitance requirement of the HEV converter\\/inverter systems  

Microsoft Academic Search

This paper presents an accurate theory of calculating the DC link capacitor voltage ripples (Ampere-Second) and current ripples (Irms) for inverters and PWM rectifiers, which are most commonly used in hybrid electric vehicle (HEV) converter\\/inverter systems. The results are analyzed and summarized into graphs according to the theory, which helps to find the right capacitance value for a given voltage

Xi Lu; Fang Zheng Peng

2009-01-01

95

New DC–DC Converter for Energy Storage System Interfacing in Fuel Cell Hybrid Electric Vehicles  

Microsoft Academic Search

The use of energy storage devices such as batteries or supercapacitors is almost mandatory in fuel cell hybrid electric vehicles, in order to guarantee load leveling, assuring braking energy recovery and good performances in transient operations. To this end, converters with bidirectional power flows are needed to connect the accumulators to the dc-link of the motor drive system. In this

Mario Marchesoni; Camillo Vacca

2007-01-01

96

THREE-PHASE COMPENSATOR FOR LOAD BALANCING AND REACTIVE POWER COMPENSATION IN THREE-PHASE, FOUR-WIRE ELECTRIC POWER DISTRIBUTION SYSTEMS  

Microsoft Academic Search

This paper deals with a three-phase active power compensator (APC) to compensate reactive power and to balance unbalanced loads in the three-phase four-wire electric power distribution system. An APC is realized employing three single phase IGBT based VSI bridges with a common dc bus capacitor. Reference supply currents are estimated using P-I control over the average dc bus voltage and

BHIM SINGH; K. AL-HADDAD; A. CHANDRA; D. P. KOTHARI

1998-01-01

97

Technique for DC Restoration in AC Coupled Display Systems.  

National Technical Information Service (NTIS)

Described is a technique for DC restoration in AC coupled display systems which includes histogramming, more specifically calculation of histogram values, of the difference in gray levels between two adjacent picture lines on a picture element by picture ...

G. R. Jones P. K. Raimondi

1980-01-01

98

Modeling PWM DC-DC converter as discrete input\\/continuous output system and its application to system local controllability  

Microsoft Academic Search

Periodic nature is always overlooked whenever power stage of a PWM DC-DC converter is modeled as averaged or sampled-data system. So these models are not suitable for studying a generalized system in cascade to the converter-power-stage. As a result, the former studies of the system local controllability or observability were always application oriented. In this paper, the authors have modeled

Muhammad Mansoor Khan; Wu Zhi-Ming

2001-01-01

99

Development of a DC propulsion system for an electric vehicle  

Microsoft Academic Search

The suitability of the Eaton automatically shifted mechanical transaxle concept for use in a near-term dc powered electric vehicle is evaluated. A prototype dc propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the contractor's site. The system consisted of a two-axis, three-speed, automatically-shifted mechanical transaxle, 15.2

W. L. Kelledes

1984-01-01

100

Reliability analysis of a direct parallel connected n+1 redundant power system based on highly reliable DC\\/DC modules  

Microsoft Academic Search

An n+1 redundant system using modular hybrid DC\\/DC converters connected in parallel where the normally associated isolation diodes are omitted is described. Reliability and efficiency analysis of the systems was performed, based on a comparison between the system described and a system based on a conventional (uninterruptible power system) UPS with added redundant functions. It is concluded that the proposed

L. Thorsell; P. Lindman

1988-01-01

101

30 CFR 77.704-11 - Use of grounded messenger wires; ungrounded systems.  

Code of Federal Regulations, 2013 CFR

...messenger wires; ungrounded systems. Solely for purposes of grounding ungrounded high-voltage power systems, grounded messenger wires used to suspend the cables of such systems may be used as a grounding...

2013-07-01

102

30 CFR 75.705-11 - Use of grounded messenger wires; ungrounded systems.  

Code of Federal Regulations, 2013 CFR

...messenger wires; ungrounded systems. Solely for purposes of grounding ungrounded high-voltage power systems, grounded messenger wires used to suspend the cables of such systems may be used as a grounding...

2013-07-01

103

Design and implementation of dc-bus system module for parallel integrated sustainable energy conversion systems  

Microsoft Academic Search

In this paper, a performance analysis of a highly integrated, high-performance dc-bus system module is presented. This module introduces a solution for medium & low voltage DC distribution applications. It is designed for applications requiring a single bus solution to control up to twelve DC-sources sharing same dc-bus and having same dc-voltage level. The bus is also designed to interface

Mahmoud M. Amin; O. A. Mohammed

2011-01-01

104

Further experiences with aluminium wire seals for bakeable vacuum systems  

Microsoft Academic Search

The use of aluminium cemented seals in vacuum systems has been further investigated to find the effect of the flange surface finish on the adhesion of the aluminium joint and the performance of such seals in bakeable apparatus. Aluminium wire clamped between stainless-steel flanges and baked at 300° C formed more adherent joints as the surface finish was decreased from

L. Elsworth; L. Holland; L. Laurenson

1960-01-01

105

Electrically Powered Wire Localization System for Mobile Robots  

Microsoft Academic Search

Among the technologies for mobile robot navigation, electrically powered wire-based navigation has the advantages of resisting environmental condition variance and readily sensing. In corresponding sensing systems, anisotropic magnetoresistive (AMR) sensors are desirable due to their excellent performances such as extreme sensitivity, wide linear range, low noise, and highly reliability. This paper proposes several positioning algo- rithms based on such sensing

Jingyu Lin; Ziguang Lu; Yonghua Zhou

2011-01-01

106

NASA/BAE SYSTEMS SpaceWire Effort  

NASA Technical Reports Server (NTRS)

This paper discusses the state of the NASA and BAE SYSTEMS developments of SpaceWire. NASA has developed intellectual property that implements SpaceWire in Register Transfer Level (RTL) VHDL for a SpaceWire link and router. This design has been extensively verified using directed tests from the SpaceWire Standard and design specification, as well as being randomly tested to flush out hard to find bugs in the code. The high level features of the design will be discussed, including the support for multiple time code masters, which will be useful for the James Webb Space Telescope electrical architecture. This design is now ready to be targeted to FPGA's and ASICs. Target utilization and performance information will be presented for Spaceflight worthy FPGA's and a discussion of the ASIC implementations will be addressed. In particular, the BAE SYSTEMS ASIC will be highlighted which will be implemented on their .25micron rad-hard line. The chip will implement a 4-port router with the ability to tie chips together to make larger routers without external glue logic. This part will have integrated LVDS drivers/receivers, include a PLL and include skew control logic. It will be targeted to run at greater than 300 MHz and include the implementation for the proposed SpaceWire transport layer. The need to provide a reliable transport mechanism for SpaceWire has been identified by both NASA And ESA, who are attempting to define a transport layer standard that utilizes a low overhead, low latency connection oriented approach that works end-to-end. This layer needs to be implemented in hardware to prevent bottlenecks.

Rakow, Glenn Parker; Schnurr, Richard G.; Kapcio, Paul

2003-01-01

107

Dc power supplies and hard-tube power conditioning systems  

SciTech Connect

In this lecture, we shall discuss some of the major characteristics of dc power supplies and hard-tube pulsers, along with many of their PCS limiting properties and several of the more powerful vacuum tubes that are currently available for larger hard-tube pulsers systems. The initial topic will be elementary dc power supplies, operating with standard 60 Hz AC input power. The full-wave bridge design will be discussed in detail, illustrating the majority of the significant circuit parameters.

Sarjeant, W.J.

1980-01-01

108

AC versus DC distribution systems- Did we get it right?  

SciTech Connect

We presently enjoy a predominantly ac electrical distribution system, the engineering basis for which was designed over 100 years ago. While ac distribution systems have served us well, we should periodically pause to assess what opportunities we have accepted or been denied by the overwhelming predominance of ac electrical power distribution systems. What opportunities could be obtained by engineering dc distribution into at least portions of our present system? What advantages of the present ac distribution system should be recognized and protected? This paper will focus on distribution within premise and low-voltage distribution systems. Specifically, we will address the conversion efficiency costs of adopting various premise ac and dc distribution system topologies. According to a simple predictive model formulated in this paper, premise residential dc distribution will incur unfavorable total conversion efficiency compared with existing ac premise distribution. However, if a residence is supplied by a fuel cell or another dc generator, the total conversion efficiency within a residential dc distribution system could be similar to, or even better than, that for ac distribution.

Hammerstrom, Donald J.

2007-06-28

109

Model-Based Testability Assessment and Directed Troubleshooting of Shuttle Wiring Systems  

NASA Technical Reports Server (NTRS)

We have recently completed a pilot study on the Space shuttle wiring system commissioned by the Wiring Integrity Research (WIRe) team at NASA Ames Research Center, As the space shuttle ages, it is experiencing wiring degradation problems including arcing, chaffing insulation breakdown and broken conductors. A systematic and comprehensive test process is required to thoroughly test and quality assure (QA) the wiring systems. The NASA WIRe team recognized the value of a formal model based analysis for risk-assessment and fault coverage analysis. However. wiring systems are complex and involve over 50,000 wire segments. Therefore, NASA commissioned this pilot study with Qualtech Systems. Inc. (QSI) to explore means of automatically extracting high fidelity multi-signal models from wiring information database for use with QSI's Testability Engineering and Maintenance System (TEAMS) tool.

Deb, Somnath; Domagala, Chuck; Shrestha, Roshan; Malepati, Venkatesh; Cavanaugh, Kevin; Patterson-Hine, Ann; Sanderfer, Dwight; Cockrell, Jim; Norvig, Peter (Technical Monitor)

2000-01-01

110

Channel Characterization and EMC Assessment of a PLC System for Spacecraft DC Differential Power Buses  

Microsoft Academic Search

This paper investigates the possibility of using the powerline communications (PLC) technology to transmit data along differential dc power buses employed in spacecraft. To this end, a point-to-point interconnection between the power control and distribution unit (PCDU) and a dc\\/dc converter is consid- ered. The power bus is composed of a twisted-wire pair (TWP) above ground, and capacitive coupling and

Flavia Grassi; Sergio A. Pignari; Johannes Wolf

2011-01-01

111

A purely ultracapacitor energy storage system hybrid electric vehicles utilizing a based DC-DC boost converter  

Microsoft Academic Search

The design and testing of a purely ultracapacitor energy storage system for the improvement of hybrid electric vehicles is presented. The system utilizes two large ultracapacitor banks for energy storage and a dc-dc boost converter that is capable of supplying 8 kW for voltage regulation. The system provides greater roundtrip efficiency over batteries, improves a vehicle's ability to recapture energy

Erik J. Cegnar; Herb L. Hess; Brian K. Johnson

2004-01-01

112

Magnetoimpedance effect of the Ni80Fe20/Cu composite wires: The influence of DC current imposed on the Cu base  

NASA Astrophysics Data System (ADS)

In this paper, the copper composite wires of 75 ?m in diameter with a sputtered layer of Ni80Fe20 permalloy were prepared, with a DC current applied to the basal Cu terminals during the fabrication process. The influence of the DC current on the magnetic configuration and Magneto-Impedance (MI) effect was studied. The results indicate that both the current amplitude and actuation duration have significant effect on the magnetic properties of the Ni80Fe20 layer. With appropriate current applied, the induced magnetic field leads to a circumferential magnetic domain structure and reduces significantly the equivalent anisotropy field of Ni80Fe20 layer. Then, the GMI ratio of the composite wires was significantly increased. A maximum GMI of 194.8% can be reached when the current was fixed at 100 mA and the Ni80Fe20 thickness is 780 nm. If the Ni80Fe20 thickness is above 780 nm, the coercivity of the coating layer increases while the GMI ratio of the composite wire reduces, since the magnetic anisotropy of the Ni80Fe20 layer varies from circumferential to longitudinal. The results were explained combining the thermal and magnetic effects of current.

Chen, Delu; Li, Xin; Ji, Xiaofeng; Zhao, Qiang; Ruan, Jianzhong; Zhao, Zhenjie

2014-06-01

113

A pseudodifferential amplifier for bioelectric events with DC-offset compensation using two-wired amplifying electrodes  

Microsoft Academic Search

Most wired active electrodes reported so far have a gain of one and require at least three wires. This leads to stiff cables, large connectors and additional noise for the amplifier. The theoretical advantages of amplifying the signal on the electrodes right from the source has often been described, however, rarely implemented. This is because a difference in the gain

Thomas Degen; Heinz Jäckel

2006-01-01

114

Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field  

NASA Astrophysics Data System (ADS)

Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

2013-07-01

115

A framework for SFC/DC system data analysis  

NASA Technical Reports Server (NTRS)

The Shop Floor Control/Data Collection (SFC/DC) system is one of four major modules of the Integrated Work Control System being implemented at the NASA Kennedy Space Center. The SFC/DC system, which has been in operation approximately one and a half years, collects detailed information regarding the duration of tasks as well as work stoppages duration. This information needs to be effectively analyzed, so as be able to manage the shuttle processing activities under the continuous improvement philosophy. We have studied the contents and form of the SFC/DC database, and based on the results of such study, we have designed a Shop floor Modeling, Analysis, and Reporting Tool (SMART). SMART is a collection of compatible tools (off-the-shelf as well as customized C-based tools) that work cohesively to prepare inputs for the analysis models and process the various models. The feasibility of SMART has been demonstrated through an initial prototype.

Centeno, Martha A.

1993-01-01

116

Firing angle modulation for elimination transformer dc currents in coupled ac-dc systems  

Microsoft Academic Search

A method of eliminating dc components of the currents in the transformer windings of a dc converter is presented. The method uses the technique of firing angle modulation. It is shown that merely elimination the fundamental frequency component on the dc side may not remove this dc component. The impact of such control action at one converter on the other

A. M. Gole; R. Verdolin; E. Kuffel

1995-01-01

117

Security assessment of DC zonal naval-ship power system  

Microsoft Academic Search

Security assessment of naval-ship power system under different fault conditions is important for real time operation of naval-ship power system. The existing indices of security assessment did not incorporate the probability of disturbances: therefore this paper proposes a probabilistic security assessment index. As the naval ship architecture is integrated with DC zonal distribution, then a special power flow analysis is

J. A. Momoh; S. S. Kaddah; W. Salawu

2001-01-01

118

Power Quality Issues on DC-Bus-Connected Photovoltaic System  

Microsoft Academic Search

Monitoring and diagnosis of power quality is an important aspect in studies pertaining to the performance of a photovoltaic (PV) system. This research analyzes the role of a mixed snubber circuit in reducing the conducted electromagnetic interference (EMI) emissions on a charge controller of a low power, standalone, PV system connected to a common DC bus. The mixed snubber circuit

C. Krishna Kumar; A. Nirmal Kumar

2012-01-01

119

Uprated dc power system and thermalhydraulic facilities at Columbia University  

Microsoft Academic Search

The necessity of carrying out large scale nuclear thermalhydraulic simulations is increasing. Such experiments call for large power sources, and to meet those requirements the dc power system at the Heat Transfer Research Facility of Columbia University has been upgraded to 11.5 MW. The uprated system, its installations, various subsystems, and operations are described. The thermalhydraulic loops and their auxiliary

W. E. Hovemeyer; S. R. Sreepada; J. E. Casterline

1978-01-01

120

DC zonal electrical system fault isolation and reconfiguration  

Microsoft Academic Search

Fault isolation and re-configuration on a DC bus distributed through an electrical system is studied. This paper builds upon previously proposed zonal architectures that ensure power continuity during a fault and isolation of a fault with minimal impact to un-faulted portions of the system. The approach utilizes no load switches for fault isolation aided by multiple power electronic converters feeding

Rob Cuzner; Aaron Jeutter

2009-01-01

121

A Testing System for Diagnosing Misconceptions in DC Electric Circuits.  

ERIC Educational Resources Information Center

Outlines a test-based diagnosis system for misconceptions in DC electric circuits and its three parts: problem library, problem selector and diagnoser. Discusses misconception discrimination and diagnosis theories, and reports the system supports satisfactory diagnosis. Includes an analysis of nine student misconceptions about electrical circuits…

Chang, Kuo-En; Liu, Sei-Hua; Chen, Sei-Wang

1998-01-01

122

3X DC-DC Multiplier\\/Divider for HEV Systems  

Microsoft Academic Search

This paper presents a bidirectional 3X dc-dc multiplier\\/divider that can interface the battery with the inverter dc bus for hybrid electric vehicle (HEV) traction drives. Compared with traditional multi-level dc-dc converter, this converter can have three output\\/input voltage ratios with smooth transition. The control method to limit the transient inrush current, as well as a novel regenerative clamping circuit for

Wei Qian; Fang Z. Peng; Miaosen Shen; Leon M. Tolbert

2009-01-01

123

Fly-by-Wire Systems Enable Safer, More Efficient Flight  

NASA Technical Reports Server (NTRS)

Using the ultra-reliable Apollo Guidance Computer that enabled the Apollo Moon missions, Dryden Flight Research Center engineers, in partnership with industry leaders such as Cambridge, Massachusetts-based Draper Laboratory, demonstrated that digital computers could be used to fly aircraft. Digital fly-by-wire systems have since been incorporated into large airliners, military jets, revolutionary new aircraft, and even cars and submarines.

2012-01-01

124

Flat-top system of the DC-280 cyclotron  

NASA Astrophysics Data System (ADS)

The flat-top cavity of the radio-frequency accelerating system designed at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, for the DC-280 cyclotron is described. The cyclotron is intended for increasing the capabilities and efficiency of experiments on the synthesis of super-heavy elements and an investigation of their nuclear physical and chemical properties. The DC-280 isochronous heavy-ion cyclotron will produce accelerated beam of ions in the range from neon to uranium. The parameters, design, and results of the experimental and 3D computer modeling of the flat-top cavity of the RF accelerating system of the DC-280 cyclotron are reported.

Gulbekyan, G. G.; Buzmakov, V. A.; Zarubin, V. B.; Ivanenko, I. A.; Kazarinov, N. Yu.; Karamysheva, G. A.; Franko, I.

2013-07-01

125

Lead-Oxygen DC Power Supply System.  

National Technical Information Service (NTIS)

A pollution-free, closed-loop electrical power system using a lead-oxygen battery to supply power for lightweight vehicles is described. The battery system is completely sealed and no outgassing occurs during operation. The system consists of the lead-oxy...

W. J. Britz W. A. Boshers J. J. Kaufmann

1974-01-01

126

Cost effective system for connecting multiwire cables to printed wiring boards. Final report  

SciTech Connect

The high density wiring used on newer electronic devices requires an improved processing technique to eliminate wiring errors and difficulties in reworking assemblies. For example, one subassembly has three cables and three connectors containing approximately 130 wires that terminate on a printed wiring board (PWB). The board is approximately 50.8 mm wide by 101.6 mm long, contains about 20 components, and interconnects with 8 to 10 wires from other printed wiring assemblies (PWAs). A unique system flexible enough to meet present and future work requirements was developed. The Component Locator System usually is referred to as a Work Director at Bendix. The Work Director shows the exact location for installing the wire on the PWB and codes the Cable Scanner for the correct wire. The Cable Scanner then provides an audible signal when the operator touches the correct wire. This combination of Component Locator System and Cable Scanner eliminates the following operations: marking wires for identification; sorting marked wires when attaching to connectors; electrically checking wire number versus pin number; identifying wires by markings when installing them in the PWB; and determining the proper PWB hole location from a visual aid.

Lewis, F.H.

1980-03-01

127

Overshoot Damping Control of DC Current at Deblock in AC-DC Interconnected System with Externally Commutated Converters  

NASA Astrophysics Data System (ADS)

Deblock of AC-DC interconnected system with externally commutated converters generally adopts soft start which makes trigger delay angle about 90 degrees and starts DC voltage from about 0kV. High DC voltage, however, is possibly caused by relation between the deblock signal and AC voltage phase at the commutation start of converter, resulting to overdue current. Consequently, overshoot of DC current is generated and transient AC voltage sag is caused especially under the condition of relatively weak AC system. We resolved the generation mechanism of DC current overshoot at deblock. In addition, we reflected the mechanism in the control system of Higashi-Shimizu FC, and drew up overshoot damping control by EMTP simulation. Furthermore, we checked the effect of overshoot damping control at the commissioning test period and verified that result of measurement corresponded with EMTP simulation.

Kogiso, Keiji; Shimonosono, Takaaki

128

Selection and stability issues associated with a navy shipboard DC zonal electric distribution system  

Microsoft Academic Search

The US Navy is currently investigating the implementation of a DC zonal electric distribution system (DC ZEDS) for the next generation of surface combatant. In replacing the current AC radial distribution system, significant gains can be realized in terms of survivability, weight, manning and cost. DC ZEDS is predicated on having starboard and port DC buses feeding electrical zones delineated

John G. Ciezki; Robert W. Ashton

2000-01-01

129

AC/DC Power Systems with Applications for future Lunar/Mars base and Crew Exploration Vehicle  

NASA Technical Reports Server (NTRS)

ABSTRACT The Power Systems branch at JSC faces a number of complex issues as it readies itself for the President's initiative on future space exploration beyond low earth orbit. Some of these preliminary issues - those dealing with electric power generation and distribution on board Mars-bound vehicle and that on Lunar and Martian surface may be summarized as follows: Type of prime mover - Because solar power may not be readily available on parts of the Lunar/Mars surface and also during the long duration flight to Mars, the primary source of power will most likely be nuclear power (Uranium fuel rods) with a secondary source of fuel cell (Hydrogen supply). The electric power generation source - With nuclear power being the main prime mover, the electric power generation source will most likely be an ac generator at a yet to be determined frequency. Thus, a critical issue is whether the generator should generate at constant or variable frequency. This will decide what type of generator to use - whether it is a synchronous machine, an asynchronous induction machine or a switched reluctance machine. The type of power distribution system - the distribution frequency, number of wires (3- wire, 4-wire or higher), and ac/dc hybridization. Building redundancy and fault tolerance in the generation and distribution sub-systems so that the system is safe; provides 100% availability to critical loads; continues to operate even with faulted sub-systems; and requires minimal maintenance. This report descril_es results of a summer faculty fellowship spent in the Power Systems Branch with the specific aim of investigating some of the lessons learned in electric power generation and usage from the terrestrial power systems industry, the aerospace industry as well as NASA's on-going missions so as to recommend novel surface and vehicle-based power systems architectures in support of future space exploration initiatives. A hybrid ac/dc architecture with source side and load side redundancies and including emergency generators on both ac and dc sides is proposed. The generation frequency is 400 Hz mostly because of the technology maturity at this frequency in the aerospace industry. Power will be distributed to several ac load distribution buses through solid state variable speed, constant frequency converters on the ac side. A segmented dc ring bus supplied from ac/dc converters and with the capability of connecting/disconnecting the segments will supply power to multiple de load distribution buses. The system will have the capability of reverse flow from dc to ac side in the case of an extreme emergency on the main ac generation side.

Chowdhury, Badrul H.

2005-01-01

130

Soft blocking of the dc term in Fourier optical systems  

Microsoft Academic Search

A technique utilizing an electron-trapping (ET) film to block the extended dc term in a Fourier optical system film is proposed and demonstrated. Since the blocking process is actually based on the subtracting property of the ET film, it is a soft blocking, which differs from, and is better than, simple hard blocking with a stop.

Suganda Jutamulia; Don A. Gregory

1998-01-01

131

Reversed diode earthing scheme in DC traction power system  

Microsoft Academic Search

Reducing rail voltage and stray current corrosion all at once is one of the challenging problems in DC electrified rail transit systems. Stray current is the main reason of corrosion in the metallic parts located in the proximity of the railway. Choosing appropriate earthing scheme is an effective way to decrease corrosion intensity and providing safety for personnel. This paper

M. M. Alamuti; A. Zare; M. Savaghebi

2008-01-01

132

Estimation of faults in DC electrical power system  

Microsoft Academic Search

This paper demonstrates a novel optimization-based approach to estimating fault states in a DC power system. The model includes faults changing the circuit topology along with sensor faults. Our approach can be considered as a relaxation of the mixed estimation problem. We develop a linear model of the circuit and pose a convex problem for estimating the faults and other

Dimitry Gorinevsky; Stephen Boyd; Scott Poll

2009-01-01

133

Estimation of Faults in DC Electrical Power System  

Microsoft Academic Search

This paper demonstrates a novel optimization- based approach to estimating fault states in a DC power system. The model includes faults changing the circuit topology along with sensor faults. Our approach can be considered as a relaxation of the mixed estimation problem. We develop a linear model of the circuit and pose a convex problem for estimating the faults and

Dimitry Gorinevsky; Stephen Boyd; Scott Poll

134

Fault Analysis in DC Electric Railways Feeding System  

Microsoft Academic Search

Electric railways and mono-rails in Japan are operated by DC feeding systems. HSCB (high speed circuit breakers) are generally used for these electric installations. Recently, HSVCB (high speed vacuum circuit breakers) have been investigated. HSVCB makes current superimposed on fault current so that the current is forced to be zero and interrupts the current. HSVCB has an advantage such as

R. Ikeda; E. Kaneko

2006-01-01

135

The Scrip System of the D.C. Transit System, Washington, D.C.  

National Technical Information Service (NTIS)

In 1968, the rate of bus robberies in Washington, D.C. was more than twice that of the previous year. The problem reached its climax on May 17, 1968, when six bus robberies occurred within a five hour period and a driver was killed in a seventh attempted ...

1970-01-01

136

Research on BiDirectional DC-DC Converter For a Stand-Alone Photovoltaic Hybrid Energy Storage System  

Microsoft Academic Search

A novel stand-alone photovoltaic ultracapacitor\\/battery hybrid energy storage system is proposed. Compared with the traditional one, this system has high power density and high energy density, prolong the lifetime of battery, achieve the system more efficient and reliable etc. A digital control system for multiple-input bi-directional dc-dc converter is designed and implemented. Software and hardware implementation issuses are described .

Xie Jun; Zhang Xing; Zhang Chongwei; Wang Chengyue

2010-01-01

137

A new DC\\/DC converter for solid oxide fuel cell powered residential systems  

Microsoft Academic Search

A low-cost high-efficiency DC\\/DC converter for use in residential fuel cell applications is proposed in this paper. The converter must accept a low voltage, high current input from the fuel cells and convert the power to a high voltage output. This DC\\/DC converter uses several technologies to achieve the high-efficiency, low-cost goal, including zero-voltage switching, a unique parallel input \\/

Kyle Sternberg; Hongwei Gao

2008-01-01

138

A Purely Ultracapacitor Energy Storage System for Hybrid Electric Vehicles Utilizing a Microcontroller Based dc-dc Boost Converter  

Microsoft Academic Search

The design and testing of a purely ultracapacitor energy storage system for the improvement of hybrid electric vehicles is presented. The system utilizes two large ultracapacitor banks for energy storage and a dc-dc boost converter that is capable of supplying 8kW for voltage regulation. The system provides greater roundtrip efficiency over batteries, improves a vehicle's ability to recapture energy from

Erik J. Cegnar; Herb L. Hess; Brian K. Johnson

139

Electrostatic coalescence system with independent AC and DC hydrophilic electrodes  

DOEpatents

An improved electrostatic coalescence system is provided in which independent AC and DC hydrophilic electrodes are employed to provide more complete dehydration of an oil emulsion. The AC field is produced between an AC electrode array and the water-oil interface wherein the AC electrode array is positioned parallel to the interface which acts as a grounded electrode. The emulsion is introduced into the AC field in an evenly distributed manner at the interface. The AC field promotes drop-drop and drop-interface coalescence of the water phase in the entering emulsion. The continuous oil phase passes upward through the perforated AC electrode array and enters a strong DC field produced between closely spaced DC electrodes in which small dispersed droplets of water entrained in the continuous phase are removed primarily by collection at hydrophilic DC electrodes. Large droplets of water collected by the electrodes migrate downward through the AC electrode array to the interface. All phase separation mechanisms are utilized to accomplish more complete phase separation.

Hovarongkura, A. David (Arlington, VA); Henry, Jr., Joseph D. (Morgantown, WV)

1981-01-01

140

Electromagnetic Energy Harvesting Circuit With Feedforward and Feedback DC–DC PWM Boost Converter for Vibration Power Generator System  

Microsoft Academic Search

This paper presents an integrated vibration power generator system. The system consists of a mini electromagnetic vibration power generator and a highly efficient energy harvesting circuit implemented on a minute printed circuit board and a 0.35-mum CMOS integrated chip. By introducing a feedback control into the dc-dc pulsewidth modulation (PWM) boost converter with feedforward control, the energy harvesting circuit can

Xinping Cao; Wen-Jen Chiang; Ya-Chin King; Yi-Kuen Lee

2007-01-01

141

Harmonic elimination, reactive power compensation and load balancing in three-phase, four-wire electric distribution systems supplying non-linear loads  

Microsoft Academic Search

In this paper, a new control scheme of a three-phase active power filter (APF) is proposed to eliminate harmonics, to compensate reactive power and neutral currents and to remedy system unbalance, in a three-phase four-wire electric power distribution system, with unbalanced non-linear loads. The APF is realized using three single phase IGBT based PWM-VSI bridges with a common dc bus

Bhim Singh; Kamal Al-Haddad; Ambrish Chandra

1998-01-01

142

Plasmonic properties of the metallic nanosphere\\/thin wire system  

Microsoft Academic Search

The plasmon hybridization method [1] is applied to a metallic nanosphere positioned near an infinitely long metallic wire. The plasmon resonances of the sphere are found to be shifted and to depend on the polarization of the incident light. In the limit of a thin wire, a virtual state consisting of propagating low energy wire plasmons is induced. The state

Feng Hao; P. Nordlander

2006-01-01

143

A Laser-Wire System for the International Linear Collider  

SciTech Connect

A new laser-wire has been installed in the extraction line of the ATF at KEK. It aims at demonstrating that laser-wires can be used to measure micrometre scale beam size. In parallel, studies have been made to specify a laser suitable for the ILC laser-wires.

Delerue, N.; Dixit, S.; Gannaway, F.; Howell, D.; Qurshi, M.; Blair, G.; Boogert, S.; Boorman, G.; Driouichi, C.; Deacon, L.; Aryshev, A.; Karataev, P.; Terunuma, N.; Urakawa, J.; Brachmann, A.; Frisch, J.; Ross, M.; /Oxford U. /Royal Holloway, U. of London /KEK, Tsukuba /SLAC

2009-04-30

144

Multi-kw dc power distribution system study program  

NASA Technical Reports Server (NTRS)

The first phase of the Multi-kw dc Power Distribution Technology Program is reported and involves the test and evaluation of a technology breadboard in a specifically designed test facility according to design concepts developed in a previous study on space vehicle electrical power processing, distribution, and control. The static and dynamic performance, fault isolation, reliability, electromagnetic interference characterisitics, and operability factors of high distribution systems were studied in order to gain a technology base for the use of high voltage dc systems in future aerospace vehicles. Detailed technical descriptions are presented and include data for the following: (1) dynamic interactions due to operation of solid state and electromechanical switchgear; (2) multiplexed and computer controlled supervision and checkout methods; (3) pulse width modulator design; and (4) cable design factors.

Berkery, E. A.; Krausz, A.

1974-01-01

145

Development of a 55 kW 3X dc-dc converter for HEV systems  

Microsoft Academic Search

The design of a 55 kW 3X dc-dc converter is presented for hybrid electric vehicle (HEV) traction drives. It can interface the battery with the inverter dc bus with three output\\/input voltage ratios and have smooth transition in voltage ratio changes. By making use of the parasitic inductance, the size and weight of the converter are significantly reduced. Its magnetic-less

Wei Qian; Fang Z. Peng; Leon M. Tolbert

2009-01-01

146

Study on speeding performance of power propulsion system with the integration of AC and DC  

Microsoft Academic Search

In order to reduce the weight and size of vessel integrated power system (VIPS), the AC-DC integrated propulsion system was studied. The system mainly consists of double winding synchronous generators (DWSG) and the DC propelling motor. DWSG supplies both AC and DC power simultaneously. The mathematic models of the main components were presented. Expressions for DWSG and the computation method

Guan Tao; Fu Li-jun; Ji Feng; Xie Zhen

2009-01-01

147

Phase Lock-In Reflectometry for Detection and Characterization of Wiring System Faults  

NASA Astrophysics Data System (ADS)

This paper describes the preliminary stage in the development of a Phase Lock-in Reflectometry (PLR) technique for detecting, locating and characterizing faults in electrical wiring systems. Results from the more-traditional techniques, e.g. Time-Domain Reflectometry (TDR) and Frequency-Domain Reflectometry (FDR) for detection and location of wiring-system faults are presented and compared with results from the PLR technique. The potential of PLR for characterizing wiring-system faults is briefly discussed. A methodology for combining wiring system models with experimental results to improve the characterization of faults as well as to improve the fundamental understanding of failure mechanisms is also presented.

Ambalam, Harikrishna; Reibel, Richard; Sathish, Shamachary; Frock, Brian

2006-03-01

148

Master–Slave Current-Sharing Control of a Parallel DC–DC Converter System Over an RF Communication Interface  

Microsoft Academic Search

Using analog wireless communication, we demonstrate a master-slave load-sharing control of a parallel dc-dc buck converter system, thereby eliminating the need for physical connection to distribute the control signal among the converter modules. The current reference for the slave modules is provided by the master module using radio-frequency (RF) transmission, thereby ensuring even sharing of the load current. The effect

Sudip K. Mazumder; Muhammad Tahir; Kaustuva Acharya

2008-01-01

149

Modelling, Simulation and Construction of a DC/DC Boost Power Converter: A School Experimental System  

ERIC Educational Resources Information Center

We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders…

Silva-Ortigoza, R.; Silva-Ortigoza, G.; Hernandez-Guzman, V. M.; Saldana-Gonzalez, G.; Marcelino-Aranda, M.; Marciano-Melchor, M.

2012-01-01

150

Automated visual inspection system for IC bonding wires using morphological processing  

NASA Astrophysics Data System (ADS)

This paper discusses an automated visual inspection system for IC bonding wires that uses high-contrast image capture and an accurate bonding-ball measurement algorithm. On IC assembly lines visual inspection is vital to maintaining IC reliability. Wire bonding requires the automated evaluation of bonding quality to maintain productivity. Both bonding balls and wires must be inspected to evaluate bonding quality. We developed a bonding-ball measurement algorithm based on subpixel and morphological techniques and a wire inspection algorithm based on border following. The automated inspection system measures ball diameters to an accuracy within jim which corresponds to one-half pixel taking 0. 2 seconds to inspect a wire and ball. Paired with a wire bonder the inspection system configures a fully automatic bonding system.

Tsukahara, Hiroyuki; Nakashima, Masato; Sugawara, Takehisa

1991-02-01

151

Real-time DC injection measurement technique for transformerless PV systems  

Microsoft Academic Search

DC injection suppression is crucial for the transformerless PV systems. IEEE Std.929-2000 specifies that the PV systems shall not inject the dc current greater than 0.5% of the full rated output current. DC injection measurement is not only useful for evaluating whether a transformerless PV system meets IEEE standards, but also for the effective dc suppression with injecting an equal

Wang Baocheng; Guo Xiaoqiang; Gu Herong; Mei Qiang; Wu Weiyang

2010-01-01

152

Selective polarization of nuclear spins in a wire-like quantum Hall system  

SciTech Connect

Nuclear spins are polarized selectively in a mesoscopic wire-like quantum Hall system by using the fractional quantum Hall system at Landau level filling factor nu = 2/3. The nuclear spin polarized region is limited by setting the filling factor in the wire to 2/3, while leaving the filling factor in the bulk away from 2/3. The longitudinal relaxation rate of selectively polarized nuclear spins probes electron spin properties in the wire.

Kobayashi, Takashi; Sasaki, Satoshi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan); Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Kumada, Norio; Ota, Takeshi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan); Hirayama, Yoshiro [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); ERATO-JST Nuclear Spin Electronics Project, 468-15 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-0845 (Japan)

2010-01-04

153

DC Bus Regulation With a Flywheel Energy Storage System  

NASA Technical Reports Server (NTRS)

This paper describes the DC bus regulation control algorithm for the NASA flywheel energy storage system during charge, charge reduction and discharge modes of operation. The algorithm was experimentally verified with results given in a previous paper. This paper presents the necessary models for simulation with detailed block diagrams of the controller algorithm. It is shown that the flywheel system and the controller can be modeled in three levels of detail depending on the type of analysis required. The three models are explained and then compared using simulation results.

Kenny, Barbara H.; Kascak, Peter E.

2002-01-01

154

DECOUPLED AC\\/DC LOAD FLOW FOR MONTE CARLO SIMULATION OF METRO POWER SYSTEM  

Microsoft Academic Search

Railway power system planners and operators need a tool for testing their designs or new timetables. This paper presents a tool for the DC traction systems, an algorithm called decoupled AC\\/DC load flow. The main feature of this algorithm is to separate the solution of AC and DC equations. Therefore, a minimum number of iterations is needed to avoid any

A. DER MINASSIANS; G. B. GHAREHPETIAN

155

Transient stability analysis of ac-dc power systems  

NASA Astrophysics Data System (ADS)

A non-linear model of a combined high-voltage ac-dc power system was digitally simulated. The model is used for the study and prediction of the effects of transient interactions between a high-voltage-direct-current (HVDC) transmission line and turbine-generator-shaft torsional behavior when the system is subjected to large disturbances. Improvement of a-c line loadability due to the stabilizing influence of a HVDC link was also examined. Turbine-generator torsional interaction studies were based on subsynchronous phenomena requiring an evaluation of the frequency, magnitude and decay of the subsynchronous currents in the ac-dc system following major system disturbances. The complex waveform of subsynchronous current, obtained by digital simulation, was analyzed using the Fast FOURIER Transform technique. Results demonstrate that a HVDC link can affect the incidence of turbine-generator torsionals, can significantly improve the stability of the system in general and can be used to effect increased loadability of the a-c lines.

Teshome, A.

1980-12-01

156

Solid state power systems for DC and RF accelerators  

NASA Astrophysics Data System (ADS)

Modern accelerator applications require high average and peak powers-particularly RF accelerators and DC accelerators. In many of these applications, it is possible to replace tubes in the power systems with solid state power supplies. In this paper we outline work which we have performed in developing solid state pulsed and CW pulsed power systems for RF linacs and for DC accelerators. We have built and successfully tested a 125 kV, 2.5 MW peak, 60 kW average pulsed power system which is well suited to driving ion beam linacs. This system is modular, with 3 modules capable of driving a large Klystron. The system has been extensively tested with both resistive and fault loads. This type of power supply promises to be less than half as expensive as a conventional thyratron modulator, with considerably more flexibility in pulse duration. We have also powered our Nested High Voltage (NHV) accelerators with a solid state power supply using IGBTs. This type of supply is suitable for both NHV machines, and other Dynamitron style accelerators. Pulsed burst mode excitation of this type of power supply allows us to maintain 1 MV in the NHV accelerator with less than three hundred watts of idling power.

Adler, R. J.; Richter-Sand, R. J.

1999-06-01

157

Model-based testability assessment and directed troubleshooting of shuttle wiring systems  

NASA Astrophysics Data System (ADS)

As the space shuttle ages, it is experiencing wiring degradation problems, including arcing, chaffing, insulation breakdown and broken conductors. A systematic and comprehensive test process is required to thoroughly test and QA the wiring systems. The NASA Wiring Integrity Reseach (WIRe) team recognized the value of a formal model based analysis for risk assessment and fault coverage analysis using our TEAMS toolset and commissioned a pilot study with QSI to explore means of automatically extracting high fidelity multisignal models from wiring information databases. The MEC1 Shuttle subsystem was the subject of this study. The connectivity and wiring information for the model was extracted from a Shuttle Connector Analysis Network (SCAN) electronic wirelist. Using this wirelist, QSI concurrently created manual and automatically generated wiring models for all wire paths associated with connector J3 on the MEC1 assembly. The manually generated model helped establish the rules of modeling. The complete MEC1 model was automatically generated based on these rules, thus saving significant modeling cost. The methodology is easily extensible to the entire shuttle wiring system. This paper presents our modeling and analysis results from the pilot study along with our proposed solutions to the complex issues of wiring integrity assessment problem.

Deb, Somnath; Domagala, Chuck; Shrestha, Roshan; Malepati, Venkatesh N.; Cavanaugh, Kevin F.; Patterson-Hine, Ann; Sanderfer, Dwight; Cockrell, Jim

2001-07-01

158

Multi-KW dc distribution system technology research study  

NASA Technical Reports Server (NTRS)

The Multi-KW DC Distribution System Technology Research Study is the third phase of the NASA/MSFC study program. The purpose of this contract was to complete the design of the integrated technology test facility, provide test planning, support test operations and evaluate test results. The subjet of this study is a continuation of this contract. The purpose of this continuation is to study and analyze high voltage system safety, to determine optimum voltage levels versus power, to identify power distribution system components which require development for higher voltage systems and finally to determine what modifications must be made to the Power Distribution System Simulator (PDSS) to demonstrate 300 Vdc distribution capability.

Dawson, S. G.

1978-01-01

159

Efficient Design in a DC to DC Converter Unit  

NASA Technical Reports Server (NTRS)

Space Flight hardware requires high power conversion efficiencies due to limited power availability and weight penalties of cooling systems. The International Space Station (ISS) Electric Power System (EPS) DC-DC Converter Unit (DDCU) power converter is no exception. This paper explores the design methods and tradeoffs that were utilized to accomplish high efficiency in the DDCU. An isolating DC to DC converter was selected for the ISS power system because of requirements for separate primary and secondary grounds and for a well-regulated secondary output voltage derived from a widely varying input voltage. A flyback-current-fed push-pull topology or improved Weinberg circuit was chosen for this converter because of its potential for high efficiency and reliability. To enhance efficiency, a non-dissipative snubber circuit for the very-low-Rds-on Field Effect Transistors (FETs) was utilized, redistributing the energy that could be wasted during the switching cycle of the power FETs. A unique, low-impedance connection system was utilized to improve contact resistance over a bolted connection. For improved consistency in performance and to lower internal wiring inductance and losses a planar bus system is employed. All of these choices contributed to the design of a 6.25 KW regulated dc to dc converter that is 95 percent efficient. The methodology used in the design of this DC to DC Converter Unit may be directly applicable to other systems that require a conservative approach to efficient power conversion and distribution.

Bruemmer, Joel E.; Williams, Fitch R.; Schmitz, Gregory V.

2002-01-01

160

Power Sharing Control between Load-Side Inverters in DC Microgrid for Super High Quality Electric Power Distribution System  

Microsoft Academic Search

DC microgrid is a novel power system using dc distribution in order to provide a super high quality electric power. The dc distribution system is suitable for dc output type distributed generations such as photovoltaic and fuel cells, and energy storages such as batteries and electric double layer capacitors. Power is distributed through dc distribution line and converted to required

Hiroaki Kakigano; Kaho Nada; Yushi Miura; Toshifumi Ise; Ryohei Uchida

2008-01-01

161

An integrated system for setting the optimal parameters in IC chip-package wire bonding processes  

Microsoft Academic Search

The wire bonding process is the key process in an IC chip-package. It is an urgent problem for IC chip-package industry to\\u000a improve the wire bonding process capability. In this study, an integrated system is proposed to identify and control parameters\\u000a in the wire bonding process in order to achieve high level performance and quality. First, an experimental design with

Tung-Hsu Hou; Shyh-Huei Chen; Tzu-Yu Lin; Kun-Ming Huang

2006-01-01

162

A control system for dc arc furnaces for power quality improvements  

Microsoft Academic Search

The dc arc furnaces are highly disturbing loads for transmission and distribution networks. The present paper proposes and implements an ac–dc converter control system for power quality improvements taking into account both flicker levels and harmonics at the point of common coupling. Different set of parameters for the proportional–integral controller are investigated for optimizing the dc arc furnace power quality

G. C. Lazaroiu; D. Zaninelli

2010-01-01

163

An overview of DC cable modelling for fault analysis of VSC-HVDC transmission systems  

Microsoft Academic Search

This paper analyzes dc cable transient modelling issues for voltage source converter (VSC) based high voltage direct current (HVDC) transmission systems, as proposed for large-scale renewable power integration, for example, offshore wind farms. Detailed dc cable models with different degrees of accuracy are analyzed for utilization in the analysis and simulations of dc fault conditions. This fault study is helpful

Jin Yang; John O'Reilly; John E. Fletcher

2010-01-01

164

High frequency acceleration system of the DC-280 cyclotron  

NASA Astrophysics Data System (ADS)

The radio-frequency (RF) accelerating system designed at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (FLNR JINR), for the DC-280 cyclotron is described. The cyclotron is intended to increase the capabilities and efficiency of experiments on the synthesis of superheavy elements and investigate their nuclear-physical and chemical properties. The DC-280 isochronous heavyion cyclotron will produce an accelerated beam of ions in the range from neon to uranium. The results of the preliminary and 3D numerical calculations of the main cavity of this system are reported. The preliminary calculations by the Coaxresonator software have allowed the geometry of the main cavity to be chosen. 3D numerical simulation has completely confirmed the correctness of the preliminary calculations. For example, the difference in frequency between the preliminary and 3D numerical calculations is no larger than 1%. The electric-field component maps obtained from the simulations are used to calculate the beam dynamics in the cyclotron.

Gulbekyan, G. G.; Zarubin, V. B.; Karamysheva, G. A.; Karamyshev, O. V.; Franko, J.

2012-12-01

165

A three-level DC-DC converter with wide-input voltage operations for ship-electric-power-distribution systems  

Microsoft Academic Search

This paper describes a newly developed three-level dc-dc converter with wide-input voltage operations for ship-electric-power-distribution systems. The proposed converter is designed with zero-voltage-switching (ZVS) techniques. The operational principles, design details and performances of the converter are discussed along with soft-switching characteristics through experimental results. Furthermore, design criteria on the dc-dc converter are focused on the minimization of the circulation current

Byeong-Mun Song; Robert McDowell; Andrew Bushnell; Joel Ennis

2004-01-01

166

A sliding wear tester for overhead wires and current collectors in light rail systems  

Microsoft Academic Search

This paper presents the dedicated experimental equipment developed for a study of the tribological behaviour of current collectors sliding against overhead contact wires under various conditions. A unique wear tester that replicates the operating conditions of actual pantographs in railway power collection systems was developed. The sliding element moves over the wire in a controlled horizontal motion at homogeneous velocity,

Da Hai He; Rafael Manory; Harry Sinkis

2000-01-01

167

Observational and experimental study of the lightning stroke attraction effect with ground wire system constructions  

Microsoft Academic Search

Although power distribution lines are protected by ground wire systems, there are fears that these ground wires may break at their corrosion points. For practical purposes, they have therefore been removed to avoid maintenance in certain areas. The Tokyo Electric Power Company (TEPCO) has continuously observed lightning strokes and obtained 321 datasets to date. The present study has determined the

Shuichi Oguchi; Tsunayoshi Ishii; Shigemitsu Okabe; Yoshiki Sakamoto; Masaki Tsuji; Akira Asakawa

2012-01-01

168

Application of Superconducting Power Cables to DC Electric Railway Systems  

NASA Astrophysics Data System (ADS)

For novel design and efficient operation of next-generation DC electric railway systems, especially for their substantial energy saving, we have studied the feasibility of applying superconducting power cables to them. In this paper it is assumed that a superconducting power cable is applied to connect substations supplying electric power to trains. An analysis model line was described by an electric circuit, which was analyzed with MATLAB-Simulink. From the calculated voltages and currents of the circuit, the regenerative brake and the energy losses were estimated. In addition, assuming the heat loads of superconducting power cables and the cryogenic efficiency, the energy saving of the total system was evaluated. The results show that the introduction of superconducting power cables could achieve the improved use of regenerative brake, the loss reduction, the decreased number of substations, the reduced maintenance, etc.

Ohsaki, Hiroyuki; Lv, Zhen; Sekino, Masaki; Tomita, Masaru

169

Low speed phaselock speed control system. [for brushless dc motor  

NASA Technical Reports Server (NTRS)

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

Fulcher, R. W.; Sudey, J. (inventors)

1975-01-01

170

Construction of 3-axis Coupling Wire rope model using MSC Adams and Analysis of the gimbals system's stabilization capacity  

Microsoft Academic Search

The stabilization system for observation is Forward Looking Infra-Red system that is attached to the vehicle using the wire rope isolator. Because the wire rope isolator is a nonlinear isolator, the capability of stabilization can't be estimated easily by simulation. So the analytical model of stabilization system applied the wire rope model is needed in process of development. In this

Hwan-Sic Kim; Ju-Seong Park; Sang-Ho Suh

171

A One Chip Hardened Solution for High Speed SpaceWire System Implementations. Session: Components  

NASA Technical Reports Server (NTRS)

An Application Specific Integrated Circuit (ASIC) that implements the SpaceWire protocol has been developed in a radiation hardened 0.25 micron CMOS technology. This effort began in March 2003 as a joint development between the NASA Goddard Space Flight Center (GSFC) and BAE Systems. The BAE Systems SpaceWire ASIC is comprised entirely of reusable core elements, many of which are already flight-proven. It incorporates a router with 4 SpaceWire ports and two local ports, dual PC1 bus interfaces, a microcontroller, 32KB of internal memory, and a memory controller for additional external memory use. The SpaceWire cores are also reused in other ASICs under development. The SpaceWire ASIC is planned for use on the Geostationary Operational Environmental Satellites (GOES)-R, the Lunar Reconnaissance Orbiter (LRO) and other missions. Engineering and flight parts have been delivered to programs and users. This paper reviews the SpaceWire protocol and those elements of it that have been built into the current and next SpaceWire reusable cores and features within the core that go beyond the current standard and can be enabled or disabled by the user. The adaptation of SpaceWire to BAE Systems' On Chip Bus (OCB) for compatibility with the other reusable cores will be reviewed and highlighted. Optional configurations within user systems and test boards will be shown. The physical implementation of the design will be described and test results from the hardware will be discussed. Application of this ASIC and other ASICs containing the SpaceWire cores and embedded microcontroller to Plug and Play and reconfigurable implementations will be described. Finally, the BAE Systems roadmap for SpaceWire developments will be updated, including some products already in design as well as longer term plans.

Marshall, Joseph R.; Berger, Richard W.; Rakow, Glenn P.

2007-01-01

172

Plasma chemistry in wire chambers  

SciTech Connect

The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.

Wise, J.

1990-05-01

173

Solar Cell Power Supply System for Composite Overhead Ground Wire Telecommunications Systems with Optical Fibers  

Microsoft Academic Search

This paper describes a solar cell power supply system designed for use with the optical repeaters used in ground wire telecommunications for ultra-high voltage overhead power transmission. Since it is difficult to assure commercial power availability for optical repeaters built near transmission towers, local power feeding is necessary. We considered the advantages and disadvantages of the following local power feeding

M. Ohara; K. Hanyuda; T. Suzuki; K. Watanabe

1985-01-01

174

Advanced medium-voltage bidirectional dc-dc conversion systems for future electric energy delivery and management systems  

NASA Astrophysics Data System (ADS)

The distributed renewable energy generation and utilization are constantly growing, and are expected to be integrated with the conventional grid. The growing pressure for innovative solutions will demand power electronics to take an even larger role in future electric energy delivery and management systems, since power electronics are required for the conversion and control of electric energy by most dispersed generation systems Furthermore, power electronics systems can provide additional intelligent energy management, grid stability and power quality capabilities. Medium-voltage isolated dc-dc converter will become one of the key interfaces for grid components with moderate power ratings. To address the demand of medium voltage (MV) and high power capability for future electric energy delivery and management systems, the power electronics community and industry have been reacting in two different ways: developing semiconductor technology or directly connecting devices in series/parallel to reach higher nominal voltages and currents while maintaining conventional converter topologies; and by developing new converter topologies with traditional semiconductor technology, known as multilevel converters or modular converters. The modular approach uses the well-known, mature, and cheaper power semiconductor devices by adopting new converter topologies. The main advantages of the modular approach include: significant improvement in reliability by introducing desired level of redundancy; standardization of components leading to reduction in manufacturing cost and time; power systems can be easily reconfigured to support varying input-output specifications; and possibly higher efficiency and power density of the overall system. Input-series output-parallel (ISOP) modular configuration is a good choice to realize MV to low voltage (LV) conversion for utility application. However, challenges still remain. First of all, for the high-frequency MV utility application, the low switching loss and conduction loss are must-haves for high efficiency, while bidirectional power flow capability is a must for power management requirement. To address the demand, the phase-shift dual-halfbridge (DHB) is proposed as the constituent module of ISOP configuration for MV application. The proposed ISOP DHB converter employs zero-voltage-switching (ZVS) technique combined with LV MOSFETs to achieve low switching and conduction losses under high frequency operation, and therefore high efficiency and high power density, and bidirectional power flow as well. Secondly, a large load range of high efficiency is desired rather than only a specific load point due to the continuous operation and large load variation range of utility application, which is of high importance because of the rising energy cost. This work proposes a novel DHB converter with an adaptive commutation inductor. By utilizing an adaptive inductor as the main energy transfer element, the output power can be controlled by not only the phase shift but also the commutation inductance, which allows the circulating energy to be optimized for different load conditions to maintain ZVS under light load conditions and minimize additional conduction losses under heavy load conditions as well. As a result, the efficiency at both light and heavy load can be significantly improved compared with the conventional DHB converter, and therefore extended high-efficiency range can be achieved. In addition, current stress of switch devices can be reduced. The theoretical analysis is presented and validated by the experimental results on a 50 kHz, 1 kW dc-dc converter module. Thirdly, input-voltage sharing and output-current sharing are critical to assure the advantages of the ISOP modular configuration. To solve this issue, an identically distributed control scheme is proposed in this work. The proposed control scheme, using only one distributed voltage loop to realize both input-voltage and output-current sharing, provides plug-and-play capability, possible high-level fault tolerance, and easy implementatio

Fan, Haifeng

175

Plasmonic properties of the metallic nanosphere/thin wire system.  

NASA Astrophysics Data System (ADS)

The plasmon hybridization method [1] is applied to a metallic nanosphere positioned near an infinitely long metallic wire. The plasmon resonances of the sphere are found to be shifted and to depend on the polarization of the incident light. In the limit of a thin wire, a virtual state consisting of propagating low energy wire plasmons is induced. The state is similar in nature to the virtual thin film state recently predicted and observed for a nanosphere near a thin metallic film [2]. [1] E. Prodan and P. Nordlander, J. Chem. Phys. 120(2004)5444-5454. [2] F. Le, N. Z. Lwin, J.M. Steele, M. Kall, N.J. Halas, and P. Nordlander, Nano Lett. 5(2005)2009-2013.

Hao, Feng; Nordlander, P.

2006-03-01

176

Development and Analysis of a Wire-Based Robot With Twin Direct-Drive Motor System  

NASA Astrophysics Data System (ADS)

In this paper, a sensorless wire rope tension control is introduced and analyzed to implement a wire-based robot with twin direct-drive motor system. Two of the same direct-drive motors are required and connected by wire rope mechanism. In the controller design, dual disturbance observers with respect to two control modes, namely the common mode and the differential mode are designed and applied for control of motion and wire rope tension. The wire rope tension in the common mode is controlled in order to regulate the mechanical bandwidth of the system. From the identification results, the high-tension of wire rope system is obtained a high mechanical bandwidth in the robot systems. The disturbance observer-based eliminates the need for the tension sensors, and may also be used to achieve the precise velocity and position control with the vibration-free performance in the differential mode. The effectiveness of the proposed method is verified by experimental results. It is shown that the high frequency responses are obtained by using high-tension of wire rope. The control performance may improve during the robot operation and, therefore, it is useful to compensate for the vibration effect.

Mitsantisuk, Chowarit; Ohishi, Kiyoshi; Urushihara, Shiro; Katsura, Seiichiro

177

Mass-asymmetry effects in coupled electron-hole quantum wire system  

NASA Astrophysics Data System (ADS)

The effect of mass-asymmetry on the ground-state of coupled electron-hole quantum wire system is investigated within the quantum version of the self-consistent mean-field approximation of Singwi, Tosi, Land, and Sjölander. The pair-correlation functions, static density susceptibility, and correlation energy are calculated over a range of wire parameters. We find that the mass-asymmetry affects appreciably both the intra- and inter-wire correlations, which in turn bring in a marked change in the e-h ground-state. Below a critical density, the e-h correlations now favor the liquid-Wigner crystal phase transition at a sufficiently large wire spacing. This result is in striking difference with the corresponding study on the mass-symmetric e-h wire model since here transition to the Wigner crystal phase occurs in the adequately close proximity of two wires at a much lower density, and there also occurs a crossover from Wigner to a charge-density-wave phase at relatively higher densities. We find that for a GaAs based e-h wire the critical density for Wigner crystallization is enhanced by a factor of about 2.6. As an important result, our theory captures nicely the recent experimental observation of Wigner crystallization in an un-equal density GaAs based e-h wire by Steinberg et al. [Phys. Rev. B 73, 113307 (2006)].

Moudgil, R. K.; Garg, Vinayak; Ahluwalia, P. K.

2010-04-01

178

Magnification of Starting Torques of DC Motors by Maximum Power Point Trackers in Photovoltaic Systems.  

National Technical Information Service (NTIS)

Direct current (dc) motors are used in terrestrial photovoltaic (PV) systems such as in water-pumping systems for irrigation and water supply. Direct current motors may also be used for space applications. Simple and low weight systems including dc motors...

J. Appelbaum S. Singer

1989-01-01

179

A reconfiguration algorithm for a DC Zonal Electric Distribution System based on graph theory methods  

Microsoft Academic Search

Modern DC power electric distribution system requires high stability under failure conditions. In general, the requirements of installed loads are nearly close to the maximum capacity supplied by a generator, and when a fault occurs produces an immediate change in the system topology. Therefore, DC power electric distribution system requires fast reconfiguration. This article presents an algorithm for network reconfiguration

Julia P. Certuche-Alzate; Miguel Vélez-Reyes

2009-01-01

180

Beam Emittance Measurement with Laser Wire Scanners in the ILC Beam Delivery System  

SciTech Connect

Accurate measurement of the beam phase-space is essential for the next generation of electron accelerators. A scheme for beam optics optimization and beam matrix reconstruction algorithms for the diagnostics section of the beam delivery system of the International Linear Collider based on laser-wire beam profile monitors are discussed. Possible modes of operation of the laser-wire system together with their corresponding performance are presented. Based on these results, prospects for reconstructing the ILC beam emittance from representative laser-wire beam size measurements are evaluated.

Agapov, I.; /CERN; Blair, G.A.; /Royal Holloway, U. of London; Woodley, M.; /SLAC

2008-02-01

181

Power system monitoring and source control of the Space Station Freedom DC power system testbed  

Microsoft Academic Search

Unlike a terrestrial electric utility which can purchase power from a neighboring utility, the Space Station Freedom (SSF) has strictly limited energy resources; as a result, source control, system monitoring, system protection, and load management are essential to the safe and efficient operation of the SSF Electric Power System (EPS). These functions are being evaluated in the DC Power Management

Greg L. Kimnach; Anastacio N. Baez

1992-01-01

182

Power system monitoring and source control of the Space Station Freedom dc-power system testbed  

Microsoft Academic Search

Unlike a terrestrial electric utility which can purchase power from a neighboring utility, the Space Station Freedom (SSF) has strictly limited energy resources; as a result, source control, system monitoring, system protection, and load management are essential to the safe and efficient operation of the SSF Electric Power System (EPS). These functions are being evaluated in the dc Power Management

Greg L. Kimnach; Anastacio N. Baez

1992-01-01

183

Research study on multi-KW-DC distribution system  

NASA Technical Reports Server (NTRS)

A detailed definition of the HVDC test facility and the equipment required to implement the test program are provided. The basic elements of the test facility are illustrated, and consist of: the power source, conventional and digital supervision and control equipment, power distribution harness and simulated loads. The regulated dc power supplies provide steady-state power up to 36 KW at 120 VDC. Power for simulated line faults will be obtained from two banks of 90 ampere-hour lead-acid batteries. The relative merits of conventional and multiplexed power control will be demonstrated by the Supervision and Monitor Unit (SMU) and the Automatically Controlled Electrical Systems (ACES) hardware. The distribution harness is supported by a metal duct which is bonded to all component structures and functions as the system ground plane. The load banks contain passive resistance and reactance loads, solid state power controllers and active pulse width modulated loads. The HVDC test facility is designed to simulate a power distribution system for large aerospace vehicles.

Berkery, E. A.; Krausz, A.

1975-01-01

184

75 FR 65052 - Consensus Standards, Standard Practice for Maintenance of Airplane Electrical Wiring Systems  

Federal Register 2010, 2011, 2012, 2013

...astm.org. To inquire about standard content and/or membership or about ASTM International Offices abroad, contact Daniel Schultz, Staff Manager for Committee F39 on Normal and Utility Category Airplane Electrical Wiring Systems: (610)...

2010-10-21

185

75 FR 65051 - Consensus Standards, Standard Practice for Inspection of Airplane Electrical Wiring Systems  

Federal Register 2010, 2011, 2012, 2013

...astm.org. To inquire about standard content and/or membership or about ASTM International Offices abroad, contact Daniel Schultz, Staff Manager for Committee F39 on Normal and Utility Category Airplane Electrical Wiring Systems: (610)...

2010-10-21

186

Partial Discharge Detection for Evaluation of Insulation Integrity in Aerospace Electric Power System Wiring and Components.  

National Technical Information Service (NTIS)

The paper describes the importance of partial discharge (PD) detection for aerospace electric power system wiring and components in low pressure environment. The relationships between recorded discharge pulse current waveforms and PD electrical characteri...

D. F. Grosjean D. G. Kasten D. L. Schweickart S. A. Sebo X. Liu

2006-01-01

187

Thin Wire Modeling for FDTD Electromagnetic Calculations in the Two-Dimensional Cylindrical Coordinate System  

NASA Astrophysics Data System (ADS)

In this paper, the equivalent radius of a thin wire represented using the FDTD method in the two-dimensional (2D) cylindrical coordinate system is identified as 0.135?r, where ?r is the lateral side length of the rectangular cells, while that of a thin wire represented in the 3D Cartesian coordinate system is known to be 0.230?r. Furthermore, it is shown that the technique proposed by Noda and Yokoyama to represent a thin wire having an arbitrary radius in the 3D Cartesian coordinate system can be applied successfully to representing such a thin wire in the 2D cylindrical coordinate system if 0.135?r is used for the equivalent radius instead of 0.230?r.

Taniguchi, Yohei; Baba, Yoshihiro; Nagaoka, Naoto; Ametani, Akihiro

188

A Theory of Control for a Class of Electronic Power Processing Systems: Energy-Storage DC-To-DC Converters. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

An analytically derived approach to the control of energy-storage dc-to-dc converters, which enables improved system performance and an extensive understanding of the manner in which this improved performance is accomplished, is presented. The control approach is derived from a state-plane analysis of dc-to-dc converter power stages which enables a graphical visualization of the movement of the system state during both steady state and transient operation. This graphical representation of the behavior of dc-to-dc converter systems yields considerable qualitative insight into the cause and effect relationships which exist between various commonly used converter control functions and the system performance which results from them.

Burns, W. W., III

1977-01-01

189

Identification of twin direct-drive motor system with consideration of wire rope tension  

Microsoft Academic Search

An adaptable stiffness of mechanical using wire rope tension control, called as a twin direct-drive motor system, has unique advantages in human-robot interaction system, when compared with conventional industrial robot. Since the wire rope is low friction and lightweight device, it is possible to achieve high-efficiency, high degree of reliability, and safety. In this paper, modeling and closed-loop identification of

Chowarit Mitsantisuk; Kiyoshi Ohishi; S. Urushihara; S. Katsura

2009-01-01

190

Optimal design of a soft-switched DC-DC converter for a prototype DC distribution system  

Microsoft Academic Search

With goals of increased littoral operation and reduced manning, future U.S. Naval surface combatants must employ new technologies and architectures that better enable the vessel to sustain battle damage and continue to fight effectively. Since the power system is integral to shipboard combat system and damage control operation, the U.S. Navy is investigating power electronics-based distribution topologies that enhance survivability

G. Ciezki; R. W. Ashton

2004-01-01

191

A generalized framework for sampled-data model analysis of closed-loop PWM DC-DC converter system  

Microsoft Academic Search

In spite of the fact that, sampled-data models of PWM DC power converter systems (PDCS) are more accurate and natural, little effort has been made to use sampled-data techniques for stability analysis and synthesis of closed-loop PDCS. Instead, averaged models are typically used for control loop design, while detailed simulations are used for validating closed-loop performances. Recent developments in sampled-data

Muhammad Mansoor Khan; Wu Zhi-Ming

2001-01-01

192

Power flow management strategies for a local DC Distribution System of More Electric Aircraft  

Microsoft Academic Search

The local DC Power Distribution System of More Electric Aircraft has to be able to sustain bidirectional power flow to and from electromechanical devices. Because the mechanical source (Turbine Engine) is unidirectional, some storage and dissipation systems are necessary to store or\\/and dissipate the returned energy to maintain the DC bus voltage to the reference value. Different power management strategies

He Zhang; Fabien MOLLET; Stefan BREBAN; Christophe SAUDEMONT; Benoît ROBYNS

2010-01-01

193

Transient overvoltages on a three terminal dc transmission system due to monopolar ground faults  

Microsoft Academic Search

Transient overvoltages have been investigated using the Electromagnetic Transients Program (EMTP) for a three-terminal dc transmission system. Pole to ground faults on a dc line were studied to investigate overvoltages on the healthy pole and also on the electrode lines. The effect of providing a metallic neutral conductor in one section of the three-terminal system was also studied, as was

G. T. Wrate; I. K. Tasinga; S. S. Low; D. J. Melvold; R. S. Thallam; D. W. Gerlach; J. Y. Chang

1990-01-01

194

Novel DC ring topology and protection system - a comprehensive solution for mega city power grids  

NASA Astrophysics Data System (ADS)

The development of mega cities leads to increased load concentration and brings additional challenges to managing the electrical grid while keeping power available for critical loads. Techniques using FACTS devices are being applied to alleviate power management difficulties and to confine faults in their originating areas in order to limit the risk of cascading failures in the grid. The addition of many FACTS devices often results in control and protection coordination difficulties, power oscillations between connected networks, subsynchronous resonance problems, and torsional interactions with nearby generator units. The most effective solution is obtained when the individual AC subsystems representing sources and loads are decoupled so a fault in a given subsystem is not propagated to another subsystem. This solution can be achieved by the deployment of a DC system where power sources and loads are connected to the DC bus through voltage source converters. For a mega city, this would be conceived as a DC ring feeding multiple loads and connected to remote and local power sources. Unfortunately, the lack of fast DC circuit breakers has been one of the key issues affecting extensive applications of DC systems with common DC buses; a DC fault would discharge all the capacitors of the DC bus and cause delays in system recovery and possibly a wide system collapse. In this research, I provide a comprehensive solution to mega city power grid problems by proposing a DC system topology that enables grid expansions without affecting existing protection settings or changing existing AC breaker ratings. I also propose the means for protecting the DC system by designing a fast DC breaker and developing a control algorithm capable of isolating DC faults without blocking converter stations or depleting DC bus capacitors. My contribution is three folds: (1) I modeled and simulated Shanghai power grid and performed a study to identify short circuit and voltage stability problems using data provided by ABB corporate research located in China. I built on the work that had been performed in ABB China by considering different contingencies and I applied solutions using individual FACTS devices such as FCL, SVC-LightRTM, and HVDC-LightRTM. I analyzed the results from each solution in order to assess its merits and limitations in dealing with fault current and voltage stability problems. Then I presented a novel DC ring topology that provides redundancy, better protection against cascading faults, and does not increase short circuit levels. With this topology, adding loads or power sources does not impact system protection or performance. (2) I proposed two novel designs for a DC circuit breaker that is of critical importance to DC applications using multiple converter stations. The proposed designs solve the problem of DC fault clearing without causing significant voltage drops, current oscillations, or shutting down of any converter station connected to the DC bus. The DC breaker rated at a voltage of 320 kV and a current of 3000 A can interrupt DC currents as high as 70 kA within 800 mus. (3) I proposed a novel placement of the DC circuit breakers within the DC ring topology combined with an intelligent protection algorithm that optimizes fault detection and isolation without affecting the rest of the DC system. The protection scheme uses local measurements and special coordination techniques for clearing solid faults and uses differential measurements to identify and isolate high impedance faults.

Haj-Maharsi, Mohamed Yassine

195

SEMICONDUCTOR INTEGRATED CIRCUITS: A variable step-down conversion ratio switched capacitor DC-DC converter for energy harvesting systems working in intermittent mode  

Microsoft Academic Search

Energy harvesting systems stimulate the development of power management for low power consumption applications. Improving the converter efficiency of power management circuits has become a significant issue in energy harvesting system design. This paper presents a variable step-down conversion ratio switched capacitor (SC) DC-DC converter to advance the converter efficiency of charge on the stored capacitor in a wireless monitoring

Hao Wenhan; Jia Chen; Chen Hong; Zhang Chun; Wang Zhihua

2009-01-01

196

Final Results of the Protected Superficial Femoral Artery Trial Using the FilterWire EZ System  

Microsoft Academic Search

The purpose of this study was to evaluate the safety and efficacy of debris-capture for distal protection using the FilterWire\\u000a EZ Embolic Protection System (Boston Scientific, Mountain View, CA) with the additional aim to further define the incidence\\u000a of distal embolization during superficial femoral artery (SFA) interventions. A prospective, single-centre registry was designed\\u000a to evaluate the performance of the FilterWire

Stefan Muller-HulsbeckTim; Tim H. Hümme; J. Philipp Schäfer; Nikolas Charalambous; Friedrich Paulsen; Martin Heller; Thomas Jahnke

2010-01-01

197

NASA requirements and applications environments for electrical power wiring  

Microsoft Academic Search

While a large data base for electrical arc track-resistant wire insulation exists for aircraft electrical power systems, comparable spacecraft-pertinent data are in limited supply. Existing insulation systems have been found to arc-track at potentials as low as 28 V dc. An account is presently given of the electrical, thermal, mechanical, and operational requirements for specification and testing of candidate wiring

Mark W. Stavnes; Ahmad N. Hammond

1992-01-01

198

Research on the modular multilevel converter applied to multi-terminal DC transmission system  

Microsoft Academic Search

The multi-terminal DC transmission (MTDC) is one of the development trends of the future grid, and the modular multilevel converter (MMC) had been confirmed that it suits for the multi-terminal DC transmission system. On the basis of predecessors' study, this paper introduces the structure of MMC, and the equations of MMC are summed up. Then, the basic modulation technologies of

Meng Liang; QinXiang Gao; Ya Fu

2011-01-01

199

Current and frequency range extension of AC-DC current tranfer difference measurement system at CMI  

Microsoft Academic Search

This paper describes current and frequency range extension of AC-DC current transfer difference measurement system in CMI which is now able to measure AC-DC current differences from 1 mA up to 10 A in the frequency range 10 Hz - 100 kHz.

V. Nováková Zachovalová; M. S?ira; J. Streit

2010-01-01

200

Development of Optical Fiber Current Transformer for DC Railway Power System  

Microsoft Academic Search

A novel DC current transformer (CT) based on the Faraday Effect has developed for DC railway power system. The advantages of the developed optical fiber CT are simple and light structure, easiness to handle and robustness to the external magnetic field caused by the adjacent electric current. The basic characteristics of the optical fiber CT are confirmed and compared with

Hitoshi Hayashiya; Tatsuya Kumagai; Takeshi Endo; Shinichi Hase; Masataka Akagi; Masami Hino

2006-01-01

201

Microprocessor-Controlled DC Motor for Load-Insensitive Position Servo System  

Microsoft Academic Search

The conventional proportional P controller has been often used as the position controller of the dc servo motor. When the unknown and inaccessible load torque, such as the coulomb friction, the gravity, and so on, is imposed on the dc servo motor, this control system has the steady-and\\/or transient-state error.

Kiyoshi Ohishi; Masato Nakao; Kouhei Ohnishi; Kunio Miyachi

1987-01-01

202

Adaptable DC offset correction  

NASA Technical Reports Server (NTRS)

Methods and systems for adaptable DC offset correction are provided. An exemplary adaptable DC offset correction system evaluates an incoming baseband signal to determine an appropriate DC offset removal scheme; removes a DC offset from the incoming baseband signal based on the appropriate DC offset scheme in response to the evaluated incoming baseband signal; and outputs a reduced DC baseband signal in response to the DC offset removed from the incoming baseband signal.

Golusky, John M. (Inventor); Muldoon, Kelly P. (Inventor)

2009-01-01

203

Study on nondestructive detection system based on x-ray for wire ropes conveyer belt  

NASA Astrophysics Data System (ADS)

A nondestructive detection system based on X-ray for wire ropes conveyer belt is designed by X-ray detection technology. In this paper X-ray detection principle is analyzed, a design scheme of the system is presented; image processing of conveyer belt is researched and image processing algorithms are given; X-ray acquisition receiving board is designed with the use of FPGA and DSP; the software of the system is programmed by C#.NET on WINXP/WIN2000 platform. The experiment indicates the system can implement remote real-time detection of wire ropes conveyer belt images, find faults and give an alarm in time. The system is direct perceived, strong real-time and high accurate. It can be used for fault detection of wire ropes conveyer belts in mines, ports, terminals and other fields.

Miao, Changyun; Shi, Boya; Wan, Peng; Li, Jie

2008-03-01

204

An Optimal Control Strategy for DC Bus Voltage Regulation in Photovoltaic System with Battery Energy Storage  

PubMed Central

This paper presents an evaluation of an optimal DC bus voltage regulation strategy for grid-connected photovoltaic (PV) system with battery energy storage (BES). The BES is connected to the PV system DC bus using a DC/DC buck-boost converter. The converter facilitates the BES power charge/discharge to compensate for the DC bus voltage deviation during severe disturbance conditions. In this way, the regulation of DC bus voltage of the PV/BES system can be enhanced as compared to the conventional regulation that is solely based on the voltage-sourced converter (VSC). For the grid side VSC (G-VSC), two control methods, namely, the voltage-mode and current-mode controls, are applied. For control parameter optimization, the simplex optimization technique is applied for the G-VSC voltage- and current-mode controls, including the BES DC/DC buck-boost converter controllers. A new set of optimized parameters are obtained for each of the power converters for comparison purposes. The PSCAD/EMTDC-based simulation case studies are presented to evaluate the performance of the proposed optimized control scheme in comparison to the conventional methods.

Daud, Muhamad Zalani; Mohamed, Azah; Hannan, M. A.

2014-01-01

205

An optimal control strategy for DC bus voltage regulation in photovoltaic system with battery energy storage.  

PubMed

This paper presents an evaluation of an optimal DC bus voltage regulation strategy for grid-connected photovoltaic (PV) system with battery energy storage (BES). The BES is connected to the PV system DC bus using a DC/DC buck-boost converter. The converter facilitates the BES power charge/discharge to compensate for the DC bus voltage deviation during severe disturbance conditions. In this way, the regulation of DC bus voltage of the PV/BES system can be enhanced as compared to the conventional regulation that is solely based on the voltage-sourced converter (VSC). For the grid side VSC (G-VSC), two control methods, namely, the voltage-mode and current-mode controls, are applied. For control parameter optimization, the simplex optimization technique is applied for the G-VSC voltage- and current-mode controls, including the BES DC/DC buck-boost converter controllers. A new set of optimized parameters are obtained for each of the power converters for comparison purposes. The PSCAD/EMTDC-based simulation case studies are presented to evaluate the performance of the proposed optimized control scheme in comparison to the conventional methods. PMID:24883374

Daud, Muhamad Zalani; Mohamed, Azah; Hannan, M A

2014-01-01

206

Brushless DC motor drive based on multi-input DC boost converter supplemented by hybrid PV\\/FC\\/battery power system  

Microsoft Academic Search

This paper describes a novel operation performance of a brushless DC motor (BLDC), fed by a Hybrid Distributed Generation System (HDGS). The HDGS is accompanied with photovoltaic (PV) array, fuel cell stacks and a battery to supply a fixed power for driving a BLDC motor. The HDGS employs a novel multi-input DC boost converter for utilizing DG sources in a

M. R. Feyzi; S. A. Kh. Mozaffari Niapour; F. Nejabatkhah; S. Danyali; A. Feizi

2011-01-01

207

Transient overvoltages on a three terminal dc transmission system due to monopolar ground faults  

SciTech Connect

Transient overvoltages have been investigated using the Electromagnetic Transients Program (EMTP) for a three-terminal dc transmission system. Pole to ground faults on a dc line were studied to investigate overvoltages on the healthy pole and also on the electrode lines. The effect of providing a metallic neutral conductor in one section of the three-terminal system was also studied, as was the sensitivity of the results to dc filter configuration and to neutral bus capacitance. It was found that the peak overvoltages for the dc line, specifically near the converter stations, are sensitive to the dc filter configuration. The overvoltages near the converter stations were also found to be affected by the neutral bus capacitance.

Wrate, G.T.; Tasinga, I.K.; Low, S.S.; Melvold, D.J. (Dept. of Water and Power, Los Angeles, CA (US)); Thallam, R.S.; Gerlach, D.W.; Chang, J.Y. (Salt River Project, Phoenix, AZ (USA))

1990-04-01

208

Turbulence Measurements by the DC-8 Meteorological Measurement System  

NASA Technical Reports Server (NTRS)

The instrumentation of a new MMS on the DC-8 aircraft is briefly described. Methods to compute and evaluate the turbulent dissipation rate epsilon, based on theory and MMS data, are discussed. Examples of turbulence measurements during encounters of a wake vortex, wave clouds, persistent contrails, mountain are gravity waves are illustrated.

Chan, K. R.; Dean-Day, J.; Bowen, S. W.; Bui, T. P.; Chan, K. Roland (Technical Monitor)

1997-01-01

209

An integrated dc-dc power converter for use in distributed generation power systems  

Microsoft Academic Search

Distributed generation (DG) power systems are becoming increasingly attractive as alternatives to traditional centralized power systems. Fuel cells are an important resource that can be used in such systems, but power electronic converter interfaces are needed to ensure that fuel cells can provide fixed and regulated output voltages as the output of a fuel cell can vary with load. Given

Pritam Das; Gerry Moschopoulos

2008-01-01

210

Implementation and control of grid connected AC-DC-AC power converter for variable speed wind energy conversion system  

Microsoft Academic Search

30 kW electrical power conversion system is developed for a variable speed wind turbine system. In the wind energy conversion system (WECS) a synchronous generator converts the mechanical energy into electrical energy. As the voltage and frequency of generator output vary along the wind speed change, a DC-DC boosting chopper is utilized to maintain constant DC link voltage. The input

Seung-Ho Song; Shin-il Kang; Nyeon-kun Hahm

2003-01-01

211

Dynamic stability analysis of PV-injected power into a parallel AC-DC power system  

Microsoft Academic Search

The paper introduces an approach to solve the problem of damping the electromechanical oscillations of conventional plant-photovoltaic generator hybrid system. The photovoltaic generator is coupled directly to the DC-link of AC-DC parallel connection to a large power system. The intermittent nature of the photovoltaic generator imposes an unpredictable characterization of negative load which affects the power system dynamic stability. The

F. M. A. Ghali; H. A. El-Khashab; M. S. Abdel-Motaleb

1994-01-01

212

Characterization and application of Shape Memory Alloy wires for micro and meso positioning systems  

NASA Astrophysics Data System (ADS)

The properties of Shape Memory Alloy (SMA) wires are determined by experimentation, and previously used experimental equipment contributes to measurement errors in data. In this study, various characterization experiments are designed and carried out using a precision characterization instrument for shape memory alloy wires to determine the properties and parameters of the alloy. These experiments demonstrate the behavior of SMA wires under different thermal and loading conditions as they occur in actuation applications. As SMA wires go through phase transformation, a significant amount of contraction force is produced. This actuation force has been used in bias spring actuators and differential actuators. In this dissertation, the force generated during the twinning of martensite is used to actuate positioning systems with small displacements at the micrometer level. A micropositioning system is designed and tested that has a positioning accuracy of about +/-0.15 mum. A relation between the current input and the displacement output is determined for the specific preload. The transformation force generated during the phase change from martensite to austenite is used as an actuation force for a second positioning system that uses linear bearing with a displacement range of about a millimeter. This positioning system actuated with a single nitinol wire and guided by symmetric parallel diaphragm flexures, was designed and tested. The actuation is repeatable to about +/-15 mum with variation of about +/-5 mum in postion at steady temperature.

Khan, Afzal

213

Strata reinforcement with bolting and wire-rope systems - a comparative study  

SciTech Connect

A strata reinforcement system which has been used on an experimental basis in some 60 Indian coal mines over the past 6 years is described. It consists of a system of 'rope stitching' in which wire rope is stretched across the roof of the roadway and the ends are grouted into 1.8 m drill holes. For spans exceedng 3.6 m, grouted bolts with eye hooks are used for additional reinforcement at mid-span. This paper presents the results of a model study to evaluate the relative reinforcement actions of wire-rope and bolting systems.

Raju, N.M.; Ghose, A.K.

1982-04-01

214

Combined Operation of AC and DC Distribution System with Distributed Generation Units  

NASA Astrophysics Data System (ADS)

This paper presents a DC distribution system which has been supplied by external AC systems as well as local DG units in order to demonstrate an overall solution to power quality issue. In this paper, the proposed operation method is demonstrated by simulation of power transfer between external AC systems, DG units, AC and DC loads. The power flow control in DC distribution system has been achieved by network converters and DG converters. Also, the mathematical model of the network, DG and load converters are obtained by using the average technique, which allows converter systems accurately simulated and control strategies for this converters is achieved. A suitable control strategy for network converters has been proposed that involves DC voltage droop regulator and novel instantaneous power regulation scheme. Also, a novel control technique has been proposed for DG converters. In this paper, a novel control system based on stationary and synchronously rotating reference frame has been proposed for load converters for supplying AC loads connected to the DC bus by balanced voltages. The several case studies have been studied based on proposed methods. The simulation results show that DC distribution systems including DG units can improve the power quality at the point of common coupling (PCC) in the power distribution system or industrial power system.

Noroozian, Reza; Abedi, Mehrdad; Gharehpetian, Gevorg

2010-07-01

215

Control design for multisource systems based on DC\\/DC converters duty cycle value  

Microsoft Academic Search

Purpose – The purpose of this paper is to describe a two-level hierarchical control strategy for electrical energy transfers in multisource renewable energy systems. The aim of the control design is to perform the energy transfers, according to the sources power variations and the load characteristics. Design\\/methodology\\/approach – The controller determines the operating mode of the multisource renewable energy system

Alioune Badara Mboup; François Guerin; Dimitri Lefebvre; Pape Alioune Ndiaye

2011-01-01

216

Control design for hybrid electrical energy systems based on dc\\/dc converters duty cycle value  

Microsoft Academic Search

This paper describes a two level hierarchical control strategy for electrical energy transfers in multisource renewable energy systems. The aim of the control design is to optimise the energy transfers, according to the sources power variations and the load characteristics. For this purpose, the controller determines the operating mode of the multisource renewable energy system and the power ratio provided

Alioune Badara Mboup; Pape Alioune Ndiaye; François Guerin; Dimitri Lefebvre

217

Identifier-based adaptive neural dynamic surface control for uncertain DC-DC buck converter system with input constraint  

NASA Astrophysics Data System (ADS)

In this paper, an identifier-based adaptive neural dynamic surface control (IANDSC) is proposed for the uncertain DC-DC buck converter system with input constraint. Based on the analysis of the effect of input constraint in the buck converter, the neural network compensator is employed to ensure the controller output within the permissible range. Subsequently, the constrained adaptive control scheme combined with the neural network compensator is developed for the buck converter with uncertain load current. In this scheme, a newly presented finite-time identifier is utilized to accelerate the parameter tuning process and to heighten the accuracy of parameter estimation. By utilizing the adaptive dynamic surface control (ADSC) technique, the problem of "explosion of complexity" inherently in the traditional adaptive backstepping design can be overcome. The proposed control law can guarantee the uniformly ultimate boundedness of all signals in the closed-loop system via Lyapunov synthesis. Numerical simulations are provided to illustrate the effectiveness of the proposed control method.

Chen, Qiang; Ren, Xuemei; Oliver, Jesus Angel

2012-04-01

218

A design and control of bi-directional non-isolated DC-DC converter for rapid electric vehicle charging system  

Microsoft Academic Search

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multiphase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is

Taewon Kang; Changwoo Kim; Yongsug Suh; Byungik Kang; Daegyun Kim

2012-01-01

219

Development of A 600 MHz wide bore (89 mm) NMR system using internal tin wires  

Microsoft Academic Search

Employing high performance internal-tin Nb3Sn superconducting wire in NMR superconducting magnets, it is possible to reduce NMR magnet system cost. A 600 MHz NMR magnet system with 89 mm room temperature bore has been designed, constructed and is being tested. The magnet and cryostat were designed to meet existing 600 MHz NMR superconducting magnet standards. The design involved extensive mechanical

Weijun Shen; M. Coffey; Wayne McGhee

2001-01-01

220

78 FR 1 - Prevailing Rate Systems; Abolishment of the Washington, DC, Special Wage Schedule for Printing...  

Federal Register 2010, 2011, 2012, 2013

...of the Washington, DC, Special Wage Schedule for Printing Positions AGENCY: U.S. Office of Personnel Management. ACTION...System special wage schedule for printing and lithographic positions. The final rule incorrectly listed the page number of...

2013-01-02

221

Transient current measurement of improved AC\\/DC current transformer for power system  

Microsoft Academic Search

The transient current measurement of the power system by an improved ac\\/dc current transformer is developed. The transient performance details and calculation formulas of the transformer are analyzed and derived. The important design bases for transient current measurement of the current transformer used to the power system are given. Testing results show that the transient error of 5000-A improved ac\\/dc

Shiyan Ren; Mingming Li; Xusheng Chen

1995-01-01

222

AC-DC current shunts and system for extended current and frequency ranges  

Microsoft Academic Search

This paper describes a new ac-dc current-shunt calibration system with a current range of 1 mA-100 A and a frequency range from 10 Hz to 100 kHz. The new system consists of an ac-dc comparator controlled via a universal serial bus and a set of reference coaxial shunts with dedicated thermal voltage converters. The design of the custom-built shunts has

Piotr S. Filipski; Michael Boecker

2006-01-01

223

AC-DC Current Shunts and System for Extended Current and Frequency Ranges  

Microsoft Academic Search

The paper describes a new ac-dc current shunt calibration system with a testing current range of 1 mA to 100 A and frequency range 10 Hz-100 kHz. The new system consists of a USB controlled ac-dc comparator and a set of reference coaxial shunts with dedicated thermal voltage converters. The design of custom build shunts has been optimized through theoretical

Piotr S. Filipski; Michael Boecker

2005-01-01

224

Wide-range ac \\/ dc earth leakage current sensor using fluxgate with self-excitation system  

Microsoft Academic Search

This paper describes an ac \\/ dc earth leakage current sensor using fluxgate magnetic sensor, which provides high sensitivity for wide-range current sensing. The fluxgate current sensor with self-excitation system can be used to detect small ac \\/ dc current of 10mA. Two kinds of detecting which pulse width and pulse frequency could be used in this system to achieve

Takahiro Kudo; Susumu Kuribara; Yasuhiro Takahashi

2011-01-01

225

A multilevel voltage-source converter system with balanced DC voltages  

Microsoft Academic Search

In this paper, a multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as back-to-back interconnection of power systems, large induction motor drives, and electrical traction drives. Multilevel voltage-source converters have a voltage unbalance problem in the DC capacitors. The problem may be solved by use of additional voltage regulators or separate DC sources. However, these solutions are

Fang Zheng Peng; Jih-Sheng Lai; John McKeever; James Vancoevering

1995-01-01

226

High-efficiency multiple-output DC-DC conversion for low-voltage systems  

Microsoft Academic Search

This versatile power converter controller provides dual outputs at a fixed switching frequency and can regulate either output voltage or target system delay (using an external - filter). In the voltage regulation mode, the output voltage is monitored with an analog-digital (A\\/D) converter, and the feedback compensation network is implemented digitally. The generation of the pulsewidth modulation (PWM) signal is

Abram P. Dancy; Rajeevan Amirtharajah; Anantha P. Chandrakasan

2000-01-01

227

A bidirectional DC-DC converter for fuel cell electric vehicle driving system  

Microsoft Academic Search

This paper presents a power converter for a fuel cell electric vehicle driving system. A new bidirectional, isolated topology is proposed in consideration of the differing fuel cell characteristics from traditional chemical-power battery and safety requirements. The studied converter has the advantages of high efficiency, simple circuit, and low cost. The detailed design and operating principles are analyzed and described.

Huang-Jen Chiu; Li-Wei Lin

2006-01-01

228

A novel safety system concept and implementation for implantable stimulators: A universal DC tissue leakage current detector  

Microsoft Academic Search

In this paper we describe a novel system concept and circuit implementation for detecting DC current leaking into tissue from implantable stimulators due to a fault. Such detection is critical as DC current passing into tissue from an electronic implant can cause permanent harm to the implant recipient. The proposed system detects any unintended DC current leaking into tissue regardless

Yashodhan Moghe; Torsten Lehmann

2008-01-01

229

Point of collapse methods applied to AC\\/DC power systems  

Microsoft Academic Search

The authors describe an extension of the point of collapse method developed for studies of AC systems to the determination of saddle-node bifurcations in power systems including high voltage direct current (HVDC) transmission. Bus voltage profiles are illustrated for an AC\\/DC test system. They significantly differ from the profiles of pure AC systems for typical system models. In particular, voltage

C. A. Canizares; Fernando L. Alvarado; Christopher L. DeMarco; Ian Dobson; Willis F. Long

1992-01-01

230

A system for the measurement of wire-rope defect positions  

Microsoft Academic Search

Electromagnetic tests are nowadays widely employed to early detect defects of metallic wire ropes. Commercial instruments for electromagnetic tests are able to highlight small defects but provide only a rough estimation of their positions. An analysis of the uncertainty contributions that affect the defect position measurements is described in this paper and an improved measurement system is also presented. The

A. Vallan

2004-01-01

231

Power quality improvement in three-phase four-wire systems using shunt active filters  

Microsoft Academic Search

This paper presents a shunt active filter control using the instantaneous power theory on a rotating reference frame for power quality improvement in 3-phase 4-wire system. By current space vector mapping on rotating reference frame, three linearly independent components are derived. The defined powers can be controlled by current vector components. The in-phase current vector component to voltage vector is

A. Esfandiari; M. Parniani; H. Mokhtari

2004-01-01

232

Wireless\\/Wired Collaborative Remote Consultation Emergency Healthcare Information Systems Framework  

Microsoft Academic Search

The paper presents an integrated, collaborative, distributed emergency healthcare information systems (HIS) framework over wireless, wired infrastructure in Taiwan. The framework can be extended and adapted to other regions as well. The Remote Consultation for Emergency Services (RCES) prototype based on the middleware technologies are proposed along with the feasible approaches. The prototype enhances the communication possibilities not only to

S. L. Hsieh; Y. C. Weng; S. H. Hsieh; F. P. Lai; K. P. Hsu; W. N. Tsai

2006-01-01

233

A photosensing system composed of photosystem I, molecular wire, gold nanoparticle, and double surfactants in water.  

PubMed

Photosensing performance of a system composed of photosystem I (PSI), vitamin K(1) (VK(1))-like molecular wire, and gold nanoparticles (AuNPs) in an aqueous solution was increased considerably by the addition of double surfactants, hexylamine and dodecylbenzenesulfonate. PMID:20449307

Miyachi, Mariko; Yamanoi, Yoshinori; Shibata, Yusuke; Matsumoto, Hirokazu; Nakazato, Kazuo; Konno, Masae; Ito, Kohsuke; Inoue, Yasunori; Nishihara, Hiroshi

2010-04-21

234

Testing of a flat conductor cable baseboard system for residential and commercial wiring  

NASA Technical Reports Server (NTRS)

The results of extensive testing (mechanical, electrical, chemical, environmental, thermal, and analytical) are reported for a flat conductor cable baseboard system for residential and commercial wiring. In all of the tests, Underwriters Laboratories (UL) Standards, UL Tentative Test Programs, or Accepted Engineering Practices were followed during test selection, test setup, and test accomplishment.

Hankins, J. D.

1974-01-01

235

Stability of large DC power systems using switching converters, with application to the International Space Station  

Microsoft Academic Search

A stability approach has been developed for the International Space Station PV power system, which is applicable to any large DC power system. It is based on establishing a set of phase and gain requirements at key subsystem interface points throughout the power system, which provide good confidence that the system will be stable under small signal conditions, with reasonable

E. W. Gholdston; K. Karimi; F. C. Lee; J. Rajagopalan; Y. Panov; B. Manners

1996-01-01

236

Electrical endurance of Co/Ni wire for magnetic domain wall motion device  

NASA Astrophysics Data System (ADS)

We investigated electrical endurance of perpendicularly magnetized Co/Ni wires, which are a promising candidate material system for current-induced domain wall motion device. Monitoring the wire resistance while applying dc stress is shown to be a promising way to evaluate the electrical breakdown. An electromigration model describes well the observed time-to-failure as a function of temperature and current density. The dc stress current density which leads to 10-yr lifetime with 50% failure at 150 °C was twice as large as the threshold current density for domain wall motion, suggesting that the device with Co/Ni wire is highly durable against electrical stresses.

Fukami, S.; Yamanouchi, M.; Honjo, H.; Kinoshita, K.; Tokutome, K.; Miura, S.; Ikeda, S.; Kasai, N.; Ohno, H.

2013-06-01

237

Investigation of AC\\/DC Resistance Ratios of Various Designs of Pipe-Type Cable Systems  

Microsoft Academic Search

Ac\\/dc resistance ratios of pipe-type cables are essential for the accurate determination of ampacity and power transmission capability. This Paper presents such measured and calculated data for large size compact segmental aluminum and tin and enamel coated copper conductor cables in carbon and stainless steel pipes. Ac\\/dc resistance ratios have also been determined for single cable per pipe systems. Measurements

D. A. Silver; G. W. Seman

1982-01-01

238

System and Method for Determining Rate of Rotation Using Brushless DC Motor  

NASA Technical Reports Server (NTRS)

A system and method are provided for measuring rate of rotation. A brushless DC motor is rotated and produces a back electromagnetic force (emf) on each winding thereof. Each winding's back-emf is squared. The squared outputs associated with each winding are combined, with the square root being taken of such combination, to produce a DC output proportional only to the rate of rotation of the motor's shaft.

Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

2000-01-01

239

Wavelet based method for fault detection in Medium Voltage DC shipboard power systems  

Microsoft Academic Search

This paper proposes a wavelet transform (WT) based multi-resolution analysis (MRA) method to obtain the features of different fault types in Medium Voltage DC (MVDC) shipboard power systems. DC topology is under consideration for future all-electric ships. One of the new challenges related to this architecture is fault detection. WT-based MRA method, as well as its properties, are studied and

Weilin Li; Min Luo; Antonello Monti; Ferdinanda Ponci

2012-01-01

240

Modular power distribution system to drive DC and AC electrical loads, in particular for vehicle or domotics application  

US Patent & Trademark Office Database

A modular power distribution system configured to drive DC and AC electrical loads comprises logical units in different locations receiving DC and AC power lines for distribution to respectively DC and AC electrical loads in all of these locations. In each of the logical units, the system comprises one or more physical units, and in each of the physical units one or more power modules for the distribution of DC or AC power to one of the DC or AC electrical loads. Finally, the system comprises at least one master control unit for each of the logical units placed in one of physical units to control the functions of the pertaining logical unit.

2013-05-14

241

Evolution of the Design of a Second Generation FireWire Based Data Acquisition System  

PubMed Central

Our laboratory has previously reported on the basic design concepts of an updated FireWire based data acquisition system for depth-of-interaction detector systems designed at the University of Washington. The new version of our data acquisition system leverages the capabilities of modern field programmable gate arrays (FPGA) and puts almost all functions into the FPGA, including the FireWire elements, the embedded processor, and pulse timing and integration. The design is centered around an acquisition node board (ANB) that includes 64 serial ADC channels, one high speed parallel ADC, FireWire 1394b support, the FPGA, a serial command bus and signal lines to support a rough coincidence window implementation to reject singles events from being sent on the FireWire bus. Adapter boards convert detector signals into differential paired signals to connect to the ANB. In this paper we discuss many of the design details, including steps taken to minimize the number of layers in the printed circuit board and to avoid skewing of parallel signals and unwanted bandwidth limitations.

Lewellen, T.K.; Miyaoka, R.S.; MacDonald, L.R.; Haselman, M.; DeWitt, D.; Hauck, S.

2011-01-01

242

Monitoring and data acquisition system for experimental general aviation fly?by?wire aircraft  

Microsoft Academic Search

A CAN data bus was used in a project of an experimental Fly?by?Wire control system (SPS?1) mounted on board a PZL?110 “Koliber” general aviation aircraft. This solution allows the free communication between flight control computers and individual modules of the system. The monitoring of the bus state and data frames is useful during particular hardware tests, system integration, laboratory and

P. Rzucid?o

2006-01-01

243

Analytical calculation of the RMS current stress on the DC-link capacitor of voltage-PWM converter systems  

Microsoft Academic Search

A simple analytical expression for the current stress on the DC-link capacitor caused by the load-side inverter of a voltage DC-link-converter system is derived. The DC-link capacitor- current RMS value is determined from the modulation depth and by the amplitude and the phase angle of the inverter output current assuming a sinusoidal inverter output current and a constant DC-link voltage.

J. W. Kolar; S. D. Round

2006-01-01

244

DC electrical conductivity study of cerium doped conducting glass systems  

NASA Astrophysics Data System (ADS)

The glass samples of composition 60V2O5-5P2O5-(35-x)B2O3-xCeO2, (1 <= x <= 5) were prepared by the conventional melt quench method. The samples were characterized by X-ray diffraction and thermo gravimetric-differential thermal analysis. The glass transition temperature and crystallization temperature determined from TG-DTA analysis. The DC electrical conductivity has been carried out in the temperature range 303-473 K. The maximum conductivity and minimum activation energy were found to be 0.039 Scm-1 and 0.15 eV at 473 K for x=1, respectively.

Barde, R. V.; Waghuley, S. A.

2013-06-01

245

A control of vehicle using steer-by-wire system with hardware-in-the-loop-simulation system  

Microsoft Academic Search

In this study, a steer-by-wire system is applied to a control vehicle. A SBW system is composed of two motors controlled by an ECU instead of mechanical linkage. Two motors follow general EPS system modeling. One motor in the steering wheel is to improve the driver's steering feed and the other motor in the steering linkage is to improve the

Seok-Hwan Jang; Tong-Jin Park; Chang-Soo Han

2003-01-01

246

A three-level DC-DC converter with wide-input voltage operations for ship-electric-power-distribution systems  

Microsoft Academic Search

This paper describes a newly developed 3-level DC-DC converter with wide-input voltage operations for ship-electric-power-distribution systems. The proposed converter is designed with zero-voltage-switching (ZVS) techniques. The operational principles, designs details and performance of the converter are discussed along with soft-switching characteristics and load transients through experimental waveforms. The converter achieved about 95% efficiency over wide 7kW load conditions.

Byeong-Mun Song; Robert McDowell; Andy Bushnell

2003-01-01

247

Research and Development of Aircraft Control Actuation Systems. The Development of a Direct Drive Fly-By-Wire Flight Control System and Evaluation of a Force Sharing Fly-By-Wire Actuator.  

National Technical Information Service (NTIS)

This report describes the design and test evaluation of a direct drive fly-by-wire redundant control system. Also included in the report is the evaluation testing of a fly-by-wire tandem actuator mechanization developed by Parker-Hannifin Aerospace Hydrau...

G. D. Jenney

1977-01-01

248

Computer simulation of a resonant dc link for advanced launch systems  

NASA Technical Reports Server (NTRS)

The performance of a resonant dc link based actuator power system being built for an advanced launch system application is evaluated for a typical launch scenario using two end-to-end system simulations, one using a digital computer and the other using a hybrid computer. Aspects of system performance from the switching of the power electronic devices to the vehicle aerodynamics are addressed. Using these simulations, it is shown that the resonance dc link actuator adequately stabilize the vehicle against a wind gust during a launch.

Sudhoff, S. D.; Wasynczuk, O.; Krause, P. C.; Kenny, B. H.

1993-01-01

249

DSP-based control of multi-rail DC-DC converter systems with non-integer switching frequency ratios  

Microsoft Academic Search

This paper examines the use of non-integer switching frequency ratios in digitally controlled DC-DC converters. In particular the execution of multiple control algorithms using a Digital Signal Processor (DSP) for this application is analyzed. The variation in delay from when the Analog to Digital Converter (ADC) samples the output voltage to when the duty cycle is updated is identified as

James Mooney; Simon Effler; Mark Halton; Abdulhussain E. Mahdi

2010-01-01

250

DC power transmission system of voltage source converter using pulse-interleaving auxiliary circuit  

US Patent & Trademark Office Database

A DC power transmission system of a voltage source converter using a pulse-interleaving auxiliary circuit is disclosed. The converter system comprises an IGBT converter for converting an AC power to a DC power or the DC power to the AC power; an open Y-Y transformer and a Y-.DELTA. transformer for stepping up or stepping down the AC power having a predetermined magnitude; a capacitor for dividing a DC voltage; and a DC Auxiliary circuit composed of a normal transformer and half-bridge for overlapping a pulse type input voltage to increase the number of pulses of an output waveform. In using a DC auxiliary circuit composed of normal transformer and 3-level half-bridge to increase the number of pulses of the output waveform by superposing the voltage in the form of the pulse, a normal transformer may be used instead of the tapped transformer to reduce the size thereof and to obtain an accurate transformer ratio, and a 3-level half-bridge may be used instead of the H-bridge to reduce the switching loss.

2009-03-03

251

Variable frequency controlled incremental conductance derived MPPT photovoltaic stand-along DC bus system  

Microsoft Academic Search

An incremental conductance (IC) derived MPPT PV stand-along dc bus system by constant-duty variable frequency control is proposed. Fast matching process to executing MPPT PV system is achieved by a simple control programming. The proposed PV system can provide enough energy to load as well as the battery charging with the residual energy. The feasibility is demonstrated by an example

Guan-Chyun Hsieh; Hung-Liang Chen; Yaohwa Chen; Chee-Ming Tsai; Shian-Shing Shyu

2008-01-01

252

Precision positioning of a DC-motor-driven aerostatic slide system  

Microsoft Academic Search

This paper deals with precision positioning in the presence of friction. The object studied is an aerostatic slide system driven by a DC motor with brushes that introduce friction to the system. For such systems, models that do not account for friction can only be used to describe the macrodynamic behavior. The microdynamic behavior is significantly different. Instead of designing

Junhong Mao; Hiroyuki Tachikawa; Akira Shimokohbe

2003-01-01

253

AC Versus DC Distribution SystemsDid We Get it Right?  

Microsoft Academic Search

We presently enjoy a predominantly AC electrical distribution system, the engineering basis for which was designed over 100 years ago. While AC distribution systems have served us well, we should periodically pause to assess what opportunities we have accepted or been denied by the overwhelming predominance of AC electrical power distribution systems. What opportunities could be obtained by engineering DC

Donald J. Hammerstrom

2007-01-01

254

Detection of birdcaging in steel wire rope of a hoisting winch system by analysis of load torque and stator current  

Microsoft Academic Search

The aim of this paper is to analyze theoretically and experimentally the stator current of a three phase induction machine and load torque signals in a hoisting winch system, in order to show how they are influenced by the wire rope faulty condition. When the wire rope is subjected to axial and torsional loads, the outer strands can separate from

H. Henao; S. M. J. Rastegar Fatemi; S. Sieg-Zieba; G. A. Capolino

2009-01-01

255

New Fault Location System for Power Transmission Lines Using Composite Fiber-Optic Overhead Ground Wire (OPGW)  

Microsoft Academic Search

This paper describes a new method of locating the section where an electrical fault occurs on a power transmission line using Composite Fiber-Optic Overhead Ground Wires (OPGWs). This fault location (FL) method locates the fault section by measuring the current induced in the ground wire (GW), i.e., OPGW in this system. The OPGW currents are measured at many towers which

K. Urasawa; K. Kanemaru; S. Toyota; K. Sugiyama

1989-01-01

256

New fault location system for power transmission lines using composite fiber-optic overhead ground wire (OPGW)  

Microsoft Academic Search

A new fault location (FL) method using composite fiber-optic overhead ground wires (OPGWs) is developed to find out where electrical faults occur on overhead power transmission lines. This method locates the fault section by detecting the current induced in the ground wire (GW), i.e. OPGW in this system. Since detected fault information is essentially uncertain, the new FL method treats

K. Urasawa; K. Kanemaru; S. Toyota; K. Sugiyama

1989-01-01

257

Feasibility study of a 270V dc flat cable aircraft electrical power distributed system  

Microsoft Academic Search

This report documents the efforts of a one man-year feasibility study to evaluate the usage of flat conductors in place of conventional round wires for a 270 volt direct current aircraft power distribution system. This study consisted of designing electrically equivalent power distribution harnesses in flat conductor configurations for a currently operational military aircraft. Harness designs were established for installation

M. J. Musga; R. J. Rinehart

1982-01-01

258

THE DESIGN OF FLY-BY-WIRE FLIGHT CONTROL SYSTEMS  

Microsoft Academic Search

The design of an advanced Flight Control System (FCS) is a technically challenging task for which a range of engineering disciplines have to align their skills and efforts in order to achieve a successful system design. This paper presents an overview of some of the factors, which need to be considered, and is intended to serve as an introduction to

Chris Fielding

259

Research on control strategy and bench test of automobile Steer-by-Wire system  

Microsoft Academic Search

Steering by Wire system is a revolution of steering system structure and function.lt cuts off the mechanical connection between steering wheel and steered wheels ,controls the steering motor to steer front wheels actively so as to improve handling and stabilities and active safety,and controls steering wheel motor to supply the driver with ideal road feel. First, driver-vehicle-road closed loop models

Yu Lei-yan; Qi Yao-guang; Liu Feng

2008-01-01

260

Analysis, simulation and control of DSTATCOM in three-phase, four-wire isolated distribution systems  

Microsoft Academic Search

This paper deals with the performance of distribution static synchronous compensator (DSTATCOM) connected to an alternator of 42.5 kVA rating feeding four-wire linear loads. Simulation of DSTATCOM connected such weak system is carried out using standard MATLAB environment and power system toolbox. Results are simulated for linear resistive-inductive lagging power-factor loads for power factor correction, voltage regulation and load balancing

B. Singh; A. Adya; A. P. Mittal; J. R. P. Gupta

2006-01-01

261

Flight-control system architecture optimization for fly-by-wire airliners  

Microsoft Academic Search

The design problem of a flight-control system on a large fly-by-wire airliner is to find combinations of actuator(s), power circuit(s), com- puter(s) for each movable, so as to fulfill the constraints imposed by the safety regulations, while keeping the resulting system weight as low as possible. The trend towards more electrical aircraft makes it harder and harder to determine, in

Christophe BAUERand; Kristen LAGADEC; Marcel MONGEAU

262

Lightweight, Low-Loss dc Transducer  

NASA Technical Reports Server (NTRS)

Direct current is measured by lightweight, magnetically coupled transducer that weighs only 4 grams, without actually being wired into circuit under test. Miniature dc transducer has five windings: 2 for ac excitation inputs, 2 for dc control inputs, and 1 for feedback. Wire gages are selected for minimum size and weight. Size and number of turns of dc windings are selected according to dc current range to be measured.

Nagano, S.; Koerner, T.; Brisendine, P.; Weiner, H.; Detwiler, R.

1982-01-01

263

Detection of High-Impedance Arcing Faults in Radial Distribution DC Systems  

NASA Technical Reports Server (NTRS)

High voltage, low current arcing faults in DC power systems have been researched at the NASA Glenn Research Center in order to develop a method for detecting these 'hidden faults', in-situ, before damage to cables and components from localized heating can occur. A simple arc generator was built and high-speed and low-speed monitoring of the voltage and current waveforms, respectively, has shown that these high impedance faults produce a significant increase in high frequency content in the DC bus voltage and low frequency content in the DC system current. Based on these observations, an algorithm was developed using a high-speed data acquisition system that was able to accurately detect high impedance arcing events induced in a single-line system based on the frequency content of the DC bus voltage or the system current. Next, a multi-line, radial distribution system was researched to see if the arc location could be determined through the voltage information when multiple 'detectors' are present in the system. It was shown that a small, passive LC filter was sufficient to reliably isolate the fault to a single line in a multi-line distribution system. Of course, no modification is necessary if only the current information is used to locate the arc. However, data shows that it might be necessary to monitor both the system current and bus voltage to improve the chances of detecting and locating high impedance arcing faults

Gonzalez, Marcelo C.; Button, Robert M.

2003-01-01

264

Places Wire  

NSDL National Science Digital Library

Are you curious to learn more about cities? You'd do well to make a beeline for the Places Wire site, which offers a cornucopia of material on urban parks, public policy, architecture, planning, and other topics. In sum total, the site is a "curated feed of news and commentary on architecture, landscape and urbanism." The site has partnered with 20 different organizations to provide new content on a daily basis. Some of the recent articles that have found their way to the site include "9 Suggestions for Changing DC's Height Limit" and "The Demise of the Public Hearing." Visitors can also use the drop-down View tab to scroll through the last few hours or days, as the content is quite dynamic. One gem that should not be missed is the archived appearance of Frank Lloyd Wright as a guest on the 1950s television program "What's My Line?"

265

High precision automated measuring system for AC-DC current transfer standards  

Microsoft Academic Search

An automated measuring system for AC-DC current transfer standards were developed at the Swedish National Testing and Research Institute (SP). The use of a guard makes intercomparisons with ppm precision possible at frequencies up to 100 kHz. Two multijunction thermal converters are used for evaluating the uncertainty of the system

Karl-Erik Rydler

1993-01-01

266

Low-Cost Undergraduate Control Systems Experiments Using Microcontroller-Based Control of a DC Motor  

ERIC Educational Resources Information Center

This paper presents low-cost experiments for a control systems laboratory module that is worth one and a third credits. The experiments are organized around the microcontroller-based control of a permanent magnet dc motor. The experimental setups were built in-house. Except for the operating system, the software used is primarily freeware or free…

Gunasekaran, M.; Potluri, R.

2012-01-01

267

Solar energy system performance evaluation, Forest City Dillon, Washington, DC, January 1981 through December 1981  

Microsoft Academic Search

The Forest City Dillon solar energy system is the Fort Lincoln Senior Village apartment complex in Washngton, DC. The active solar energy system is designed to supply 59% of the hot water, and consists of 2592 square feet of flat plate collectors, 3200-gallon storage tank, and an auxiliary oil-fired boiler. Performance data are given for each month of 1981 for

Pakkala

1981-01-01

268

Consideration for the malfunction of semiconductor circuit breaker in high voltage DC power supply system  

Microsoft Academic Search

This paper considers the malfunction mechanism of semiconductor circuit breaker in high voltage DC power supply system (HVDC). In HVDC system, the fast response breaker is required. Semiconductor circuit breaker is paid attention as one of the key technology in HVDC. However, in some condition, the semiconductor circuit is malfunctioned. When malfunction is happened, unexpected large current is flown to

Seiya Abe; Kentaro Fukushima; Sihun Yang; Mariko Ogawa; Kosuke Nomura; Masahito Shoyama; Tamotsu Ninomiya; Akira Matsumoto; Akiyoshi Fukui; Mikio Yamasaki

2010-01-01

269

Malfunction suppression of semiconductor circuit breaker in high voltage DC power supply system  

Microsoft Academic Search

In high voltage DC power supply system (HVDC) system, the fast response breaker is required. Semiconductor circuit breaker is paid attention as one of the key technology in HVDC. However, in some condition, the semiconductor circuit is malfunctioned. When malfunction occurs, unexpected large current is flown to the other normal line. In this paper, the malfunction suppression of semiconductor circuit

Seiya Abe; Sihun Yang; M. Ogawa; M. Shoyama; T. Ninomiya; Akira Matsumoto; Akiyoshi Fukui; Mikio Yamasaki

2010-01-01

270

Macroscopic quantum systems as measuring devices: dc SQUIDs and superselection rules  

Microsoft Academic Search

Using a Hilbert space formalism we present axiomatic models of both a current-fed thick superconducting ring and a dc SQUID (superconducting quantum interference device) as quantum systems possessing superselection rules. A method of quantization by parts is introduced to establish a quantum theory of a system having a circuit configuration. This involves separate quantization of parts of a circuit: the

F. E. Harrison; K. K. Wan

1997-01-01

271

Evaluating alternatives for integrating distributed DC generation with AC power systems  

Microsoft Academic Search

Distributed generation generally means on site electric power generation devices such as photovoltaics or fuel cells that are installed at the customer end of the electric power system. One complication is that the photovoltaic panel and the fuel cell generate direct current (DC) while the electric power system and thus existing end use equipment has been designed for alternating current

F. Wicks

2000-01-01

272

SEMICONDUCTOR INTEGRATED CIRCUITS: A variable step-down conversion ratio switched capacitor DC-DC converter for energy harvesting systems working in intermittent mode  

NASA Astrophysics Data System (ADS)

Energy harvesting systems stimulate the development of power management for low power consumption applications. Improving the converter efficiency of power management circuits has become a significant issue in energy harvesting system design. This paper presents a variable step-down conversion ratio switched capacitor (SC) DC-DC converter to advance the converter efficiency of charge on the stored capacitor in a wireless monitoring system of orthopedic implants. The converter is designed to work at 1 MHz switching frequency and achieves 15 to 2 V conversion. Measurement results show that the converter efficiency can reach 42% including all circuit power consumption, which is much higher than previous work.

Wenhan, Hao; Chen, Jia; Hong, Chen; Chun, Zhang; Zhihua, Wang

2009-12-01

273

Description of the SSF PMAD DC testbed control system data acquisition function  

NASA Technical Reports Server (NTRS)

The NASA LeRC in Cleveland, Ohio has completed the development and integration of a Power Management and Distribution (PMAD) DC Testbed. This testbed is a reduced scale representation of the end to end, sources to loads, Space Station Freedom Electrical Power System (SSF EPS). This unique facility is being used to demonstrate DC power generation and distribution, power management and control, and system operation techniques considered to be prime candidates for the Space Station Freedom. A key capability of the testbed is its ability to be configured to address system level issues in support of critical SSF program design milestones. Electrical power system control and operation issues like source control, source regulation, system fault protection, end-to-end system stability, health monitoring, resource allocation, and resource management are being evaluated in the testbed. The SSF EPS control functional allocation between on-board computers and ground based systems is evolving. Initially, ground based systems will perform the bulk of power system control and operation. The EPS control system is required to continuously monitor and determine the current state of the power system. The DC Testbed Control System consists of standard controllers arranged in a hierarchical and distributed architecture. These controllers provide all the monitoring and control functions for the DC Testbed Electrical Power System. Higher level controllers include the Power Management Controller, Load Management Controller, Operator Interface System, and a network of computer systems that perform some of the SSF Ground based Control Center Operation. The lower level controllers include Main Bus Switch Controllers and Photovoltaic Controllers. Power system status information is periodically provided to the higher level controllers to perform system control and operation. The data acquisition function of the control system is distributed among the various levels of the hierarchy. Data requirements are dictated by the control system algorithms being implemented at each level. A functional description of the various levels of the testbed control system architecture, the data acquisition function, and the status of its implementationis presented.

Baez, Anastacio N.; Mackin, Michael; Wright, Theodore

1992-01-01

274

A High Efficiency DC-DC Converter Topology Suitable for Distributed Large Commercial and Utility Scale PV Systems  

SciTech Connect

In this paper a DC-DC power converter for distributed photovoltaic plant architectures is presented. The proposed converter has the advantages of simplicity, high efficiency, and low cost. High efficiency is achieved by having a portion of the input PV power directly fed forward to the output without being processed by the converter. The operation of this converter also allows for a simplified maximum power point tracker design using fewer measurements

Mohammed S. Agamy; Maja Harfman-Todorovic; Ahmed Elasser; Robert L. Steigerwald; Juan A. Sabate; Song Chi; Adam J. McCann; Li Zhang; Frank Mueller

2012-09-01

275

Parametric excitation of dc current in a single-dot shuttle system via spontaneous symmetry breaking  

NASA Astrophysics Data System (ADS)

We investigate theoretically the dynamics of a spatially symmetric shuttle system subjected to an ac gate voltage. We demonstrate that in such a system parametric excitation gives rise to mechanical vibrations when the frequency of the ac signal is close to the eigenfrequency of the mechanical subsystem. These mechanical oscillations result in a dc shuttle current in a certain direction due to spontaneous symmetry breaking. The direction of the current is determined by the phase shift between the ac gate voltage and the parametrically excited mechanical oscillations. The dependence of the shuttle current on the dc gate voltage is also analyzed.

Peña-Aza, Milton E.; Scorrano, Alessandro; Gorelik, Leonid Y.

2013-07-01

276

Flying wires at Fermilab  

Microsoft Academic Search

Transverse beam profile measurement systems called flying wires have been installed and made operational in the Fermilab Main Ring and Tevatron accelerators. A flying wire is a device that passes (flies) a 25-?m carbon filament through a particle beam, transversely, at a constant velocity of between 2 and 5 m\\/s. Collisions between the beam particles and the wire produce secondary

J. Gannon; C. Crawford; D. Finley; R. Flora; T. Groves; M. MacPherson

1989-01-01

277

Design of a high voltage input - output ratio dc-dc converter dedicated to small power fuel cell systems  

NASA Astrophysics Data System (ADS)

Consuming chemical energy, fuel cells produce simultaneously heat, water and useful electrical power [J.M. Andújar, F. Segura, Renew. Sust. Energy Rev. 13, 2309 (2009)], [J. Larminie, A. Dicks, Fuel Cell Systems Explained, 2nd edn. (John Wiley & Sons, 2003)]. As a matter of fact, the voltage generated by a fuel cell strongly depends on both the load power demand and the operating conditions. Besides, as a result of many design aspects, fuel cells are low voltage and high current electric generators. On the contrary, electric loads are commonly designed for small voltage swing and a high V/I ratio in order to minimize Joule losses. Therefore, electric loads supplied by fuel cells are typically fed by means of an intermediate power voltage regulator. The specifications of such a power converter are to be able to step up the input voltage with a high ratio (a ratio of 10 is a classic situation) and also to work with an excellent efficiency (in order to minimize its size, its weight and its losses) [A. Shahin, B. Huang, J.P. Martin, S. Pierfederici, B. Davat, Energy Conv. Manag. 51, 56 (2010)]. This paper deals with the design of this essential ancillary device. It intends to bring out the best structure for fulfilling this function. Several dc-dc converters with large voltage step-up ratios are introduced. A topology based on a coupled inductor or tapped inductor is closely studied. A detailed modelling is performed with the purpose of providing designing rules. This model is validated with both simulation and implementation. The experimental prototype is based on the following specifications: the fuel cell output voltage ranges from a 50 V open-voltage to a 25 V rated voltage while the load requires a constant 250 V voltage. The studied coupled inductor converter is compared with a classic boost converter commonly used in this voltage elevating application. Even though the voltage regulator faces severe FC specifications, the measured efficiency reaches 96% at the rated power whereas conventional boost efficiency barely achieves 91.5% in the same operating conditions.

Béthoux, O.; Cathelin, J.

2010-12-01

278

D.C. Lamp Burn-Out Protection.  

National Technical Information Service (NTIS)

A D.C. lamp system having a number of small zener diodes arranged in electrical parallelism with various lamp current supply wires. The zener diodes are sized so that the collective wattage ratings of the zeners is equal to the arithmetical product of the...

S. Sawka V. Moretti S. Heal

1982-01-01

279

Passive obstacle detection system (PODS) for wire detection  

Microsoft Academic Search

Boeing has developed algorithms and processing to detect power lines and cables in passive imagery from a wide variety of different sources. The algorithm has been demonstrated with imagery from visible, medium and long wave infra-red (MWIR and LWIR), and Passive MilliMeter Wave (PMMW) sensors. Flight demonstrations of the real-time system have been performed with both visible and LWIR image

John N. Sanders-Reed; Dennis J. Yelton; Christian C. Witt; Ralph R. Galetti

2009-01-01

280

Passive Obstacle Detection System (PODS) for Wire Detection  

Microsoft Academic Search

Boeing has developed algorithms and processing to detect power lines and cables in passive imagery from a wide variety of different sources. The algorithm has been demonstrated with imagery from visible, medium and long wave infra-red (MWIR and LWIR), and Passive MilliMeter Wave (PMMW) sensors. Flight demonstrations of the real-time system have been performed with both visible and LWIR image

John N. Sanders-Reed; Dennis J. Yelton; Christian C. Witt; Ralph R. Galetti

281

DC current distribution mapping system of the solar panels using a HTS-SQUID gradiometer  

NASA Astrophysics Data System (ADS)

Solar panels are expected to play a major role as a source of sustainable energy. In order to evaluate solar panels, non-destructive tests, such as defect inspections and response property evaluations, are necessary. We developed a DC current distribution mapping system of the solar panels using a High Critical Temperature Superconductor Superconducting Quantum Interference Device (HTS-SQUID) gradiometer with ramp edge type Josephson junctions. Two independent components of the magnetic fields perpendicular to the panel surface (?Bz/?x, ?Bz/?y) were detected. The direct current of the solar panel is visualized by calculating the composition of the two signal components, the phase angle, and mapping the DC current vector. The developed system can evaluate the uniformity of DC current distributions precisely and may be applicable for defect detection of solar panels.

Miyazaki, Shingo; Kasuya, Syohei; Mawardi Saari, Mohd; Sakai, Kenji; Kiwa, Toshihiko; Tsukamoto, Akira; Adachi, Seiji; Tanabe, Keiichi; Tsukada, Keiji

2014-05-01

282

THE TRACK SYSTEM IN WASHINGTON, D.C.  

ERIC Educational Resources Information Center

THE FOUR AREAS PRESENTED ARE GROUP AND INDIVIDUAL INTELLIGENCE TESTS, ACHIEVEMENT TESTS, EDUCATIONAL GROUPING PROCEDURES, AND FACTORS ASSOCIATED WITH LOW INCOME. A TRACK SYSTEM, OR ANY SYSTEM OF GROUPING, SHOULD PROMOTE RATHER THAN HINDER THE ACHIEVEMENT OF BOTH THE LOW-INCOME GROUPS AND THE HIGHER-INCOME GROUPS. THE PRESENT TRACK SYSTEM IN…

BLACKE, EVIAS, JR.

283

Avian Hatching Monitor and Control System Based on 1Wire Sensor Groups  

Microsoft Academic Search

System selects temperature sensor DS18B20 and humidity sensor HS1101 to compose sensor groups after analyzing avian hatching requirement, which realizes temperature and humidity automatic monitor and control through 1-wire bus technology. Sensor groups complete field hatching temperature\\/ humidity monitor and transmit analog signal into digital signal, single chip microprocessor (SCM) AT89C51 as core controller processes it, drives actuators to realize

Wen Xinling

2008-01-01

284

NASA/BAE Systems SpaceWire Efforts  

NASA Technical Reports Server (NTRS)

This paper discusses the state of the NASA and BAE SYSTEMS developments using Spacewire. NASA has developed intellectual property that implements Spacewire in Register Transfer Level VHDL for a Spacewire link and router. This design has been extensively verified using directed tests from the Spacewire Standard and design specification, as well as being randomly tested to flush out hard to find bugs in the code. The high level features of the design will be discussed, including the support for multiple time code masters, which will be useful for the James Webb Space Telescope electrical architecture. This design is now ready to be targeted to FPGA's and ASICs. Target utilization and performance information will be presented for some spaceflight qualified FPGA's and a discussion of the ASIC implementations will be addressed. In particular, the BAE SYSTEMS ASIC will be highlighted which will be implemented in their 0.25 micron rad-hard line. The chip will implement a 4-port router with the ability to tie chips together to make larger routers without external glue logic. This part will have integrated LVDS driver/receivers, include a PLL and include skew control logic. It will be targeted to run at greater than 300 MHz and include the implementation for the proposed Spacewire transport layer. The need to provide a reliable transport mechanism for Spacewire has been identified by both NASA and ESA, who are attempting to define a transport layer standard that utilizes a low overhead, low latency connection oriented approach. The Transport layer needs to be implemented in hardware-to prevent bottlenecks.

Rakow, Glenn Parker; Schnurr, Richard G.; Kapcio, Paul

2003-01-01

285

Design of portable performance parameter test system for aviation DC generator  

Microsoft Academic Search

Aimed at the requirement of fast test for aviation DC generator, a portable performance parameters test system is introduced in this paper. According to the requirement of GJB181 and GJB181A, the hardware structure and software of test system are analyzed, and the design and implementation of the test system software with LabVIEW is completed. The system has the functions including

Shutuan Zhang; Fang Lu; Zhongshan Jiang; Kai Zhang

2009-01-01

286

Cable Bundle Wire Derating  

NASA Technical Reports Server (NTRS)

The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: 3.7 amps per wire, bundle of 15 or more wires, 70 C environment, and vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

Lundquist, Ray A.; Leidecker, Henning

1998-01-01

287

Cable Bundle Wire Derating  

NASA Technical Reports Server (NTRS)

The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire; (2) bundle of 15 or more wires; (3) 70 C environment: and (4) vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

Lundquist, Ray A.; Leidecker, Henning

1998-01-01

288

Monitoring of debris flows and landslides by wired and wireless systems. Experiences from the Catalan Pyrenees.  

NASA Astrophysics Data System (ADS)

Sophisticated monitoring of landslides for research purpose has started in the 1990thies in the Catalan Pyrenees. Since then several types of mass movements (large landslides, debris flows, shallow landslides and rock falls) and multiples techniques have been applied. In this contribution, special attention will be given to the debris-flow monitoring system installed since summer 2009 in the Rebaixader catchment, Central Pyrenees. The monitoring system has continuously been improved during the last years and nowadays includes devices studying the three major aspects: 1) initiation, 2) flow dynamics, and 3) accumulation. While some parts of the monitoring network include a traditional wired system, the newer parts were installed using low-power wireless devices. Two major aspects will be discussed. First, results of the Rebaixader monitoring site will be presented. Second, experience regarding the monitoring will be evaluated focussing on technical aspects and the comparison between wired and wireless techniques. In the Rebaixader catchment, 6 debris flows and 11 debris floods were observed between August 2009 and October 2012. Surprisingly, also 4 major rock falls were recorded. The rainfall analysis shows that the debris flows were triggered by short, high-intensity rainstorms with a preliminary threshold of about 15 mm during 1 hour. In addition, there was observed a positive trend between event volume and rainfall amount or intensity. The analysis of the ground vibration signals shows significant differences between the time series recorded at the different geophones. These differences are associated with the geophone location in the channel (distance and material), the mounting or the data acquisition system. For instance, the most downstream geophone, installed in bedrock, shows the clearest debris-flows vibration time series, while the uppermost is the most reliable regarding the detection of rockfalls. An evaluation of wired versus wireless monitoring systems shows that wireless techniques have several advantages. They are generally smaller and due to the wireless condition the selection of the sensor location is not restricted like in the standard wired systems. Additionally, they are simple to install and consume much less power. Importantly, they are also more competitive in terms of pricing versus traditional wired solutions. Nevertheless, the adoption of this new technology has not been straightforward due to the harsh conditions where sensors are usually deployed. The later delayed and complicated the installation of some sensors in the Rebaixader site but allowed us to improve the monitoring solution. Finally, some very recent experiences on the wireless sensor network installed in a shallow landslide in the Pre-Pyrenees confirmed that this technique is a perfect solution not only for monitoring, but also for warning systems.

Hürlimann, Marcel; Abancó, Clàudia; Moya, José; Vilajosana, Ignasi; Llosa, Jordi

2013-04-01

289

Wiring of Divergent Networks in the Central Auditory System  

PubMed Central

Divergent axonal projections are found throughout the central auditory system. Here, we evaluate these branched projections in terms of their types, distribution, and putative physiological roles. In general, three patterns of axon collateralization are found: intricate local branching, long-distance collaterals, and branched axons (BAs) involved in feedback-control loops. Local collaterals in the auditory cortex may be involved in local processing and modulation of neuronal firing, while long-range collaterals are optimized for wide-dissemination of information. Rarely do axons branch to both ascending and descending targets. Branched projections to two or more widely separated nuclei or areas are numerically sparse but widespread. Finally, branching to contralateral targets is evident at multiple levels of the auditory pathway and may enhance binaural computations for sound localization. These patterns of axonal branching are comparable to those observed in other modalities. We conclude that the operations served by BAs are area- and nucleus-specific and may complement the divergent unbranched projections of local neuronal populations.

Lee, Charles C.; Kishan, Amar U.; Winer, Jeffery A.

2011-01-01

290

Digital wires  

Microsoft Academic Search

We study hardware implementations of cellular automata as reliable, adjustable, and secure commication lines. We discuss energy efficient digital wires on a nano-scale, all-optical digital wires, and digital wires as power lines and present performance data of a prototype digital wire, a six cells wide and ten cells long Boolean network. We show that digital wires have the following advantages:

Alfred Hübler

2009-01-01

291

Multilevel voltage-source converter system with balanced dc voltages.  

National Technical Information Service (NTIS)

A multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as large induction motor drives, back-to-back interconnected power systems, and electrical traction drives. Multilevel voltage-source converters have a...

F. Z. Peng J. S. Lai J. McKeever J. VanCoevering

1995-01-01

292

Modified DSTATCOM Topology with Reduced DC Link Voltage for Reactive and Harmonic Power Compensation of Unbalanced Nonlinear Load in Distribution System  

NASA Astrophysics Data System (ADS)

This paper proposes a modified four-leg distribution static compensator (DSTATCOM) topology for compensation of unbalanced and nonlinear loads in three-phase four-wire distribution system. DSTATCOM, connected in parallel to the load, supplies reactive and harmonic powers demanded by unbalanced nonlinear loads. In this proposed topology, the voltage source inverter (VSI) of DSTATCOM is connected to point of common coupling (point of interconnection of source, load, DSTATCOM) through interface inductor and series capacitance, unlike the conventional topology which consists of interface inductor alone. Load compensation with a lower value of input DC link voltage of VSI is possible in this modified topology compared to conventional topology. A comparative study on modified and conventional topologies in terms of voltage rating of inverter power switches, switching losses in VSI and power rating of input DC capacitor of VSI is presented. The detailed design aspects of DC link capacitor and interface series capacitor are also presented. The reference filter currents are generated using instantaneous symmetrical component theory and are tracked using hysteresis current control technique. A detailed simulation study is carried out, to compare the compensation performances of conventional, modified topologies using PSCAD simulator and experimental studies are done to validate the simulation results.

Geddada, Nagesh; Karanki, Srinivas B.; Mishra, Mahesh K.

2014-06-01

293

SpaceWire-based thermal-infrared imager system for asteroid sample return mission HAYABUSA2  

NASA Astrophysics Data System (ADS)

A thermal-infrared (TIR) imager system is developed for HAYABUSA2, which is planned to be launched in 2014 and aims at sample-return from a C-class near-Earth asteroid 162173 (1999JU3) considered to contain organic or hydrated materials. The system consists of a TIR imager and digital electronics, which are used not only for the scientific investigation of physical properties of the asteroid surface, but also for the assessment of landing site selection and safe descent operation onto the asteroid surface with in situ measurement. TIR adopts an uncooled bolometer. Image operations such as multiple images summation, dark image subtraction, and the compensation of dead pixels are processed onboard. A processing module is connected to sensor interfaces through SpaceWire in order to provide deterministic processing time. Data compression is also provided to reduce the restriction of transmission time, which provides the equivalent compression ratio as JPEG2000 in 1/30 processing time in average. A high-speed data recorder is connected through SpaceWire in order to record TIR data in parallel with other sensor data. The modularity of SpaceWire enables us to use these as built devices for TIR and inherits the same design as the long-wavelength infrared imager developed for the Venus climate orbiter Akatsuki.

Hihara, Hiroki; Iwase, Kaori; Sano, Junpei; Otake, Hisashi; Okada, Tatsuaki; Funase, Ryu; Kashikawa, Ryoichi; Higashino, Isamu; Masuda, Tetsuya

2014-01-01

294

Research study on multi-KW DC distribution system  

NASA Technical Reports Server (NTRS)

Power distribution system noise and transient stress on switchgear in large space vehicle power systems were investigated in terms of the effect of flight designs of long power distribution cables on load interface EMI requirements. A fifty meter cable pair was simulated to study interactions between the cable, load, and power source terminations. Power system noise characteristics were evaluated based on current spacecraft data, interface hardware filter designs, and power cable parameters. Parametric approaches were defined for evaluating switching transients at various distribution voltage levels. It is concluded that the state-of-the-art semiconductor switches represent a viable approach toward the implementation of power system design with distribution voltages of 120 VDC or less. The interface definition and design for the bus control unit was updated to be consistent with the established requirements.

Berkery, E. A.

1975-01-01

295

Annular suspension and pointing system with controlled DC electromagnets  

NASA Technical Reports Server (NTRS)

The Annular Suspension and Pointing System (ASPS) developed by the Flight System division of Sperry Corporation is a six-degree of freedom payload pointing system designed for use with the space shuttle. This magnetic suspension and pointing system provides precise controlled pointing in six-degrees of freedom, isolation of payload-carrier disturbances, and end mount controlled pointing. Those are great advantages over the traditional mechanical joints for space applications. In this design, we first analyzed the assumed model of the single degree ASPS bearing actuator and obtained the plant dynamics equations. By linearizing the plant dynamics equations, we designed the cascade and feedback compensators such that a stable and satisfied result was obtained. The specified feedback compensator was computer simulated with the nonlinearized plant dynamics equations. The results indicated that an unstable output occurred. In other words, the designed feedback compensator failed. The failure of the design is due to the Taylor's series expansion not converging.

Vu, Josephine Lynn; Tam, Kwok Hung

1993-01-01

296

Analysis of Lightning Transients in a DC Traction Power System of Electrified Railway Using EMTP  

Microsoft Academic Search

This paper presented a modeling procedure for a DC traction power system (TPS) of electrified railway to study lightning transients with EMTP. The TPS included overhead lines, electric cables on the ground, masts and other associated components. The nonlinear ionization characteristic of earth resistance and the flashover characteristic of insulators were taken into account. These models were integrated to represent

Qi-Bin Zhou; Y. Du

2006-01-01

297

Optimal design of a D.C. railway power supply system  

Microsoft Academic Search

This paper presents the methodology to design a power supply system for a D.C. rail line or network in an optimal and efficient way. The input data for such purpose are the exact track profile of all routes or lines, the locomotives, freight cars and passenger coaches characteristics of all the vehicles to be used in each line, and the

D. Gonzalez; F. Manzanedo

2008-01-01

298

Starting algorithm and performance of a PM DC brushless motor drive system with no position sensor  

Microsoft Academic Search

The fundamentals of starting are investigated, and the development of an algorithm based on such an understanding is reported. The proposed algorithm is simulated, working with a full-wave inverter-controlled permanent-magnet DC brushless (PMDCBL) motor drive system. The simulation flowchart and results are described. Experimental results validating the starting algorithm are provided

R. Krishnan; R. Ghosh

1989-01-01

299

Detection of High-Impedance Arcing Faults in Radial Distribution DC Systems.  

National Technical Information Service (NTIS)

High voltage, low current arcing faults in DC power systems have been researched at the NASA Glenn Research Center in order to develop a method for detecting these 'hidden faults', in-situ, before damage to cables and components from localized heating can...

M. C. Gonzalez R. M. Button

2003-01-01

300

Hybrid trigeneration system management with a double DC-bus configuration on the electrical side  

Microsoft Academic Search

In this paper, a new control strategy is proposed to manage the electrical power of a hybrid trigeneration system composed of a concentrated photovoltaic and thermal captator, an electrical storage group (including lead acid batteries and supercapacitors), a genset and a lithium bromide absorption machine. The architecture is based on a double DC-bus configuration. An improved control management of the

L. Petrucci; Chiara Boccaletti; B. Francois; P. Di Felice

2009-01-01

301

Composite Superconducting Wires Obtained by High-Rate Tinning in Molten Bi-Pb-Sr-Ca-Cu-O System.  

National Technical Information Service (NTIS)

Long lengths of metal superconductor composites were prepared by passing a copper wire through the bismuth based molten oxide system at a constant speed. The key to successful composite preparation is the high pulling speed involved, which permits minimiz...

A. D. Grosav L. A. Konopko N. I. Leporda

1991-01-01

302

Flight experience with a fail-operational digital fly-by-wire control system  

NASA Technical Reports Server (NTRS)

The NASA Dryden Flight Research Center is flight testing a triply redundant digital fly-by-wire (DFBW) control system installed in an F-8 aircraft. The full-time, full-authority system performs three-axis flight control computations, including stability and command augmentation, autopilot functions, failure detection and isolation, and self-test functions. Advanced control law experiments include an active flap mode for ride smoothing and maneuver drag reduction. This paper discusses research being conducted on computer synchronization, fault detection, fault isolation, and recovery from transient faults. The F-8 DFBW system has demonstrated immunity from nuisance fault declarations while quickly identifying truly faulty components.

Brown, S. R.; Szalai, K. J.

1977-01-01

303

Design and test experience with a triply redundant digital fly-by-wire control system  

NASA Technical Reports Server (NTRS)

A triplex digital fly-by-wire flight control system was developed and then installed in a NASA F-8C aircraft to provide fail-operative, full authority control. Hardware and software redundancy management techniques were designed to detect and identify failures in the system. Control functions typical of those projected for future actively controlled vehicles were implemented. This paper describes the principal design features of the system, the implementation of computer, sensor, and actuator redundancy management, and the ground test results. An automated test program to verify sensor redundancy management software is also described.

Szalai, K. J.; Felleman, P. G.; Gera, J.; Glover, R. D.

1976-01-01

304

Design of Performance Driven Self-Tuning PID Control Systems and It's Application for DC-DC Converters  

NASA Astrophysics Data System (ADS)

This paper proposes an adaptive PID controller which is driven by current control performance. The calculations of the PID parameters are based on the generalized minimum variance control(GMVC) algorithm. The current control performance is obtained in an online manner over a user-specified time-window with some overlap. The retuning of PID parameters are only carried out when controller performance deteriorates below a user-specified threshold. Experimental evaluations on the voltage control of the DC-DC converter demonstrates the practicality and utility of this idea.

Ohnishi, Yoshihiro; Ikemoto, Takahiro; Yamamoto, Toru

305

The state-of-the-art of dc power distribution systems/components for space applications  

NASA Technical Reports Server (NTRS)

This report is a survey of the state of the art of high voltage dc systems and components. This information can be used for consideration of an alternative secondary distribution (120 Vdc) system for the Space Station. All HVdc components have been prototyped or developed for terrestrial, aircraft, and spacecraft applications, and are applicable for general space application with appropriate modification and qualification. HVdc systems offer a safe, reliable, low mass, high efficiency and low EMI alternative for Space Station secondary distribution.

Krauthamer, S.

1988-01-01

306

Wire Maze  

NSDL National Science Digital Library

Students gain a basic understanding of electrical circuits. They build wire circuits and pass paperclips through the mazes, trying not to touch the wires. Touching a wire with a paperclip causes the circuit to close, which activates an indicator.

K-12 Outreach Office,

307

The Separately Excited DC Traction Motor Applied to DC and Single-Phase AC Rapid Transit Systems and Electrified Railroads, Part I  

Microsoft Academic Search

The introduction of power thyristors and rectifiers in dc-dc chopper and ac-dc converter circuits allows the replacement of the traditional dc series motor by the separately excited dc motor. This paper will consider the characteristics and the application of separately excited dc motors operating from either a dc input with a dc chopper using dynamic braking, or from a single-phase

R. A. Van Eck

1971-01-01

308

Prospects of long-distance HTS DC power transmission systems  

NASA Astrophysics Data System (ADS)

Continual improvement of technologies for the safe use of power resources is a key to sustainable development of a human society. In particular, high-temperature superconductivity (HTS) should be used to meet the growing needs of the electric-power industry. It is known that HTS power cables allow us to increase the level of transmitted energy to several GW at voltage of 66-110 kV. HTS power cables of a coaxial design are almost ideal non-polluting system shielding electromagnetic field. In the present work we have tried to analyze various configurations of HTS power transmission systems, estimate the cable transmission capacitance depending on distance, and characterize reliability and efficiency of the systems.

Romashov, M. A.; Sytnikov, V. E.; Shakarian, Y. G.; Ivanov, Y. V.

2014-05-01

309

Negative impedance instability compensation in more electric aircraft DC power systems using state space pole placement control  

Microsoft Academic Search

In aerospace power systems, multiple power converters and multiple voltage power systems interact with each other and can result in unstable operation. When a dc-dc converter is loaded with a constant power load, it shows instability. This is because of the negative impedance characteristic of constant power load. Some poles of the converter with a constant power load are in

Seyoung Kim; Sheldon S. Williamson

2011-01-01

310

The basic investigation of the high-speed VCB and its application for the DC power system  

Microsoft Academic Search

The fundamental phenomena and applications of the high-speed vacuum circuit breakers, which forced the fault current to zero, in a DC power system for railways were investigated experimentally and through simulations. The results showed the necessary performance of high-speed VCBs for DC power systems. The test circuit breaker consisted of a vacuum interrupter, a high frequency current source and a

Y. Niwa; J. Matsuzaki; K. Yokokura

2008-01-01

311

Analysis of the DC side sudden short circuit of three-phase\\/twelve-phase synchronous generator system  

Microsoft Academic Search

As a compact, light, cheap, reliable and high quality power source, the hybrid AC\\/DC power supply generator (HADPSG) has been developing quickly in the mobile power systems. The most common fault in these systems is the short circuit in the DC load side. Research on the short circuit current peak amplitude and peak instant is carried out to provide safe

Li Yixiang; Wang Xiangheng; Wang Shanming; Su Pengsheng; Ma Weiming

2000-01-01

312

A new DC micro-grid system using renewable energy and electric vehicles for smart energy delivery  

Microsoft Academic Search

This paper proposes a new DC micro-grid system, which fully utilizes the renewable energy and electric vehicle for smart energy delivery. The proposed DC grid incorporates the AC supply module, standby energy module, renewable energy module, and storage energy module together, to execute the energy distribution. Hence, this grid system can offer a high quality power for the three types

Chunhua Liu; K. T. Chau; Chenxi Diao; J. Zhong; Xiaodong Zhang; Shuang Gao; Diyun Wu

2010-01-01

313

Design and Implementation of PID Controller in Programmable Logic Controller for DC Motor Position Control of the Conveyor System  

Microsoft Academic Search

Direct Current (DC) motor position control using Programmable Logic Controller (PLC) is one of the applications which are widely used in automation industries. The aim of this project is to implement a Proportional Integral Derivative (PID) controller in a DC motor control system of The Conveyor System. The project is consists of two stages, classical controller and PID controller. The

MUHAMMAD SHARFI NAJIB; MOHD SHAWAL JADIN; RAJA M. TAUFIKA; RAJA ISMAIL

314

Space vector modulation for a three-level NPC ac-dc converter system: An experimental investigation  

Microsoft Academic Search

Industrial and traction drives (used in automobile and electric locomotives) using induction motor, require a good control over torque and speed, reversible and regenerative speed control operation. Hence the drive topology requires both ac to dc conversion and dc to ac conversion system. In this paper, a three-level utility friendly the front-end neutral point clamped (NPC) converter system having four

Ranjan K. Behera; Shyama P. Das

2010-01-01

315

Current feedback in DC\\/DC converters by using toroidal transformers  

Microsoft Academic Search

A new current feedback method in DC\\/DC converters by using toroidal transformers is proposed. In most of the DC\\/DC converters the current provided to the load is composed of two components that run over different wires. In all these configurations, for instance buck, boost, Cuk, forward and push-pull converters, the proposed feedback method can be applied

M. Sanz; A. Llombart; J. Sallan

1996-01-01

316

Smoothly Adjustable dc Load  

NASA Technical Reports Server (NTRS)

Load circuit for testing dc power supplies adjusted without momentary interruptions typical of rheostat loads. Load current passes through power transistor and fixed resistor instead of wire-wound rheostat. In new circuit potentiometer used to adjust bias of power transistor and thereby adjust load. Components are standard, commercially available parts, mounted on transistor heat sink, forming compact package.

Patocka, C. G.

1986-01-01

317

Magnification of starting torques of dc motors by maximum power point trackers in photovoltaic systems  

NASA Technical Reports Server (NTRS)

Direct current (dc) motors are used in terrestrial photovoltaic (PV) systems such as in water-pumping systems for irrigation and water supply. Direct current motors may also be used for space applications. Simple and low weight systems including dc motors may be of special interest in space where the motors are directly coupled to the solar cell array (with no storage). The system will operate only during times when sufficient insolation is available. An important performance characteristic of electric motors is the starting to rated torque ratio. Different types of dc motors have different starting torque ratios. These ratios are dictated by the size of solar cell array, and the developed motor torque may not be sufficient to overcome the load starting torque. By including a maximum power point tracker (MPPT) in the PV system, the starting to rated torque ratio will increase, the amount of which depends on the motor type. The starting torque ratio is calculated for the permanent magnet, series and shunt excited dc motors when powered by solar cell arrays for two cases: with and without MPPT's. Defining a motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 was obtained for the permanent magnet motor and a magnification of 7 for both the series and shunt motors. The effect of the variation of solar insolation on the motor starting torque was covered. All motor types are less sensitive to insolation variation in systems including MPPT's as compared to systems with MPPT's. The analysis of this paper will assist the PV system designed to determine whether or not to include an MPPT in the system for a specific motor type.

Appelbaum, Joseph; Singer, S.

1989-01-01

318

Complex band structure eigenvalue method adapted to Floquet systems: topological superconducting wires as a case study.  

PubMed

For systems that can be modeled as a single-particle lattice extended along a privileged direction, such as, for example, quantum wires, the so-called eigenvalue method provides full information about the propagating and evanescent modes as a function of energy. This complex band structure method can be applied either to lattices consisting of an infinite succession of interconnected layers described by the same local Hamiltonian or to superlattices: systems in which the spatial periodicity involves more than one layer. Here, for time-dependent systems subject to a periodic driving, we present an adapted version of the superlattice scheme capable of obtaining the Floquet states and the Floquet quasienergy spectrum. Within this scheme the time periodicity is treated as existing along a spatial dimension added to the original system. The solutions at a single energy for the enlarged artificial system provide the solutions of the original Floquet problem. The method is suited for arbitrary periodic excitations, including strong and anharmonic drivings. We illustrate the capabilities of the methods for both time-independent and time-dependent systems by discussing: (a) topological superconductors in multimode quantum wires with spin-orbit interaction and (b) microwave driven quantum dots in contact with a topological superconductor. PMID:24353216

Reynoso, Andres A; Frustaglia, Diego

2014-01-22

319

Backaction Noise in Strongly Interacting Systems: The dc SQUID and the Interacting Quantum Point Contact  

NASA Astrophysics Data System (ADS)

We study the backaction noise and measurement the efficiency (i.e., noise temperature) of a dc SQUID amplifier and, equivalently, a quantum point-contact detector formed in a Luttinger liquid. Using a mapping to a dissipative tight-binding model, we show that these systems are able to reach the quantum limit even in regimes where several independent transport processes contribute to the current. We suggest how this is related to the underlying integrability of these systems.

Clerk, A. A.

2006-02-01

320

Uprated dc power system and thermal-hydraulic facilities at Columbia University. Final report  

Microsoft Academic Search

The necessity of carrying out large scale nuclear thermal-hydraulic simulations is increasing. Such experiments call for large power sources, and to meet those requirements the D.C. power system at the Heat Transfer Research Facility of Columbia University has been upgraded to 11.5 MW. The uprated system, its installations, various subsystems, and operations are described. The thermal-hydraulic loops and their auxiliary

W. E. Hovemeyer; S. R. Sreepada; J. E. Casterline

1978-01-01

321

Reversible AC Drive Systems Based on Parallel AC–AC DC-Link Converters  

Microsoft Academic Search

In this paper, two reversible single-phase-to-three-phase ac drive systems are proposed. They are composed of an induction motor fed by two parallel single-phase-to-three-phase dc-link converters without isolation transformers. Suitable modeling and control strategy of the systems based on odq approach, including the unbalanced case, are developed. The proposed topologies permit reducing the harmonic distortion and presents fault tolerance characteristics. Even

Cursino Brandão Jacobina; Euzeli Cipriano dos Santos; Nady Rocha; Bernard de S Gouveia; Edison Roberto Cabral da Silva

2010-01-01

322

Overcurrent Protection on Voltage-Source-Converter-Based Multiterminal DC Distribution Systems  

Microsoft Academic Search

This paper proposes a protection scheme which utilizes modern voltage-source converters as fast-acting current-limiting circuit breakers. This paper investigates the main challenges of detecting and localizing a fault, and interrupting it as quickly as possible in a multiterminal dc system. A system protection scheme consisting of smart relays associated with converters has been developed. The protection relays monitor local quantities

Mesut E. Baran; Nikhil R. Mahajan

2007-01-01

323

Advanced Medium-Voltage Bidirectional DC-DC Conversion Systems for Future Electric Energy Delivery and Management Systems  

Microsoft Academic Search

The distributed renewable energy generation and utilization are constantly growing, and are expected to be integrated with the conventional grid. The growing pressure for innovative solutions will demand power electronics to take an even larger role in future electric energy delivery and management systems, since power electronics are required for the conversion and control of electric energy by most dispersed

Haifeng Fan

2011-01-01

324

Development of a computer assistant programming system for micro\\/nano milling tool fabrication by multi-axis wire EDM  

Microsoft Academic Search

Micro\\/nano milling tools are usually made of ultra hard materials. Wire EDM (electrical discharge machining) may be the best choice to fabricate these tools conveniently and efficiently. For micro\\/nano milling tools with complicated three-dimensional (3D) geometries, manually programming method is not applicable. The CAM (computer-aided manufacturing) systems existing in the market don't take the special WEDM (Wire EDM) processes for

Xiang Cheng; Zhigang Wang; Shigeru Kobayashi; Kazuo Nakamoto; Kazuo Yamazaki

2009-01-01

325

Dc bias system of a 35 kV/90 MVA saturated iron core SFCL  

NASA Astrophysics Data System (ADS)

Saturated iron core superconducting fault current limiter (SIC-SFCL) is a promising fault current limiting device for high or extra-high voltage power grids. It has low impedance in normal power transmission and turns high impedance when a short-circuit takes place. The dc bias system of a saturated iron core superconducting fault current limiter plays a key role in realizing these features. Our 35 kV/90 MVA SIC-SFCL has been running live-grid since January 2008 at Puji substation in Yunnan, China. In this paper, the working principle of the dc bias system will be introduced and results of artificially imposed short-circuit tests will be provided, which verifies the validity of this system.

Sun, Yuwei; Gong, Weizhi; Wang, Jianzhong; Hong, Hui; Tian, Bo; Xin, Ying

2011-06-01

326

A high temperature superconductor dc SQUID planar gradiometer measurement system for routine inspections  

NASA Astrophysics Data System (ADS)

We have developed a high temperature superconductor (HTS) dc SQUID gradiometric measurement system for routine applications in non-destructive evaluations. Low values of the white flux noise and white field gradient noise were measured for gradiometers operating at 77 K. Low frequency noise was suppressed using an ac bias technique, even in a magnetically unshielded environment. First-order planar dc SQUID flip-chip gradiometers were used in the measurement system for stable operation under electromagnetically noisy conditions. A synchronous filter was employed to remove all harmonic components of parasitic line frequency interference. This improved the resolution of the system in a typical laboratory or industrial environment showing strong magnetic gradients of the line frequency signal due to nearby metallic constructions. Test scans of contaminations with magnetic particles were performed.

Faley, M. I.; Poppe, U.; Slobodchikov, V. Yu; Maslennikov, Yu V.; Urban, K.

2004-05-01

327

Preliminary system design study for a digital fly-by-wire flight control system for an F-8C aircraft  

NASA Technical Reports Server (NTRS)

The design of a fly-by-wire control system having a mission failure probability of less than one millionth failures per flight hour is examined. Emphasis was placed on developing actuator configurations that would improve the system performance, and consideration of the practical aspects of sensor/computer and computer/actuator interface implementation. Five basic configurations were defined as appropriate candidates for the F-8C research aircraft. Options on the basic configurations were included to cover variations in flight sensors, redundancy levels, data transmission techniques, processor input/output methods, and servo actuator arrangements. The study results can be applied to fly by wire systems for transport aircraft in general and the space shuttle.

Seacord, C. L.; Vaughn, D. K.

1976-01-01

328

Modeling, simulation and experimental validation of a generation system for Medium-Voltage DC Integrated Power Systems  

Microsoft Academic Search

In this paper, a demonstrative technological implementation of a shipboard 2.15 MVA generation system is described along with its modeling, numeric simulation and some factory tests. The system, named Naval Package (NP), is part of a demonstrative programme commissioned by Italian Navy for preliminary evaluations of Medium-Voltage DC (MVDC) supply technologies aimed at equipping her future vessels. The NP is

G. Sulligoi; A. Tessarolo; V. Benucci; M. Baret; A. Rebora; A. Taffone

2009-01-01

329

Desicription and flight test results of the NASA F-8 digital fly-by-wire control system  

NASA Technical Reports Server (NTRS)

A NASA program to develop digital fly-by-wire (DFBW) technology for aircraft applications is discussed. Phase I of the program demonstrated the feasibility of using a digital fly-by-wire system for aircraft control through developing and flight testing a single channel system, which used Apollo hardware, in an F-8C airplane. The objective of Phase II of the program is to establish a technology base for designing practical DFBW systems. It will involve developing and flight testing a triplex digital fly-by-wire system using state-of-the-art airborne computers, system hardware, software, and redundancy concepts. The papers included in this report describe the Phase I system and its development and present results from the flight program. Man-rated flight software and the effects of lightning on digital flight control systems are also discussed.

1975-01-01

330

Brushless DC motor control system responsive to control signals generated by a computer or the like  

NASA Technical Reports Server (NTRS)

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The motor is arranged so that each phase winding, when energized from a DC source, will drive the rotor through a predetermined angular position or step. A commutation signal generator responsive to the shaft position provides a commutation signal for each winding. A programmable control signal generator such as a computer or microprocessor produces individual digital control signals for each phase winding. The control signals and commutation signals associated with each winding are applied to an AND gate for that phase winding. Each gate controls a switch connected in series with the associated phase winding and the DC source so that each phase winding is energized only when the commutation signal and the control signal associated with that phase winding are present. The motor shaft may be advanced one step at a time to a desired position by applying a predetermined number of control signals in the proper sequence to the AND gates and the torque generated by the motor be regulated by applying a separate control signal and each AND gate which is pulse width modulated to control the total time that each switch connects its associated winding to the DC source during each commutation period.

Packard, D. T. (inventor)

1985-01-01

331

Brushless DC motor control system responsive to control signals generated by a computer or the like  

NASA Technical Reports Server (NTRS)

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The rotor is arranged so that each phase winding, when energized from a DC source, will drive the rotor through a predetermined angular position or step. A commutation signal generator responsive to the shaft position provides a commutation signal for each winding. A programmable control signal generator such as a computer or microprocessor produces individual digital control signals for each phase winding. The control signals and commutation signals associated with each winding are applied to an AND gate for that phase winding. Each gate controls a switch connected in series with the associated phase winding and the DC source so that each phase winding is energized only when the commutation signal and the control signal associated with that phase winding are present. The motor shaft may be advanced one step at a time to a desired position by applying a predetermined number of control signals in the proper sequence to the AND gates and the torque generated by the motor may be regulated by applying a separate control signal to each AND gate which is pulse width modulated to control the total time that each switch connects its associated winding to the DC source during each commutation period.

Packard, Douglas T. (Inventor); Schmitt, Donald E. (Inventor)

1987-01-01

332

Control System Design and Simulation of an AC\\/DC - DC\\/DC - DC\\/AC Power Converter for a Permanent Magnet Wind Power Generator in Rural Power Generation  

Microsoft Academic Search

This paper deals with the voltage and frequency control of the generated electricity from a permanent magnet wind-turbine. The wind turbine is directly connected to a permanent magnet synchronous generator in order to avoid the losses associated to the gearbox so that only an AC\\/DC\\/AC power converter is used to control the variable voltage and frequency. The AC\\/DC converter is

Roberto Morales; Rafael Ordonez; Marco A. Morales; Vicente Flores

2009-01-01

333

Hardware Model of a Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC).  

National Technical Information Service (NTIS)

A hardware model of a shipboard electrical distribution system based on aspects of the DDG 51 Flight IIA, Arleigh Burke class, 60Hz Alternating Current (AC) and the future direct current (DC) zonal electrical distribution system (ZEDS). These distribution...

C. N. Tidd

2010-01-01

334

Hardware Model Of A Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC).  

National Technical Information Service (NTIS)

A hardware model of a shipboard electrical distribution system based on aspects of the DDG 51 Flight IIA, Arleigh Burke class, 60Hz Alternating Current (AC) and the future direct current (DC), zonal electrical distribution system (ZEDS). These distributio...

C. N. Tidd

2010-01-01

335

Brushless DC (Direct Current) Motor Control System Responsive to Control Signals Generated by a Computer or the Like.  

National Technical Information Service (NTIS)

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The motor is arranged so that each phase winding, when energized from a DC source, wil...

D. T. Packard

1985-01-01

336

Texture development in Galfenol wire  

NASA Astrophysics Data System (ADS)

Galfenol (Fe-Ga alloy) wire fabrication provides a low cost alternative to directional solidification methods. This work evaluates the compositional dependence of the wire drawing suitability of Fe-Ga and characterizes the microstructural and magnetic properties of these wires. Wire has been produced with Ga contents between 10 at. % and 17 at. % to allow determination of the ductile to brittle transition (DTBT) in wire manufacture. Published results on chill cast bend specimens indicated that a DTBT occurs at roughly 15 at. % Ga. This DTBT was observed under tensile loading with a corresponding change in fracture behavior from transverse fracture to intergranular fracture. For improved magnetostrictive performance, higher Ga contents are desired, closer to the 17 at. % Ga evaluated in this work. Electron backscattered diffraction B-H loop and resonance measurements as a function of magnetic field (to determine modulus and coupling factor) are presented for as-drawn, furnace, and direct current (DC) annealed wire. Galfenol wire produced via traditional drawing methods is found to have a strong <110> (?) texture parallel to the drawing direction. As-drawn wire was observed to have a lower magnetic permeability and larger hysteresis than DC annealed wire. This is attributed to the presence of a large volume of crystalline defects; such as vacancies and dislocations.

Boesenberg, A. J.; Restorff, J. B.; Wun-Fogle, M.; Sailsbury, H.; Summers, E.

2013-05-01

337

DC-ATLAS: a systems biology resource to dissect receptor specific signal transduction in dendritic cells  

PubMed Central

Background The advent of Systems Biology has been accompanied by the blooming of pathway databases. Currently pathways are defined generically with respect to the organ or cell type where a reaction takes place. The cell type specificity of the reactions is the foundation of immunological research, and capturing this specificity is of paramount importance when using pathway-based analyses to decipher complex immunological datasets. Here, we present DC-ATLAS, a novel and versatile resource for the interpretation of high-throughput data generated perturbing the signaling network of dendritic cells (DCs). Results Pathways are annotated using a novel data model, the Biological Connection Markup Language (BCML), a SBGN-compliant data format developed to store the large amount of information collected. The application of DC-ATLAS to pathway-based analysis of the transcriptional program of DCs stimulated with agonists of the toll-like receptor family allows an integrated description of the flow of information from the cellular sensors to the functional outcome, capturing the temporal series of activation events by grouping sets of reactions that occur at different time points in well-defined functional modules. Conclusions The initiative significantly improves our understanding of DC biology and regulatory networks. Developing a systems biology approach for immune system holds the promise of translating knowledge on the immune system into more successful immunotherapy strategies.

2010-01-01

338

The Separately Excited DC Traction Motor Applied to DC and Single-Phase AC Rapid Transit Systems and Electrified Railroads, Part II---Application  

Microsoft Academic Search

The characteristics and the construction of the separately excited dc traction motor has been described in [1]. This type of motor can be used for traction only because of the availability of large power thyristors. In this paper, the type of control circuit required in order to use the separately excited dc motor (dc-dc chopper or ac-dc converters) will be

R. A. Van Eck

1971-01-01

339

Characteristic Analysis of DC Electric Railway Systems with Superconducting Power Cables Connecting Power Substations  

NASA Astrophysics Data System (ADS)

The application of superconducting power cables to DC electric railway systems has been studied. It could leads to an effective use of regenerative brake, improved energy efficiency, effective load sharing among the substations, etc. In this study, an electric circuit model of a DC feeding system is built and numerical simulation is carried out using MATLAB-Simulink software. A modified electric circuit model with an AC power grid connection taken into account is also created to simulate the influence of the grid connection. The analyses have proved that a certain amount of energy can be conserved by introducing superconducting cables, and that electric load distribution and concentration among the substations depend on the substation output voltage distribution.

Ohsaki, H.; Matsushita, N.; Koseki, T.; Tomita, M.

2014-05-01

340

Dc Superconducting Cables.  

National Technical Information Service (NTIS)

Progress in the development of dc superconducting cables suggests these systems will provide an attractive alternate among cable options where long lengths of high-capacity underground transmission lines are required. The general characteristics of dc sup...

W. E. Keller

1979-01-01

341

Radiation and impedance characteristics of a thin-wire transmission line-dipole system  

Microsoft Academic Search

Thin-wire transmission lines and dipoles, whose diameters are much less than the operating wavelength, carry currents which are essentially sinusoidal in form. Moreover, the electromagnetic field radiated by the filamentary (a??) straight wire of finite length can be specified exactly, even in the near zone of the wire. This made it possible for P.S. Carter (1932) to determine the input

Robert H. MacPhie

1989-01-01

342

Surface temperature profiles of the corona wire in a plate-wire type electrostatic precipitator  

Microsoft Academic Search

The corona wire surface temperature profiles in a plate-wire-type electrostatic precipitator have been measured by an IR thermal image technique and thermocouples under both DC positive and negative corona discharge conditions. The results show that: the corona wire surface temperature profiles under positive coronas are more uniform than those of the negative coronas, where the differences between maximum and minimum

T. OhkuboU; J. S. Chang; A. A. Berezin; Y. Nomoto; T. Adachi

1992-01-01

343

Backaction Noise in Strongly Interacting Systems: The dc SQUID and the Interacting Quantum Point Contact  

Microsoft Academic Search

We study the backaction noise and measurement the efficiency (i.e., noise temperature) of a dc SQUID amplifier and, equivalently, a quantum point-contact detector formed in a Luttinger liquid. Using a mapping to a dissipative tight-binding model, we show that these systems are able to reach the quantum limit even in regimes where several independent transport processes contribute to the current.

A. A. Clerk

2006-01-01

344

Fundamental investigation and application of high-speed VCB for DC power system of railway  

Microsoft Academic Search

The fundamental phenomena of the high-speed vacuum circuit breaker, which forced the fault current to zero, for the DC power system were investigated by the experiments. The interruption characteristics of the circuit breaker, which was consisted from a vacuum interrupter, a high frequency current source and a high-speed driving mechanism, were estimated experimentally. The arcing period of the high-speed vacuum

Y. Niwal; K. Yokokura; J. Matsuzaki

2010-01-01

345

Design and research on electrical\\/mechanical hybrid four-redundancy Brushless DC Motor system  

Microsoft Academic Search

Redundancy structure is widely adopted by motors in aircrafts and special vehicles with rigorous reliability requirements. This paper presents an electrical\\/mechanical hybrid four-redundancy brushless DC motor (BLDCM) and the corresponding driving control system. High reliability can be achieved by adopting the electrical\\/mechanical hybrid structure. An engineering prototype is designed and developed whereas the reliability of the BLDCM is analyzed theoretically.

Hong Guo; Wei Wang; Wei Xing; Yanming Li

2008-01-01

346

The Properties of Positive DC Corona Discharge in Iced Electrode System Under Low Atmospheric Pressure  

Microsoft Academic Search

Low air pressure and recurrent icing may affect the discharge characteristics of dielectrics and decrease the insulating performance of insulators. The aim of this paper is to investigate the corona discharge phenomena on ice-covered insulators at low air pressure based on an icicle\\/iced-plate electrode system with direct current (DC) positive voltage. Using a pulse current sensor and an ultraviolet camera,

SIMA Wen-xia; FENG Jie; YANG Qing; LAI Xiang-ping; D. Yu; M. Farzaneh; J. Zhang

2007-01-01

347

MIDAS, prototype Multivariate Interactive Digital Analysis System, phase 1. Volume 3: Wiring diagrams  

NASA Technical Reports Server (NTRS)

The Midas System is a third-generation, fast, multispectral recognition system able to keep pace with the large quantity and high rates of data acquisition from present and projected sensors. A principal objective of the MIDAS Program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turn-around time and significant gains in throughput. The hardware and software generated in Phase I of the overall program are described. The system contains a mini-computer to control the various high-speed processing elements in the data path and a classifier which implements an all-digital prototype multivariate-Gaussian maximum likelihood decision algorithm operating at 2 x 100,000 pixels/sec. Sufficient hardware was developed to perform signature extraction from computer-compatible tapes, compute classifier coefficients, control the classifier operation, and diagnose operation. The MIDAS construction and wiring diagrams are given.

Kriegler, F. J.; Christenson, D.; Gordon, M.; Kistler, R.; Lampert, S.; Marshall, R.; Mclaughlin, R.

1974-01-01

348

Digital Wires  

NASA Astrophysics Data System (ADS)

We study hardware implementations of cellular automata as reliable, adjustable, and secure commication lines. We discuss energy efficient digital wires on a nano-scale, all-optical digital wires, and digital wires as power lines and present performance data of a prototype digital wire, a six cells wide and ten cells long Boolean network. We show that digital wires have the following advantages: (i) Fixed pulse shape (pulses have a rectangular shape with a constant height and a constant width and produce no echos); (ii) Robust against electric smog. Digital wires based on semiconductor technology are effectively inert against electro-magnetic radiation, except for low-frequency radiation (heat) and high frequency radiation (X-rays). Digital wires based on plasma technology have in addition a very high tolerance for heat and X-rays. In digital wire the pulse speed can be rapidly adjusted. Signals on digital wires can be encrypted. Some digital wires can be used as general purpose computers. The data and the code are the input of the wire. Then both travel along the wire and `collide'. The collision is the computation. The result travels to the end of the wire, for further processing, as parallel input by a CPU, an actuator, or another digital wire.

Brown, Benny; Hubler, Alfred

2009-03-01

349

Stability of large DC power systems using switching converters, with application to the international space station  

NASA Technical Reports Server (NTRS)

As space direct current (dc) power systems continue to grow in size, switching power converters are playing an ever larger role in power conditioning and control. When designing a large dc system using power converters of this type, special attention must be placed on the electrical stability of the system and of the individual loads on the system. In the design of the electric power system (EPS) of the International Space Station (ISS), the National Aeronautics and Space Administration (NASA) and its contractor team led by Boeing Defense & Space Group has placed a great deal of emphasis on designing for system and load stability. To achieve this goal, the team has expended considerable effort deriving a dear concept on defining system stability in both a general sense and specifically with respect to the space station. The ISS power system presents numerous challenges with respect to system stability, such as high power, complex sources and undefined loads. To complicate these issues, source and load components have been designed in parallel by three major subcontractors (Boeing, Rocketdyne, and McDonnell Douglas) with interfaces to both sources and loads being designed in different countries (Russia, Japan, Canada, Europe, etc.). These issues, coupled with the program goal of limiting costs, have proven a significant challenge to the program. As a result, the program has derived an impedance specification approach for system stability. This approach is based on the significant relationship between source and load impedances and the effect of this relationship on system stability. This approach is limited in its applicability by the theoretical and practical limits on component designs as presented by each system segment. As a result, the overall approach to system stability implemented by the ISS program consists of specific hardware requirements coupled with extensive system analysis and hardware testing. Following this approach, the ISS program plans to begin construction of the world's largest orbiting power system in 1997.

Manners, B.; Gholdston, E. W.; Karimi, K.; Lee, F. C.; Rajagopalan, J.; Panov, Y.

1996-01-01

350

Development of Automotive Communication Based Real-Time Systems - A Steer-by-Wire Case Study  

NASA Astrophysics Data System (ADS)

Safety-critical automotive systems must fulfill hard real-time constraints to guarantee their reliability and safety requirements. In the context of network-based electronics systems, high-level timing requirements have to be carefully mastered and traced throughout the whole development process. In this paper, we outline the management of scheduling-specific timing information by the application of a steer-by-wire design example. We apply the principles of the AUTOSAR-compliant Timing Augmented Description Language (TADL) following the methodology introduced by the TIMMO project[2]. Focus of the example will be the identification of end-to-end timing constraints and their refinement by means of stimuli-response event chains.

Klobedanz, Kay; Kuznik, Christoph; Elfeky, Ahmed; Müller, Wolfgang

351

Magnification of starting torques of dc motors by maximum power point trackers in photovoltaic systems  

NASA Technical Reports Server (NTRS)

A calculation of the starting torque ratio of permanent magnet, series, and shunt-excited dc motors powered by solar cell arrays is presented for two cases, i.e., with and without a maximum-power-point tracker (MPPT). Defining motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 for the permanent magnet motor and a magnification of 7 for both the series and shunt motors are obtained. The study also shows that all motor types are less sensitive to solar insolation variation in systems including MPPTs as compared to systems without MPPTs.

Appelbaum, J.; Singer, S.

1989-01-01

352

Carrier frequency offset estimation for OFDM systems with time-varying DC Offset  

NASA Astrophysics Data System (ADS)

Orthogonal frequency division multiplexing (OFDM) systems with direct-conversion architecture suffer from both carrier frequency offset (CFO) and dc offset (DCO). In this paper, we study CFO estimation problem for OFDM systems with time-varying DCO (TV-DCO) caused by gain mode switch of low noise amplifier (LNA). Based on linear approximation of TV-DCO, a blind algorithm is proposed for CFO estimation by means of DCO compensation and power leakage minimization. Performance of the proposed algorithm is demonstrated by simulations.

Liu, Tao; Li, Hanzhang

2012-12-01

353

LANSCE-R WIRE-SCANNER ANALOG FRONT-END ELECTRONICS  

SciTech Connect

A new AFE is being developed for the new LANSCE-R wire-scanner systems. The new AFE is implemented in a National Instruments Compact RIO (cRIO) module installed a BiRa 4U BiRIO cRIO chassis specifically designed to accommodate the cRIO crate and all the wire-scanner interface, control and motor-drive electronics. A single AFE module provides interface to both X and Y wire sensors using true DC coupled transimpedance amplifiers providing collection of the wire charge signals, real-time wire integrity verification using the normal dataacquisition system, and wire bias of 0V to +/-50V. The AFE system is designed to accommodate comparatively long macropulses (>1ms) with high PRF (>120Hz) without the need to provide timing signals. The basic AFE bandwidth is flat from true DC to 50kHz with a true first-order pole at 50kHz. Numeric integration in the cRIO FPGA provides real-time pulse-to-pulse numeric integration of the AFE signal to compute the total charge collected in each macropulse. This method of charge collection eliminates the need to provide synchronization signals to the wire-scanner AFE while providing the capability to accurately record the charge from long macropulses at high PRF.

Gruchalla, Michael E. [Los Alamos National Laboratory

2011-01-01

354

Control Schemes for DC Capacitor Voltages Equalization in Diode-Clamped Multilevel Inverter-Based DSTATCOM  

Microsoft Academic Search

This paper examines the application of a diode-clamped multilevel inverter (DCMLI)-based distribution static compensator (DSTATCOM) connected to a three-phase, four-wire (3p4w) distribution system. The DCMLI has an inherent unbalancing problem among its DC capacitor voltages. Additionally, when the load contains a DC part, the neutral point of the compensator also becomes unbalanced. In this paper, the effects of different loading

Anshuman Shukla; Arindam Ghosh; Avinash Joshi

2008-01-01

355

A detailed RL fed bridge converter model for power flow studies in industrial AC\\/DC power systems  

Microsoft Academic Search

Because of lower voltage levels and smaller power ratings, the R\\/X ratio of commutation impedance in industrial AC\\/DC distribution systems is usually higher than that in HVDC transmission systems. Considerable discrepancies may therefore occur in industrial AC\\/DC power flow results, especially the reactive power consumption of converters, if the commutation resistances of the converters are neglected. To describe the effects

Yii-Shen Tzeng; Nanming Chen; Ruay-Nan Wu

1995-01-01

356

Wire Maze  

NSDL National Science Digital Library

Learners create an electrical-circuit maze out of wire, then try to pass a paperclip through the maze without touching the wire. If the paper clip touches the wire, it closes the circuit, causing a light to come on or a buzzer to sound. This activity requires a basic understanding of how to build an electrical circuit.

Institute, Worcester P.

2005-01-01

357

Galerkin-based modal analysis on the vibration of wire slurry system in wafer slicing using a wiresaw  

NASA Astrophysics Data System (ADS)

Wiresaws have been widely used in industries to slice semiconductor ingots into thin wafers for semiconductor fabrication. However, the surface roughness of a wiresaw-sliced wafer is usually not uniform which can be a concern in the subsequent lapping and polishing processes. It is sometimes observed that poor surface finish can occur at the beginning and the end of sliced round wafers when contact spans are short. In this paper, the dynamics of a coupled wire/slurry non-conservative vibration system is analyzed according to the rolling-indenting floating machining mechanism of typical wiresaw processes. Basic approaches adopted are the linearization of the coupled nonlinear governing equations with respect to the equilibrium, Galerkin-based discretization of the distributed non-conservative system, and the subsequent modal analysis. For the purpose of model verification, a numerical scheme of direct-time integration to an alternative finite element (FE) semi-discretized system is performed using the one-step Newmark's method. The results from the eigenanalysis of the Galerkin-based model are presented. These simulation results indicate that the wire/slurry system consists of both real and paired complex eigenvalues, which correspond to the over-damped modes and other vibration modes of the system. Parametric studies show that the vibration displacement of the wire decreases when the contact span expands, which explains the typical distribution of the surface roughness of a round wiresawn wafer. From the parametric studies, the tension and bow angle of the wire are found to play important roles in the response of the wire. Finally, in order to reduce the differential saw damage caused by the vibration of the wire, adaptive vibration control strategies are proposed for the wiresaw slicing processes.

Zhu, Liqun; Kao, Imin

2005-05-01

358

Resonance of metallic wire structures  

Microsoft Academic Search

Metallic wire structures form a common class of physical systems. We illustrate how to understand the general physics of the wire systems with a specific example, the split ring resonantor. We derived simple polynomial equations to determine the entire resonance spectra of split ring structures, which can be analytically solved in the limit of narrow wires. A resonance spectrum very

Lei Zhou; Y. Zhang; Siu Tat Chui

2008-01-01

359

Reliability analysis of the F-8 digital fly-by-wire system  

NASA Technical Reports Server (NTRS)

The F-8 Digital Fly-by-Wire (DFBW) flight test program intended to provide the technology for advanced control systems, giving aircraft enhanced performance and operational capability is addressed. A detailed analysis of the experimental system was performed to estimated the probabilities of two significant safety critical events: (1) loss of primary flight control function, causing reversion to the analog bypass system; and (2) loss of the aircraft due to failure of the electronic flight control system. The analysis covers appraisal of risks due to random equipment failure, generic faults in design of the system or its software, and induced failure due to external events. A unique diagrammatic technique was developed which details the combinatorial reliability equations for the entire system, promotes understanding of system failure characteristics, and identifies the most likely failure modes. The technique provides a systematic method of applying basic probability equations and is augmented by a computer program written in a modular fashion that duplicates the structure of these equations.

Brock, L. D.; Goodman, H. A.

1981-01-01

360

Mathematical model for the dc-ac inverter for the Space Shuttle  

NASA Astrophysics Data System (ADS)

The reader is informed of what was done for the mathematical modeling of the dc-ac inverter for the Space Shuttle. The mathematical modeling of the dc-ac inverter is an essential element in the modeling of the electrical power distribution system of the Space Shuttle. The electrical power distribution system which is present on the Space Shuttle is made up to 3 strings each having a fuel cell which provides dc to those systems which require dc, and the inverters which convert the dc to ac for those elements which require ac. The inverters are units which are 2 wire structures for the main dc inputs and 2 wire structures for the ac output. When 3 are connected together a 4 wire wye connection results on the ac side. The method of modeling is performed by using a Least Squares curve fitting method. A computer program is presented for implementation of the model along with graphs and tables to demonstrate the accuracy of the model.

Berry, Frederick C.

1987-11-01

361

Load converter interactions with the secondary system in the Space Station Freedom power management and distribution dc test bed  

NASA Technical Reports Server (NTRS)

The NASA LeRC in Cleveland, Ohio, is responsible for the design, development, and assembly of the Space Station Freedom (SSF) Electrical Power System (EPS). In order to identify and understand system level issues during the SSF program design and development phases, a system Power Management and Distribution (PMAD) dc test bed was assembled. Some of the objectives of this test bed facility are the evaluation of, system efficiency, power quality, system stability, and system protection and reconfiguration schemes. In order to provide a realistic operating scenario, dc Load Converter Units are used in the PMAD dc test bed to characterize the user interface with the power system. These units are dc to dc converters that provide the final system regulation before power is delivered to the load. This final regulation is required on the actual space station because the majority of user loads will require voltage levels different from the secondary bus voltage. This paper describes the testing of load converters in an end to end system environment (from solar array to loads) where their interactions and compatibility with other system components are considered. Some of the system effects of interest that are presented include load converters transient behavior interactions with protective current limiting switchgear, load converters ripple effects, and the effects of load converter constant power behavior with protective features such as foldback.

Lebron, Ramon C.

1992-01-01

362

Final Results of the Protected Superficial Femoral Artery Trial Using the FilterWire EZ System  

SciTech Connect

The purpose of this study was to evaluate the safety and efficacy of debris-capture for distal protection using the FilterWire EZ Embolic Protection System (Boston Scientific, Mountain View, CA) with the additional aim to further define the incidence of distal embolization during superficial femoral artery (SFA) interventions. A prospective, single-centre registry was designed to evaluate the performance of the FilterWire EZ in capturing debris during standard SFA percutaneous intervention. The PRO-RATA study included 30 patients suitable for PTA (Fontaine IIb to III or Rutherford I to II classification). The primary end points were occurrence of distal embolization or decreased runoff, improvement in ankle-brachial index ankle-brachial index (ABI) after the procedure, and number of filters containing emboli. Secondary end points included major adverse events (i.e., procedure- or device-related death and/or clinical target lesion revascularisation), device delivery, deployment success, and incidence of embolic recovery (patients with device success exhibiting embolic protection in the filter). Procedural success was determined as {<=}30% residual stenosis with no worsening of distal runoff as determined on angiography. A total of 29 patients (age 66.2 {+-} 12 years; total no. of limbs = 30; total no. of lesions = 30) suitable for PTA were enrolled in the study between February 2007 and March 2008. There were 26 patients with claudication (Fontaine IIB) and 3 patients with stage IV peripheral vascular disease. In one patient, lesions in both legs were treated. No procedural or device-related complications occured. The average degree of stenosis was 86 {+-} 7%. Stenosis length ranged from 8 to 88 mm. The average degree of residual stenosis was 10 {+-} 10%. ABI improved from 0.56 {+-} 0.16 to 0.92 {+-} 0.19 (P < 0.05). No restenosis or dissection was seen at 1-month ultrasound follow-up. Macroscopic debris was found in 27 of 30 filters of all distal protection devices used in all 29 patients. Debris particle size ranged from 90 to 2000 {mu}m (1200 {+-} 640). Histological debris analysis showed platelets, erythrocytes, inflammatory cells, extracellular matrix, and cholesterol as being the major components of emboli. Additional immunochemistry showed no correlation between lesion morphology and debris components. The FilterWire EZ is easy and safe to handle. The system caused no complications. In all cases, macroscopic debris was captured. Using a distal protection device during femoropopliteal interventions has the potential to prevent migration of debris, which may be important for high-risk patients with limited distal runoff.

Mueller-Huelsbeck, Stefan, E-mail: muehue@diako.d [Academic Teaching Hospitals Flensburg, Department of Diagnostic and Interventional Radiology/Neuroradiology (Germany); Huemme, Tim H.; Philipp Schaefer, J.; Charalambous, Nikolas [University Hospitals Schleswig-Holstein-Campus Kiel, Department of Radiology (Germany); Paulsen, Friedrich [University of Erlangen-Nuernberg, Department of Anatomy II (Germany); Heller, Martin; Jahnke, Thomas [University Hospitals Schleswig-Holstein-Campus Kiel, Department of Radiology (Germany)

2010-12-15

363

A high resolution wire scanner beam profile monitor with a microprocessor data acquisition system  

SciTech Connect

A beam profile monitor has been constructed for the NBS-LANL Racetrack Microtron. The monitor consists of two perpendicular 30 ..mu..m diameter carbon wires that are driven through an electron beam by a pneumatic actuator. A long-lifetime, electroformed nickel bellows is used for the linear-motion vacuum feedthrough. Secondary emission current from the wires and a signal from a transducer measuring the position of the wires are simultaneously digitized by a microprocessor to yield beam current density profiles in two dimensions. The wire scanner is designed for use with both pulsed and cw beams.

Cutler, R.I.; Mohr, D.L.; Whittaker, J.K.; Yoder, N.R.

1983-08-01

364

Cost Effective Open Geometry HTS MRI System amended to BSCCO 2212 Wire for High Field Magnets  

SciTech Connect

The original goal of this Phase II Superconductivity Partnership Initiative project was to build and operate a prototype Magnetic Resonance Imaging (MRI) system using high temperature superconductor (HTS) coils wound from continuously processed dip-coated BSCCO 2212 tape conductor. Using dip-coated tape, the plan was for MRI magnet coils to be wound to fit an established commercial open geometry, 0.2 Tesla permanent magnet system. New electronics and imaging software for a prototype higher field superconducting system would have added significantly to the cost. However, the use of the 0.2 T platform would allow the technical feasibility and the cost issues for HTS systems to be fully established. Also it would establish the energy efficiency and savings of HTS open MRI compared with resistive and permanent magnet systems. The commercial goal was an open geometry HTS MRI running at 0.5 T and 20 K. This low field open magnet was using resistive normal metal conductor and its heat loss was rather high around 15 kolwatts. It was expected that an HTS magnet would dissipate around 1 watt, significantly reduce power consumption. The SPI team assembled to achieve this goal was led by Oxford Instruments, Superconducting Technology (OST), who developed the method of producing commercial dip coated tape. Superconductive Components Inc. (SCI), a leading US supplier of HTS powders, supported the conductor optimization through powder optimization, scaling, and cost reduction. Oxford Magnet Technology (OMT), a joint venture between Oxford Instruments and Siemens and the world’s leading supplier of MRI magnet systems, was involved to design and build the HTS MRI magnet and cryogenics. Siemens Magnetic Resonance Division, a leading developer and supplier of complete MRI imaging systems, was expected to integrate the final system and perform imaging trials. The original MRI demonstration project was ended in July 2004 by mutual consent of Oxford Instruments and Siemens. Between the project start and that date a substantial shift in the MRI marketplace occurred, with rapid growth for systems at higher fields (1.5 T and above) and a consequent decline in the low field market (<1.0 T). While the project aim appeared technically attainable at that time, the conclusion was reached that the system and market economics do not warrant additional investment. The program was redirected to develop BSCCO 2212 multifilament wire development for high field superconducting magnets for NMR and other scientific research upon an agreement between DOE and Oxford Instruments, Superconducting Technology. The work t took place between September, 2004 and the project end in early 2006 was focused on 2212 multifilamentary wire. This report summarizes the technical achievements both in 2212 dip coated for an HTS MRI system and in BSCCO 2212 multifilamentary wire for high field magnets.

Kennth Marken

2006-08-11

365

Cooling of the 200 m superconducting DC power transmission system at Chubu University  

NASA Astrophysics Data System (ADS)

The fourth cooling test of the superconducting DC power transmission system of Chubu University was conducted in August of 2011. The heat leak from the cryogenic pipe and the eect of reducing the outer pipe temperature were tested. The heat leak from the cryogenic pipe was improved relative to that recorded during the second cooling test performedintheprevious summer,a season similartothatin whichthe fourth cooling testwas conducted.Asigni?cant reduction of the outer pipe temperature was achieved by an infrared re?ective coating, and a reduction of the heat leak was observed.

Watanabe, Hirofumi; Sun, Jian; Ivanov, Yury; Hamabe, Makoto; Kawahara, Toshio; Yamaguchi, Satarou

366

A COAXIAL TE011 CAVITY AND A SYSTEM TO MEASURE DC AND RF PROPERTIES OF SUPERCONDUCTORS  

SciTech Connect

A coaxial niobium cavity has been designed and built where the center conductor consists of a removable sample. In addition, a system to measure properties such as magnetization, penetration depth, critical temperature and thermal conductivity on the same cylindrical sample has been designed and built. The purpose of this effort is to investigate possible correlations between DC and RF properties of superconductors. In this contribution, the design of the various components is discussed and the test results on a niobium sample obtained so far are presented.

Gianluigi Ciovati; Peter Kneisel; Ganapati Myneni; Larry Turlington; Gary Slack; Michael Morrone; William Clemens; Richard Bundy; Thomas Elliott; Jayanta Mondal

2008-01-23

367

Earth to space dc to dc power transmission system utilizing a microwave beam as source of energy for electric propelled interorbital vehicles  

NASA Technical Reports Server (NTRS)

The paper contributes to the credibility of an electric propelled interorbital transportation system by introducing a new low-mass source of continuous dc power for electric propulsion and illustrating how the source can be economically tied to an electric utility on earth by an electronically steered microwave beam. The new thin-film rectenna, which functions as the receiving end of an earth-to-space microwave power transmission system is described. It is easily fabricated, is over 80 percent efficient, has a specific mass of no more than 2 kilograms per kilowatt of continuous dc power output, and is well adapted for deployment in space. The paper then describes a complete system consisting of the interorbital vehicle and the microwave power transmission system that supplies it with power. A design scenario is used to obtain performance data from the system in terms of vehicle transfer times, payload fractions, and costs. Electric energy costs are found to be less than $1000 per kilogram of payload delivered to geosynchronous orbit from low-earth orbit.

Brown, W. C.

1985-01-01

368

Power sequencing approach to fault isolation in dc systems: Influence of system parameters  

Microsoft Academic Search

We show that medium-voltage dc power buses can be protected against short circuit faults by coordinating the action of a converter that supplies power to the bus with the action of contactors that are used to reconfigure the bus connections. Following a fault, the bus is de-energized (so there is no large current to interrupt), one or more contactors are

Pietro Cairoli; Roger A. Dougal; Ugo Ghisla; Igor Kondratiev

2010-01-01

369

Solid State Remote Power Controllers for high voltage DC distribution systems  

NASA Technical Reports Server (NTRS)

Presently, hybrid Remote Power Controllers (RPC's) are in production and prototype units are available for systems utilizing 28VDC, 120VDC, 115VAC/400 Hz and 230VAC/400 Hz. This paper describes RPC development in a new area of application: HVDC distribution systems utilizing 270/300VDC. Two RPC current ratings, 1 amp and 2 amps, were selected for development as they are adequate to control 90% of projected system loads. The various aspects and trade-offs encountered in circuit development are discussed with special focus placed on the circuits that see the duress of the high dc potentials. The comprehensive evaluation tests are summarized which confirmed the RPC compliance with the specification and with system/load compatibility requirements. In addition, present technology status and new applications are summarized.

Billings, W. W.; Sundberg, G. R.

1977-01-01

370

Blind estimation of carrier frequency offset, I/Q imbalance and DC offset for OFDM systems  

NASA Astrophysics Data System (ADS)

Sensitivity to carrier frequency offset (CFO) is one of the biggest drawbacks of orthogonal frequency division multiplexing (OFDM) system. A lot of CFO estimation algorithms had been studied for compensation of CFO in OFDM system. However, with the adoption of direct-conversion architecture (DCA), which introduces additional impairments such as dc offset (DCO) and in-phase/quadrature (I/Q) imbalance in OFDM system, the established CFO estimation algorithms suffer from performance degradation. In our previous study, we developed a blind CFO, I/Q imbalance and DCO estimation algorithm for OFDM systems with DCA. In this article, we propose an alternative algorithm with reduced computation complexity and better accuracy. Performance of the proposed algorithm is demonstrated by simulations.

Liu, Tao; Li, Hanzhang

2012-12-01

371

An Analysis of Sub Sea Electric Power Transmission Techniques from DC to AC 50\\/60 Hz and Beyond  

Microsoft Academic Search

In the past decade, the significant improvements in high speed, high voltage transistor technology enabled the design of more sophisticated sub sea electrical power transmission systems. This is the case of the power-electronics-based single wire DC and high frequency AC transmission systems that appeared as alternatives to the traditional three phase transmission systems. Although such advanced alternatives have been employed

Michael C. Wrinch; M. A. Tomim; J. Marti

2007-01-01

372

Study of a guarded electrode system in the dc conductivity measurement of insulating liquid  

NASA Astrophysics Data System (ADS)

The design and choice of an electrode system is important in dc conductivity measurement of insulating liquid. In this paper, the electric field distribution of an electrode system which consists of two parallel circular metallic electrodes and a guard electrode has been studied using Comsol Multiphysics software. A new parameter, which is not yet involved in current standards, the edge radius, has been mentioned in the literature formerly and is currently discussed in a CIGRE working group. In this paper, the influence of this parameter has been investigated by means of field calculation. As seen from the simulating result, there are regions in the vicinity of the edges of the guard and measuring electrode that are under high electric field. If the edges of these two electrodes are sharp, the maximum electric field in the test cell will be much higher than the average field between the measuring electrode and the high voltage electrode. An empirical equation has been proposed to calculate this maximum field. The classic correction expression for an effective radius has been re-evaluated with the edge radius being taken into account. Experimental work has been performed to confirm this conclusion. Three kinds of mineral oils with different ageing times have been tested under the dc field using a guarded electrode system and the electric strengths of these oils have been estimated. A recommendation has been made to current standards in insulating liquid measurement.

Zhou, Yuan; Hao, Miao; Chen, George; Wilson, Gordon; Jarman, Paul

2014-07-01

373

Plant flavonoids target Pseudomonas syringae pv. tomato DC3000 flagella and type III secretion system.  

PubMed

Flavonoids are among the most abundant plant secondary metabolites involved in plant protection against pathogens, but micro-organisms have developed resistance mechanisms to those compounds. We previously demonstrated that the MexAB-OprM efflux pump mediates resistance of Pseudomonas syringae pv. tomato (Pto) DC3000 to flavonoids, facilitating its survival and the colonization of the host. Here, we have shown that tomato plants respond to Pto infection producing flavonoids and other phenolic compounds. The effects of flavonoids on key traits of this model plant-pathogen bacterium have also been investigated observing that they reduce Pto swimming and swarming because of the loss of flagella, and also inhibited the expression and assembly of a functional type III secretion system. Those effects were more severe in a mutant lacking the MexAB-OprM pump. Our results suggest that flavonoids inhibit the function of the GacS/GacA two-component system, causing a depletion of rsmY?RNA, therefore affecting the synthesis of two important virulence factors in Pto DC3000, flagella and the type III secretion system. These data provide new insights into the flavonoid role in the molecular dialog between host and pathogen. PMID:24249293

Vargas, Paola; Farias, Gabriela A; Nogales, Joaquina; Prada, Harold; Carvajal, Vivian; Barón, Matilde; Rivilla, Rafael; Martín, Marta; Olmedilla, Adela; Gallegos, María-Trinidad

2013-12-01

374

Modelling and analysis of multi-converter DC power electronic systems using the generalized state space averaging method  

Microsoft Academic Search

This paper presents a modular approach for the modelling and simulation of multi-converter DC power electronic systems based on the generalized state space averaging method. These systems may consist of many individual converters connected together to form large and complex systems. In addition to simplifying the analysis procedure, by using the proposed method, time step for analysis of the system

Ali Emadi

2001-01-01

375

Modeling and analysis of multiconverter DC power electronic systems using the generalized state-space averaging method  

Microsoft Academic Search

This paper presents a modular approach for the modeling and simulation of multiconverter DC power electronic systems based on the generalized state-space averaging method. These systems may consist of many individual converters connected together to form large and complex systems. In addition to simplifying the analysis procedure, by using the proposed method, the time step for analysis of the system

Ali Emadi

2004-01-01

376

Computer vision system for the measurement of IC wire-bond height  

Microsoft Academic Search

In the production of integrated circuits (ICs), the wire-bond operation constructs an electrical connection between the bond pads and the package leads using fine gold wire with diameter ranging from 25 ?m to 65 ?m. Good quality control of the bonding operation requires the bonded ball diameter and height on the aluminum pad of the silicon chip to be within

W. Zhang; L. M. Koh; Eddie M C Wong

1993-01-01

377

Prediction model for wire bonding process through adaptive neuro-fuzzy inference system  

Microsoft Academic Search

In the wire bonding process, different combinations of parameter values will directly affect wire bonding quality. The optimal combination of these parameter values is very important to ensure the overall process quality response. Therefore, it is necessary to investigate the effects and interactive relationship of the bonding parameters on the bonding quality. This paper chooses the response factors of shear

Jian Gao; Changhong Liu; Xin Chen; Detao Zheng; Ketian Li

2009-01-01

378

A First Look at Wired Sensor Networks for Video Surveillance Systems  

Microsoft Academic Search

High-bandwidth sensor applications such as video surveillance give rise to the need for a wired sensor network (WSN). We show IEEE 1394b FireWire to be a suitable candidate for a shared-medium WSN. We also propose a hybrid location-centric routing protocol for future WSNs with store and forward nodes.

Vijay Chandramohan; Kenneth J. Christensen

2002-01-01

379

Composite superconducting wires obtained by high-rate tinning in molten Bi-Pb-Sr-Ca-Cu-O system  

Microsoft Academic Search

Long lengths of metal superconductor composites were prepared by passing a copper wire through the bismuth based molten oxide system at a constant speed. The key to successful composite preparation is the high pulling speed involved, which permits minimization of the severe interaction between the unbuffered metal surface and the oxide melt. Depending on the temperature of the melt and

A. D. Grosav; L. A. Konopko; N. I. Leporda

1991-01-01

380

Three-phase four-wire Vienna I rectifier with active filter function including neutral current mitigation  

Microsoft Academic Search

In this paper a Vienna I rectifier is used to achieve active filtering function including the neutral wire current compensation (VR-AF) in a three-phase four-wire system. A linear quadratic with integral action regulator (LQIR) is designed to achieve overall DC bus voltage regulation, harmonics, reactive power and load's neutral current compensations. The converter model is set in the d-q-o rotating

Bachir Kedjar; Kamal AI-Haddad

2009-01-01

381

Assessment of Test Programs and Test Equipment Required for Proposed DC-Cable Test Facility.  

National Technical Information Service (NTIS)

Phelps Dodge Cable and Wire Company has been engaged in a US Department of Energy and New York State ERDA sponsored contract (DOE No. EX-76-C-01-2093) for the design and development of a +-600 kV dc cable system. As a special task related to this project,...

1981-01-01

382

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

SciTech Connect

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 the 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 includes 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.

Schwarze, G.E.

1994-09-01

383

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

NASA Technical Reports Server (NTRS)

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.

Schwarze, G. E.

1985-01-01

384

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

NASA Technical Reports Server (NTRS)

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 the 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.

Schwarze, G. E.

1985-01-01

385

DC conductivity and magnetic properties of piezoelectric-piezomagnetic composite system  

NASA Astrophysics Data System (ADS)

A series of composites (1-x) (Ni0.8Zn0.2Fe2O4)+x (BaTiO3), where x=0%, 20%, 40%, 60%, 80% and 100% BT content, have been prepared by the standard ceramic technique, then sintered at 1200 °C for 8 h. X-ray diffraction analysis shows that the prepared composites consist of two phases, ferrimagnetic and ferroelectric. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been studied at different temperatures. It was found that the DC electrical conductivity increases with increasing BT content. The values of the thermoelectric power were positive and negative for the composites indicating that there are two conduction mechanisms, hopping and band conduction, respectively. Using the values of DC electrical conductivity and thermoelectric power, the values of charge carrier mobility and the charge carrier concentration were calculated. Magnetic measurements (hysteresis loop and magnetic permeability) show that the magnetization decreases by increasing BT content. M-H loop of pure Ni0.6 Zn0.4 Fe2O4 composite indicates that it is paramagnetic at room temperature and that the magnetization is diluted by increasing the BT content in the composite system. The value of magnetoelectric coefficient for the composites decreases by increasing BT content for all the compositions except for 40% BT content, which may be due to the low resistivity of magnetic phase compared with the BT phase that causes a leakage of induced charges on the piezoelectric phase. Since both ferroelectric and magnetic phases preserve their basic properties in the bulk composite, the present BT-NZF composite are potential candidates for applications as pollution sensors and electromagnetic waves.

Hemeda, O. M.; Tawfik, A.; A-Al-Sharif; Amer, M. A.; Kamal, B. M.; El Refaay, D. E.; Bououdina, M.

2012-11-01

386

Investigations of some aspects of the spray process in a single wire arc plasma spray system using high speed camera  

NASA Astrophysics Data System (ADS)

A high speed camera has been used to record and analyze the evolution as well as particle behavior in a single wire arc plasma spray torch. Commercially available systems (spray watch, DPV 2000, etc.) focus onto a small area in the spray jet. They are not designed for tracking a single particle from the torch to the substrate. Using high speed camera, individual particles were tracked and their velocities were measured at various distances from the spray torch. Particle velocity information at different distances from the nozzle of the torch is very important to decide correct substrate position for the good quality of coating. The analysis of the images has revealed the details of the process of arc attachment to wire, melting of the wire, and detachment of the molten mass from the tip. Images of the wire and the arc have been recorded for different wire feed rates, gas flow rates, and torch powers, to determine compatible wire feed rates. High speed imaging of particle trajectories has been used for particle velocity determination using time of flight method. It was observed that the ripple in the power supply of the torch leads to large variation of instantaneous power fed to the torch. This affects the velocity of the spray particles generated at different times within one cycle of the ripple. It is shown that the velocity of a spray particle depends on the instantaneous torch power at the time of its generation. This correlation was established by experimental evidence in this paper. Once the particles leave the plasma jet, their forward speeds were found to be more or less invariant beyond 40 mm up to 500 mm from the nozzle exit.

Tiwari, N.; Sahasrabudhe, S. N.; Tak, A. K.; Barve, D. N.; Das, A. K.

2012-02-01

387

Easy route to superhydrophobic copper-based wire-guided droplet microfluidic systems.  

PubMed

Droplet-based microfluidic systems are an expansion of the lab on a chip concept toward flexible, reconfigurable setups based on the modification and analysis of individual droplets. Superhydrophobic surfaces are one suitable candidate for the realization of droplet-based microfluidic systems as the high mobility of aqueous liquids on such surfaces offers possibilities to use novel or more efficient approaches to droplet movement. Here, copper-based superhydrophobic surfaces were produced either by the etching of polycrystalline copper samples along the grain boundaries using etchants common in the microelectronics industry, by electrodeposition of copper films with subsequent nanowire decoration based on thermal oxidization, or by a combination of both. The surfaces could be easily hydrophobized with thiol-modified fluorocarbons, after which the produced surfaces showed a water contact angle as high as 171 degrees +/- 2 degrees . As copper was chosen as the base material, established patterning techniques adopted from printed circuit board fabrication could be used to fabricate macrostructures on the surfaces with the intention to confine the droplets and, thus, to reduce the system's sensitivity to tilting and vibrations. A simple droplet-based microfluidic chip with inlets, outlets, sample storage, and mixing areas was produced. Wire guidance, a relatively new actuation method applicable to aqueous liquids on superhydrophobic surfaces, was applied to move the droplets. PMID:19681579

Mumm, Florian; van Helvoort, Antonius T J; Sikorski, Pawel

2009-09-22

388

Towards a molecular QCA wire: simulation of write-in and read-out systems  

NASA Astrophysics Data System (ADS)

Among emerging beyond CMOS technologies Molecular Quantum Dot Cellular Automata (MQCA) are estimated as extremely promising for computational purposes. The elementary nanoelectronic devices are molecular systems in which the binary encoding is provided by the charge localization within a molecule. As a consequence, there is no current flowing among the cells and power dissipation is dramatically reduced. We study a new real molecule that was synthesized ad hoc for this technology. Differently with respect to previous contributions, this study has the aim of assessing the realistic properties of this molecule in a perspective experimental system based on a molecular wire principle. We use a combination of ab initio calculations and molecular dynamics simulations and analyze the molecule behavior when specific electric fields are applied to move the electrons inside the molecule in order to force a logic state. Our results allowed us (i) to asses the molecule behavior and to explore the working points of our experimental system for the write-in, (ii) to introduce in this scenario new metrics for studying and using these new devices from an electronic point of view, (iii) to give a perspective and to define design constraints for possible experimental solutions eligible for issue of molecule state read-out.

Pulimeno, A.; Graziano, M.; Demarchi, D.; Piccinini, G.

2012-11-01

389

Load converter interactions with the secondary system in the Space Station Freedom power management and distribution dc test bed  

Microsoft Academic Search

The NASA LeRC in Cleveland, Ohio, is responsible for the design, development, and assembly of the Space Station Freedom (SSF) Electrical Power System (EPS). In order to identify and understand system level issues during the SSF program design and development phases, a system Power Management and Distribution (PMAD) dc test bed was assembled. Some of the objectives of this test

Ramon C. Lebron

1992-01-01

390

An investigation of SiC-SIT DC circuit breakers for higher voltage direct current distribution systems  

Microsoft Academic Search

Recently, higher voltage direct current (HVDC) distribution systems are paid attention as highly efficient and reliable distribution systems. The over-current protection is one of the important issues in the realization of practical HVDC distribution systems. In this paper, as a solution to this problem, a semiconductor DC circuit breaker is investigated. A novel control method of the gate voltage waveform

Yukihiko Sato; Syunsuke Tobayashi; Yasunori Tanaka; Akiyoshi Fukui; Mikio Yamasaki; Hiromichi Ohashi

2010-01-01

391

Modeling and Analysis of DC Traction System in Light of Recent Innovations from HPC and Virtual Reality  

Microsoft Academic Search

We have developed a library for simulation of DC traction system. The modeling, installation and reliability aspects of Traction system in purview of current developments in HPC and Virtual reality are being implemented. We have proposed a model to predict and analyze traction system more comprehensively and put a computational structure regarding the same. Distribution of various computations is shown

Satyadhar Joshi; Rohit Pathak; Anil Jain

2009-01-01

392

An EEG (electroencephalogram) recording system with carbon wire electrodes for simultaneous EEG-fMRI (functional magnetic resonance imaging) recording  

PubMed Central

Simultaneous EEG-fMRI (Electroencephalography-functional Magnetic Resonance Imaging) recording provides a means for acquiring high temporal resolution electrophysiological data and high spatial resolution metabolic data of the brain in the same experimental runs. Carbon wire electrodes (not metallic EEG electrodes with carbon wire leads) are suitable for simultaneous EEG-fMRI recording, because they cause less RF (radio-frequency) heating and susceptibility artifacts than metallic electrodes. These characteristics are especially desirable for recording the EEG in high field MRI scanners. Carbon wire electrodes are also comfortable to wear during long recording sessions. However, carbon electrodes have high electrode-electrolyte potentials compared to widely used Ag/AgCl (silver/silver-chloride) electrodes, which may cause slow voltage drifts. This paper introduces a prototype EEG recording system with carbon wire electrodes and a circuit that suppresses the slow voltage drift. The system was tested for the voltage drift, RF heating, susceptibility artifact, and impedance, and was also evaluated in a simultaneous ERP (event-related potential)-fMRI experiment.

Negishi, Michiro; Abildgaard, Mark; Laufer, Ilan; Nixon, Terry; Constable, Robert Todd

2008-01-01

393

Next Generation Wiring  

NASA Technical Reports Server (NTRS)

Wiring is a major operational component on aerospace hardware that accounts for substantial weight and volumetric space. Over time wire insulation can age and fail, often leading to catastrophic events such as system failure or fire. The next generation of wiring must be reliable and sustainable over long periods of time. These features will be achieved by the development of a wire insulation capable of autonomous self-healing that mitigates failure before it reaches a catastrophic level. In order to develop a self-healing insulation material, three steps must occur. First, methods of bonding similar materials must be developed that are capable of being initiated autonomously. This process will lead to the development of a manual repair system for polyimide wire insulation. Second, ways to initiate these bonding methods that lead to materials that are similar to the primary insulation must be developed. Finally, steps one and two must be integrated to produce a material that has no residues from the process that degrades the insulating properties of the final repaired insulation. The self-healing technology, teamed with the ability to identify and locate damage, will greatly improve reliability and safety of electrical wiring of critical systems. This paper will address these topics, discuss the results of preliminary testing, and remaining development issues related to self-healing wire insulation.

Medelius, Petro; Jolley, Scott; Fitzpatrick, Lilliana; Vinje, Rubiela; Williams, Martha; Clayton, LaNetra; Roberson, Luke; Smith, Trent; Santiago-Maldonado, Edgardo

2007-01-01

394

Study of Wire Rope Systems for Seismic Protection of Equipment in Buildings.  

National Technical Information Service (NTIS)

Wire rope isolators have found numerous applications in the shock and vibration isolation of military hardware and industrial machinery. In the study, the usefulness of these devices for the seismic protection of equipment in buildings is investigated. In...

A. M. Reinhorn G. F. Demetriades M. C. Constantinou

1992-01-01

395

Research on an X-ray non-destructive testing system for conveyer belt with steel wire ropes  

Microsoft Academic Search

The thesis conducts a deep research on an X-ray non-destructive testing system for the conveyer belt with steel wire ropes, and proposes the detailed design program. By researching the image processing algorithm of the conveyer belt, the research realized the marginal check, joint elongation check and breakdown location. Meanwhile, a system software was developed by using the C#.NET programming design

Ye Chunqing; Miao Changyun

2010-01-01

396

An Intelligent Warehouse Stock Management and Tracking System Based on Silicon Identification Technology and 1Wire Network Communication  

Microsoft Academic Search

This paper presents a novel electronic system for stock control and container tracking in a storage warehouse environment. The system is based on the use of advanced electronic identification tags and 1-Wire communication tools. Each warehouse container is affixed with a small electronic ID tag (called iButton). The tag is an electronic chip housed in a durable 16mm button-shaped stainless

Kai-Xin Tee; Moi-Tin Chew; Serge Demidenko

2011-01-01

397

Characteristics of silicon nano wire as piezoresistor for nano electro mechanical systems  

Microsoft Academic Search

In order to confirm ability of silicon nano wire piezoresistors as sensing element of mechanical sensors, current-voltage (I-V) characteristics and the piezoresistive effect were investigated. Electron beam (EB) direct writing and RIE were used for fabrication. Fabricated polycrystalline Si (poly-Si) nano wire piezoresistors have triangular or trapezoid cross sections. The minimum width is 53 nm and thickness is 32 nm.

Toshiyuki Toriyama; Yasutada Tanimoto; Susumu Sugiyama

2001-01-01

398

An Analytical Design Method for a Regenerative Braking Control System for DC-electrified Railway Systems under Light Load Conditions  

NASA Astrophysics Data System (ADS)

A DC-electrified railway system that is fed by diode rectifiers at a substation is unable to return the electric power to an AC grid. Accordingly, the braking cars have to restrict regenerative braking power when the power consumption of the powering cars is not sufficient. However, the characteristics of a DC-electrified railway system, including the powering cars, is not known, and a mathematical model for designing a controller has not been established yet. Hence, the object of this study is to obtain the mathematical model for an analytical design method of the regenerative braking control system. In the first part of this paper, the static characteristics of this system are presented to show the position of the equilibrium point. The linearization of this system at the equilibrium point is then performed to describe the dynamic characteristics of the system. An analytical design method is then proposed on the basis of these characteristics. The proposed design method is verified by experimental tests with a 1kW class miniature model, and numerical simulations.

Saito, Tatsuhito; Kondo, Keiichiro; Koseki, Takafumi

399

Residential Wiring.  

ERIC Educational Resources Information Center

The second in a series of three curriculum packages on wiring, these materials for a five-unit course were developed to prepare postsecondary students for entry-level employment in the residential wiring trade. The five units are: (1) blueprint reading and load calculations; (2) rough-in; (3) service; (4) trim out and troubleshooting; and (5) load…

Taylor, Mark

400

A study on DC hybrid three-phase fault current limiting interrupter for a power distribution system  

NASA Astrophysics Data System (ADS)

For the purpose of protecting electric power system, many researches and developments of fault current limiters are being performed. The authors studied a dc hybrid three-phase fault current limiting interrupter (FCLI) composed of a superconducting reactor and an S/N transition element, connected in series each other. The dc hybrid type fault current limiting interrupter can limit a fault current by means of the inductance of high temperature superconducting (HTS) coil together with the normal transition of HTS bulk material (HTSB). In the case of an accident, the normal transition of the bulk material can be accelerated by the magnetic field of the HTS coil. In this paper, the dc hybrid type fault current limiting interrupter for 5.5 km long 6.6 kV-600 A power distribution system is analyzed, and performances of fault current limitation and interruption are confirmed. Moreover, a reclosing operation is discussed for this power distribution system.

Shao, Hongtian; Satoh, Tomoyuki; Yamaguchi, Mitsugi; Fukui, Satoshi; Ogawa, Jun; Satoh, Takao; Ishikawa, Hiroyuki

2005-10-01

401

A Novel Integrated Magnetic Structure Based DC/DC Converter for Hybrid Battery/Ultracapacitor Energy Storage Systems  

SciTech Connect

This manuscript focuses on a novel actively controlled hybrid magnetic battery/ultracapacitor based energy storage system (ESS) for vehicular propulsion systems. A stand-alone battery system might not be sufficient to satisfy peak power demand and transient load variations in hybrid and plug-in hybrid electric vehicles (HEV, PHEV). Active battery/ultracapacitor hybrid ESS provides a better solution in terms of efficient power management and control flexibility. Moreover, the voltage of the battery pack can be selected to be different than that of the ultracapacitor, which will result in flexibility of design as well as cost and size reduction of the battery pack. In addition, the ultracapacitor bank can supply or recapture a large burst of power and it can be used with high C-rates. Hence, the battery is not subjected to supply peak and sharp power variations, and the stress on the battery will be reduced and the battery lifetime would be increased. Utilizing ultracapacitor results in effective capturing of the braking energy, especially in sudden braking conditions.

Onar, Omer C [ORNL

2012-01-01

402

Superconducting fault current limiter to mitigate the effect of DC line fault in VSC-HVDC system  

Microsoft Academic Search

Voltage source converter based HVDC systems involving overhead transmission lines are prone to severe over-voltages during line faults. At present, they find applications only in back to back and\\/or underground cable transmission, with low power ratings. A conventional HVDC system suppresses the dc fault very well with the controllers and smoothing reactors while the same is not true with voltage

Premila Manohar; Wajid Ahmed

2012-01-01

403

Primary phase alignment in the Mg-Sb system with a 35T DC magnetic field  

NASA Astrophysics Data System (ADS)

Primary phase alignment behavior in the Mg-Sb system is explored by solidification of samples in a 35 tesla DC magnetic field. Compositions with multiple solidification reaction pathways are found to have different phase alignment characteristics. In the current study, the orientation of Mg and Sb primary grains do not appear to be strongly influenced, but the ?-Mg3Sb2 shows a very strong tendency to align with its long axis perpendicular to the field direction. In comparing two compositions that both first nucleate ?-Mg3Sb2 from the melt, it is found that the volume fraction involved in the primary reaction is a controlling factor for the total degree of alignment throughout the structure. This volume fraction dependence is interpreted as hindering free rotation in the liquid.

Imhoff, Seth; Ott, Thomas; Tucker, Tim; Cooley, Jason

2013-03-01

404

DC electrostatic gyro suspension system for the Gravity Probe B experiment  

NASA Astrophysics Data System (ADS)

The Gravity Probe B experiment is a satellite-based experiment primarily designed to test two aspects of Einstein's General Theory of Relativity by observing the spin axis drift of near-perfect gyroscopes in a 650-km circular polar orbit. The goal of this experiment is to measure the drift angles to an accuracy of 0.3 milli-arcsec after one year in orbit. As a result, electrostatically suspended free-spinning gyroscopes operating at a very low temperature became the final choice for their ultra-low Newtonian torque-induced drift rate. The Conventional AC current-driven suspension system faces two fundamental difficulties for ground gyro testing. Field emission causes rotor charging and arcing with an imperfect electrode or rotor surfaces because the electric field intensity needed to support a solid rotor in the 1-g field is more than 107 V/m. The system not only becomes unstable at a high rotor charge, which can be more than 500 volts, but may also lose control in case of arcing. Both the high voltage AC suspension signal and the high frequency (1 MHz) signal for rotor position sensing interfere with the superconducting SQUID magnetometer for spin axis readout through inductive coupling. These problems were resolved by using DC voltage to generate a suspension force and a low frequency position sensor. In addition to the Input/Output linearization algorithm developed to remove the system nonlinearity for global stability and dynamic performance, we also minimized the electric field intensity to reduce rotor charging. Experimental results verified the desired global stability and satisfactory dynamic performance. The problem of rotor charging is virtually eliminated. More importantly, the DC system is compatible with the SQUID readout system in the Science Mission configuration. Consequently, experiments in low magnetic field at a sub-micro-gauss level for SQUID design verification and trapped flux distribution study were finally realizable in ground environment. The second part of the research focused on design issues for the Science Mission in a micro-g environment. The unique requirement of the GP-B experiment is to minimize suspension-induced torque and subsequent spin axis drift. A nonlinear control law which employs stiffened spring and stiffened damping coefficients was developed to achieve both low RMS noise in steady-state operation and quick response for situations like a micrometeoroid impact. Rotor voltage measurement and in-flight sensor bias correction schemes were developed to ensure system stability and absolute centering accuracy. Simulation results verified the system performances and confirmed that a suspension system induced rotor spin axis drift lower than 0.1 milli arcsec/year can be reached.

Wu, Chang-Huei

1994-12-01

405

Development of the electronic control unit for the rack-actuating steer-by-wire using the hardware-in-the-loop simulation system  

Microsoft Academic Search

The steer-by-wire (SBW) system in a passenger car substitutes the typical mechanical linkage between the steering wheel and the front wheel with electric wires. The control conception of the rack-actuating SBW system was proposed in this paper. Basically, the controller should compensate for a conventional steering system composed of mechanical linkages. The hardware-in-the-loop-simulation (HILS) system was developed for the electronic

Tong-Jin Park; Chang-Soo Han; Sang-Ho Lee

2005-01-01

406

Ionization fronts in planar dc discharge systems with high-ohmic electrode.  

PubMed

Electric breakdown and ionization fronts are considered theoretically in a sandwich-like dc discharge system consisting of two plane-parallel electrodes and a gaseous gap in between. The key system feature is a high-ohmic cathode opposite to an ordinary metal anode. Such systems have received much attention from experimental studies because they naturally support current patterns. Using adiabatic description of electrons and two-scale expansion we demonstrate that in the low-current Townsend mode the discharge is governed by a two-component reaction-diffusion system. The latter provides quantitative system description on the macroscopic time scale (i.e., much larger than the ion travel time). The breakdown appears as an instability of the uniform overvoltage state. A seed current fluctuation triggers a shock-like ionization front that propagates along the discharge plane with constant speed (typically approximately 10(4) cm/s). Depending on the cathode resistivity the front exhibits either monotonic or oscillatory behavior in space. Other breakdown features, such as damping transient oscillations of the global current, can also be found as solutions of the reaction-diffusion equations. PMID:16089877

Amiranashvili, Sh; Gurevich, S V; Purwins, H-G

2005-06-01

407

Working with Systems and Thinking Systemically--Disentangling the Crossed Wires  

ERIC Educational Resources Information Center

This article explores two separate traditions that educational psychologists (EPs) in the UK have for working with systems. One of these is "systems work" with organisations such as schools. The other is "systemic thinking" for working with families. Over the years these two traditions, systems work and systemic thinking, have become crossed and…

Fox, Mark

2009-01-01

408

Partial Discharge Detection of Continuous Length Wire  

Microsoft Academic Search

The ability to eliminate or minimize defects in high voltage wire can help in extending system reliability by eliminating or minimizing sources of partial discharge. Partial discharge testing of single conductor wire is traditionally performed on discrete lengths of wire or wires terminated to connectors. However, when excessive partial discharge is detected in completed assemblies, expensive rework is the result.

J. L. Rush

2006-01-01

409

Analyzing the optimal matching of dc motors to photovoltaic modules via dc-dc converters  

Microsoft Academic Search

Because to the nonlinear behavior of the photovoltaic (PV) cells, dc-dc power converters are added for matching the load to the photovoltaic modules (PVM). In this paper, we use mathematical models in order to examine the behavior of the off-grid photovoltaic system composed by: PV generator, dc-dc converter and dc motor. We compare different converter topologies (step-up, step-down and step-down\\/step-up)

Jesus Gonzalez-Llorente; Eduardo I. Ortiz-Rivera; Andres Salazar-Llinas; Emil Jimenez-Brea

2010-01-01

410

New fault location system for power transmission lines using composite fiber-optic overhead ground wire (OPGW)  

SciTech Connect

A new fault location (FL) method using composite fiber-optic overhead ground wires (OPGWs) is developed to find out where electrical faults occur on overhead power transmission lines. This method locates the fault section by detecting the current induced in the ground wire (GW), i.e. OPGW in this system. Since detected fault information is essentially uncertain, the new FL method treats the fault information oas a current distribution pattern throughout the power line, and applies Fuzzy Theory to realize the human-like manner of fault location used by electrical power engineers. It was confirmed by computer simulations that the fault section can be accurately located using this method under various conditions. This FL system has already been applied to several commercial power transmission lines and successfully located the sections where electrical faults occurred on actual power transmission lines.

Urasawa, K. (Tokyo Electric Power Co., Inc. (Japan)); Kanemaru, K.; Toyota, S.; Sugiyama, K. (Hitachi Cable, Ltd., Tokyo (Japan))

1989-10-01

411

Accuracy of Fault Current DC Component Calculation in Multi-machine Power System  

NASA Astrophysics Data System (ADS)

Accuracy of the calculation method of transient DC component of three phase short circuit current is carefully studied. Using a multi-machine model system 4 different methods are compared, which are catenacci method, AIEE method, 4 parameters method, and the proposed method. Among all these four methods the proposed method gives the most accurate result, which gives almost identical wave form of the averaged wave obtained by the post processing of ATP-EMTP results. Compared to ATP-EMTP the proposed method is more convenient because it automatically gives the severest fault case while ATP-EMTP needs several computations. Main reason of the discrepancies of the conventional methods is based on the insufficient order of the internal models. In contrast to the proposed method, they use only a second order model at most. The usefulness of the proposed method is demonstrated using a test analysis of the saturation of a current transformer. Computing time is also discussed by comparing the results applied to two 10-machines systems and one 30-machines system. In conclusion, the proposed method is accurate and is ready to apply to multi-machine systems within a realistic computing time. The usefulness of the proposed method is confirmed by this study.

Kumano, Teruhisa

412

Lowest of AC-DC power output for electrostrictive polymers energy harvesting systems  

NASA Astrophysics Data System (ADS)

Advances in technology led to the development of electronic circuits and sensors with extremely low electricity consumption. At the same time, structural health monitoring, technology and intelligent integrated systems created a need for wireless sensors in hard to reach places in aerospace vehicles and large civil engineering structures. Powering sensors with energy harvesters eliminates the need to replace batteries on a regular basis. Scientists have been forced to search for new power source that are able to harvested energy from their surrounding environment (sunlight, temperature gradients etc.). Electrostrictive polymer belonging to the family of electro-active polymers, offer unique properties for the electromechanical transducer technology has been of particular interest over the last few years in order to replace conventional techniques such as those based on piezoelectric or electromagnetic, these materials are highly attractive for their low-density, with large strain capability that can be as high as two orders of magnitude greater than the striction-limited, rigid and fragile electroactive ceramics. Electrostrictive polymers sensors respond to vibration with an ac output signal, one of the most important objectives of the electronic interface is to realize the required AC-DC conversion. The goal of this paper is to design an active, high efficiency power doubler converter for electrostrictive polymers exclusively uses a fraction of the harvested energy to supply its active devices. The simulation results show that it is possible to obtain a maximum efficiency of the AC-DC converter equal to 80%. Premiliminary experimental measurements were performed and the results obtained are in good agreement with simulations.

Meddad, Mounir; Eddiai, Adil; Hajjaji, Abdelowahed; Guyomar, Daniel; Belkhiat, Saad; Boughaleb, Yahia; Chérif, Aida

2013-11-01

413

DC Voltage Control of the DC Micro-Grid for Super High Quality Electric Power Distribution  

Microsoft Academic Search

``DC Micro-grid'' is a novel power system using dc distribution in order to provide super high quality electric power. The power is distributed through dc distribution line and converted to required ac or dc voltages by converters placed near loads. The load side converters do not need transformers by choosing proper distributed dc voltage (±170V). The dc distribution line is

Hiroaki Kakigano; Yushi Miura; Toshifumi Ise; Ryohei Uchida

2007-01-01

414

A Negative Sequence Compensation Method Based on a Two-Phase Three-Wire Converter for a High-Speed Railway Traction Power Supply System  

Microsoft Academic Search

This paper presents a negative sequence compensation system based on a novel two-phase three-wire converter to eliminate a negative sequence current for the high-speed railway traction power system with a three-phase V\\/V traction transformer. In this compensation system, the proposed two-phase three-wire converter is fed by two single-phase power sources formed with two step-down transformers connecting to the two feeder

Chuanping Wu; An Luo; John Shen; Fu Jun Ma; Shuangjian Peng

2012-01-01

415

Simulation of current filamentation in a dc-driven planar gas discharge-semiconductor system  

NASA Astrophysics Data System (ADS)

We have performed a theoretical study of self-organized current filamentation in a dc-driven planar gas discharge-semiconductor system at very low currents and under cryogenic conditions. The discharge instability and the observed formation of current filaments are explained by a thermal mechanism, as proposed in our previous paper. We have found, for the first time, a stationary periodic current structure in a two-dimensional Cartesian geometry from first principles, by numerically solving the general system of continuity equations for ions and electrons, the Poisson equation for the electric field in the gas, together with the equation for gas temperature and the equation for electric field in the semiconductor. The space charge induced electric field redistribution, which usually leads to a discharge instability and is automatically included in the first three equations of the system, is practically absent at the very low currents considered, and thus it cannot be responsible for the discharge instability. This is why another mechanism of filamentation (thermal) should be considered. The calculated periodic current structure agrees with the hexagonal current pattern observed in the experiment, as well as with the periodic current structure found in the frame of the previously developed simple model. This serves as a corroboration of the fact that the thermal effect is essential for pattern formation under the conditions considered.

Mokrov, M. S.; Raizer, Yu P.

2011-10-01

416

DC CIRCUIT POWERED BY ORBITAL MOTION: MAGNETIC INTERACTIONS IN COMPACT OBJECT BINARIES AND EXOPLANETARY SYSTEMS  

SciTech Connect

The unipolar induction DC circuit model, originally developed by Goldreich and Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction torque and energy dissipation rate in such a model. This arises because when the resistance of the circuit is too small, the large current flow severely twists the magnetic flux tube connecting the two binary components, leading to the breakdown of the circuit. Applying this limit, we find that in coalescing neutron star binaries, magnetic interactions produce negligible correction to the phase evolution of the gravitational waveform, even for magnetar-like field strengths. However, energy dissipation in the binary magnetosphere may still give rise to electromagnetic radiation prior to the final merger. For ultracompact white dwarf binaries, we find that unipolar induction does not provide adequate energy dissipation to explain the observed X-ray luminosities of several sources. For exoplanetary systems containing close-in Jupiters or super-Earths, the magnetic torque and energy dissipation induced by the orbital motion are negligible, except possibly during the early T Tauri phase, when the stellar magnetic field is stronger than 10{sup 3} G.

Lai Dong [Department of Astronomy, Cornell University, Ithaca, NY 14850 (United States)

2012-09-20

417

A novel system for studies of dc discharge in cylindrical magnetron  

NASA Astrophysics Data System (ADS)

In a cylindrical magnetron, the electric field is applied in the radial direction and the magnetic field in the axial direction. In this paper, we present a description of a novel construction of cylindrical magnetron developed in the University of Greifswald, FRG. The system has been designed for experimental and computer-modelling studies of the DC discharge in crossed electric and magnetic fields in cylindrical geometry. In order to approach conditions close to an infinitely long system, and hence, to enable a more precise comparison with 1-D simulations, the ratio of the vessel length to the distance between the cathode and the anode has been chosen equal to 20. Six evenly distributed coils create the axial magnetic field. The homogeneity of the magnetic field ±0.2% has been achieved over the whole discharge vessel length 300 mm. The system is equipped with a rotable planar Langmuir probe movable in the radial direction. Measurements of the axial dependencies of plasma parameters are enabled by positioning the Langmuir probe in one of the 5 probe ports located between each couple of coils. We present the results of preliminary measurements of the radial and axial profiles of the plasma density and the mean electron energy.

Behnke, J. F.; Kudrna, P.; Rusz, J.; Tichý, M.

2000-03-01

418

Wire Wise.  

ERIC Educational Resources Information Center

Discusses how today's technology is encouraging schools to invest in furnishings that are adaptable to computer use and telecommunications access. Explores issues concerning modularity, wiring management, ergonomics, durability, price, and aesthetics. (GR)

Swanquist, Barry

1998-01-01

419

Novel Three-Component Rieske Non-Heme Iron Oxygenase System Catalyzing the N-Dealkylation of Chloroacetanilide Herbicides in Sphingomonads DC-6 and DC-2.  

PubMed

Sphingomonads DC-6 and DC-2 degrade the chloroacetanilide herbicides alachlor, acetochlor, and butachlor via N-dealkylation. In this study, we report a three-component Rieske non-heme iron oxygenase (RHO) system catalyzing the N-dealkylation of these herbicides. The oxygenase component gene cndA is located in a transposable element that is highly conserved in the two strains. CndA shares 24 to 42% amino acid sequence identities with the oxygenase components of some RHOs that catalyze N- or O-demethylation. Two putative [2Fe-2S] ferredoxin genes and one glutathione reductase (GR)-type reductase gene were retrieved from the genome of each strain. These genes were not located in the immediate vicinity of cndA. The four ferredoxins share 64 to 72% amino acid sequence identities to the ferredoxin component of dicamba O-demethylase (DMO), and the two reductases share 62 to 65% amino acid sequence identities to the reductase component of DMO. cndA, the four ferredoxin genes, and the two reductases genes were expressed in Escherichia coli, and the recombinant proteins were purified using Ni-affinity chromatography. The individual components or the components in pairs displayed no activity; the enzyme mixture showed N-dealkylase activities toward alachlor, acetochlor, and butachlor only when CndA-His6 was combined with one of the four ferredoxins and one of the two reductases, suggesting that the enzyme consists of three components, a homo-oligomer oxygenase, a [2Fe-2S] ferredoxin, and a GR-type reductase, and CndA has a low specificity for the electron transport component (ETC). The N-dealkylase utilizes NADH, but not NADPH, as the electron donor. PMID:24928877

Chen, Qing; Wang, Cheng-Hong; Deng, Shi-Kai; Wu, Ya-Dong; Li, Yi; Yao, Li; Jiang, Jian-Dong; Yan, Xin; He, Jian; Li, Shun-Peng

2014-08-15

420

An Advanced Fly-By-Wire Flight Control System for the RASCAL Research Rotorcraft: Concept to Reality  

NASA Technical Reports Server (NTRS)

Design features of a new fly-by-wire flight control system for the Rotorcraft-Aircrew Systems Concepts Airborne Laboratory (RASCAL) are described. Using a UH-60A Black Hawk helicopter as a baseline vehicle, the RASCAL will be a flying laboratory capable of supporting the research requirements of major NASA and Army guidance, control, and display research programs. The paper describes the research facility requirements of these pro-rams and the design implementation of the research flight control system (RFCS), with emphasis on safety-of-flight, adaptability to multiple requirements and performance considerations.

Rediess, Nicholas A.; Dones, Fernando; McManus, Bruce L.; Ulmer, Lon; Aiken, Edwin W. (Technical Monitor)

1995-01-01

421

80 ns/45 GHz Pulsed measurement system for DC and RF characterization of high speed microwave devices  

NASA Astrophysics Data System (ADS)

This paper presents a combined pulsed I(V)-pulsed RF state-of-the-art measurement system. Isothermal DC and AC measurement data can be achieved allowing a complete characterization and exploration of the safe operating area (SOA) of advanced SiGe:C HBTs. System behavior is explained in detail and reproduced by simulation taking into account the influence of all parasitic components. Optimization steps, system verification, measurement results and accuracy issues are presented.

Weiß, Mario; Fregonese, Sébastien; Santorelli, Marco; Sahoo, Amit Kumar; Maneux, Cristell; Zimmer, Thomas

2013-06-01

422

Transport properties of anomalous systems: Part A. Ultra thin Bi wires: Part B. A15 compounds  

Microsoft Academic Search

In the first part of this work, some theoretical aspects of the Quantum Size Effects (QSE) are discussed, namely some basics of the one-dimensional QSE and electron scattering on lattice vibrations in the presence of the QSE in both two- and one-dimensional cases. The experimental methods of making very thin (down to approximately 2000 A) single crystal wires of Bi

M. A. Gurvitch

1978-01-01

423

The impedance of a thin wire transmission line-dipole system with sinusoidal surface currents  

Microsoft Academic Search

Thin wire transmission lines and dipoles with diameters 2a which are much less than the operating wavelength ? carry essentially sinusoidally distributed surface currents. The Poynting vector method was used on a thin ?-gap fed dipole while retaining the sinusoidal surface current distribution. This present paper extends this work to the much more realistic case of the actual transmission line-dipole

R. H. MacPhie; K. Hui

1996-01-01

424

In-situ calibration of wire bonder ultrasonic system using integrated microsensor  

Microsoft Academic Search

Based on investigations with an ESEC thermosonic wire bonder, we report a novel ultrasound calibration method which consists of in-situ measurement of the friction heat generated by the gold ball as it scrubs on the oxide of an integrated microsensor. This procedure can be carried out in-process using a dedicated test chip and a modified clamping plate. The calibration dependence

Michael Mayer; Oliver Paul; Daniel Bolliger; Henry Baltes

1998-01-01

425

Spin–orbit coupling induced magnetoresistance oscillation in a dc biased two-dimensional electron system  

NASA Astrophysics Data System (ADS)

We study dc-current effects on the magnetoresistance oscillation in a two-dimensional electron gas with Rashba spin-orbit coupling, using the balance-equation approach to nonlinear magnetotransport. In the weak current limit the magnetoresistance exhibits periodical Shubnikov-de Haas oscillation with changing Rashba coupling strength for a fixed magnetic field. At finite dc bias, the period of the oscillation halves when the interbranch contribution to resistivity dominates. With further increasing current density, the oscillatory resistivity exhibits phase inversion, i.e., magnetoresistivity minima (maxima) invert to maxima (minima) at certain values of the dc bias, which is due to the current-induced magnetoresistance oscillation.

Wang, C. M.; Lei, X. L.

2014-06-01

426

Design and flight experience with a digital fly-by-wire control system in an F-8 airplane  

NASA Technical Reports Server (NTRS)

A digital fly-by-wire flight control system was designed, built, and for the first time flown in an airplane. The system, which uses components from the Apollo guidance system, is installed in an F-8 airplane as the primary control system. A lunar module guidance computer is the central element in the three-axis, single-channel, multimode, digital control system. A triplex electrical analog system which provides unaugmented control of the airplane is the only backup to the digital system. Flight results showed highly successful system operation, although the trim update rate was inadequate for precise trim changes, causing minor concern. The use of a digital system to implement conventional control laws proved to be practical for flight. Logic functions coded as an integral part of the control laws were found to be advantageous. Although software verification required extensive effort, confidence in the software was achieved.

Deets, D. A.; Szalai, K. J.

1974-01-01

427

The effects of water filtration systems on fluoride: Washington, D.C. metropolitan area.  

PubMed

According to the U.S. Environmental Protection Agency (EPA), approximately one in eight Americans is exposed to potentially harmful microbes, pesticides, lead, or radioactive radon whenever they drink a glass of tap water or take a shower. One reason for this exposure is that the water plants are aging or ill equipped to process the huge amounts of raw sewage and agricultural pollutants that are still being discharged into our drinking-water sources. Other compounds such as fluoride and chloride have been added to the community water supplies for health benefits. Water filtration systems are becoming more popular as people become concerned with pollutants in the public water supply and questions are being raised as to whether fluoride is affected by these filters. The aim of this pilot study was to assess the efficacy of three types of water filtration systems and to determine their impact on fluoride content of the water in the Washington, D.C. metropolitan area. One sample of water was collected daily for fourteen days, from one location. The sample was divided to use as a control and the test samples which were processed through various filter systems. With the use of a fluoride ion specific electrode, the fluoride concentration level was tested in all samples in order to determine the percentage of fluoride removed. This study was intended to prove that the water filtration systems did not affect the advantage offered by optimum water fluoride levels. The experimental samples were ascertained and compared to the control group, resulting in three of the four carbon filters showing statistically significant amounts of fluoride removed from the water. Both Reverse Osmosis and Distillation, as expected, removed the fluoride at a high rate. PMID:11068668

Jobson, M D; Grimm, S E; Banks, K; Henley, G

2000-01-01

428

Accessibility of the Metropolitan Washington, D.C. Public Transportation System to the Handicapped and Elderly.  

National Technical Information Service (NTIS)

Two hundred and fifty handicapped and/or elderly citizens from throughout the Metropolitan Washington, D.C., area were interviewed to determine their travel experiences. The survey findings, together with findings from an extensive search of research lite...

H. J. Kinley

1974-01-01

429

Composite superconducting wires obtained by high-rate tinning in molten Bi-Pb-Sr-Ca-Cu-O system  

NASA Technical Reports Server (NTRS)

Long lengths of metal superconductor composites were prepared by passing a copper wire through the bismuth based molten oxide system at a constant speed. The key to successful composite preparation is the high pulling speed involved, which permits minimization of the severe interaction between the unbuffered metal surface and the oxide melt. Depending on the temperature of the melt and the pulling speed, a coating with different thickness and microstructure appeared. The nonannealed thick coatings contained a Bi2(Sr,Ca)2Cu1O6 phase as a major component. After relatively short time annealing at 800 C, both resistivity and initial magnetization versus temperature measurements show superconducting transitions beginning in the 110 to 115 K region. The effects of annealing and composition on obtained results are discussed. This method of manufacture led to the fabrication of wire with a copper core in a dense covering with uniform thickness of about h approximately equal to 5 to 50 microns. Composite wires with h approximately equal to 10 microns (h/d approximately equal to 0.1) sustained bending on a 15 mm radius frame without cracking during flexing.

Grosav, A. D.; Konopko, L. A.; Leporda, N. I.

1991-01-01

430

Multimodule HVDC System Using SHE-PWM With DC Capacitor Voltage Equalization  

Microsoft Academic Search

Multimodule converter-based high-voltage dc (HVDC) power transmission incorporates numerous voltage-source converters (VSCs) connected in series\\/parallel to provide increased voltage\\/current and, hence, power ratings. When a selective harmonic elimination pulsewidth-modulation (SHE-PWM) technique is employed, the switching losses of the VSC modules are reduced but the voltages of the series-connected dc capacitors are not naturally balanced. In this paper, a voltage-balancing technique

Nikolas Flourentzou; Vassilios G. Agelidis

2012-01-01

431

Foundational model of structural connectivity in the nervous system with a schema for wiring diagrams, connectome, and basic plan architecture  

PubMed Central

The nervous system is a biological computer integrating the body's reflex and voluntary environmental interactions (behavior) with a relatively constant internal state (homeostasis)—promoting survival of the individual and species. The wiring diagram of the nervous system's structural connectivity provides an obligatory foundational model for understanding functional localization at molecular, cellular, systems, and behavioral organization levels. This paper provides a high-level, downwardly extendible, conceptual framework—like a compass and map—for describing and exploring in neuroinformatics systems (such as our Brain Architecture Knowledge Management System) the structural architecture of the nervous system's basic wiring diagram. For this, the Foundational Model of Connectivity's universe of discourse is the structural architecture of nervous system connectivity in all animals at all resolutions, and the model includes two key elements—a set of basic principles and an internally consistent set of concepts (defined vocabulary of standard terms)—arranged in an explicitly defined schema (set of relationships between concepts) allowing automatic inferences. In addition, rules and procedures for creating and modifying the foundational model are considered. Controlled vocabularies with broad community support typically are managed by standing committees of experts that create and refine boundary conditions, and a set of rules that are available on the Web.

Swanson, Larry W.; Bota, Mihail

2010-01-01

432

Bilateral second metatarsal stress fractures after hallux valgus correction with the use of a tension wire and button fixation system.  

PubMed

The pathomechanics and treatments of hallux valgus vary widely by deformity and surgeon, and are extensively described in the orthopedic and podiatric literature. With each newly described treatment, new complications can be encountered. In this report, we describe the case of a 22-year-old woman who underwent bilateral hallux valgus repair with a tension wire and button fixation system, and developed bilateral second metatarsal stress fracture at the point of fixation application during the postoperative period. Although this fixation system has been useful in our practice, like other surgical implants, it conveys a certain amount of risk that should be considered by surgeons using the device. PMID:20634102

Mader, David W; Han, Nancy M

2010-01-01

433

Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System  

SciTech Connect

A vacuum system with pressure in the low ultra-high vacuum (UHV) range is essential for long photocathode lifetimes in DC high voltage GaAs photoguns. A discrepancy between predicted and measured base pressure in the CEBAF photoguns motivated this study of outgassing rates of three 304 stainless steel chambers with different pretreatments and pump speed measurements of non-evaporable getter (NEG) pumps. Outgassing rates were measured using two independent techniques. Lower outgassing rates were achieved by electropolishing and vacuum firing the chamber. The second part of the paper describes NEG pump speed measurements as a function of pressure through the lower part of the UHV range. Measured NEG pump speed is high at pressures above 5×10^?11 Torr, but may decrease at lower pressures depending on the interpretation of the data. The final section investigates the pump speed of a locally produced NEG coating applied to the vacuum chamber walls. These studies represent the first detailed vacuum measurements of CEBAF photogun vacuum chambers.

M.L. Stutzman; P. Adderley; J. Brittian; J. Clark; J. Grames; J. Hansknecht; G.R. Myneni; M. Poelker

2007-05-01

434

Durability Evaluation of a Thin Film Sensor System With Enhanced Lead Wire Attachments on SiC/SiC Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

An advanced thin film sensor system instrumented on silicon carbide (SiC) fiber reinforced SiC matrix ceramic matrix composites (SiC/SiC CMCs), was evaluated in a Mach 0.3 burner rig in order to determine its durability to monitor material/component surface temperature in harsh environments. The sensor system included thermocouples in a thin film form (5 microns thick), fine lead wires (75 microns diameter), and the bonds between these wires and the thin films. Other critical components of the overall system were the heavy, swaged lead wire cable (500 microns diameter) that contained the fine lead wires and was connected to the temperature readout, and ceramic attachments which were bonded onto the CMCs for the purpose of securing the lead wire cables, The newly developed ceramic attachment features a combination of hoops made of monolithic SiC or SiC/SiC CMC (which are joined to the test article) and high temperature ceramic cement. Two instrumented CMC panels were tested in a burner rig for a total of 40 cycles to 1150 C (2100 F). A cycle consisted of rapid heating to 1150 C (2100 F), a 5 minute hold at 1150 C (2100 F), and then cooling down to room temperature in 2 minutes. The thin film sensor systems provided repeatable temperature measurements for a maximum of 25 thermal cycles. Two of the monolithic SiC hoops debonded during the sensor fabrication process and two of the SiC/SiC CMC hoops failed during testing. The hoops filled with ceramic cement, however, showed no sign of detachment after 40 thermal cycle test. The primary failure mechanism of this sensor system was the loss of the fine lead wire-to-thin film connection, which either due to detachment of the fine lead wires from the thin film thermocouples or breakage of the fine wire.

Lei, Jih-Fen; Kiser, J. Douglas; Singh, Mrityunjay; Cuy, Mike; Blaha, Charles A.; Androjna, Drago

2000-01-01

435

An electrochemical study of corrosion protection by primer-topcoat systems on 4130 steel with ac impedance and dc methods  

NASA Technical Reports Server (NTRS)

To investigate metal surface corrosion and the breakdown of metal protective coatings, the ac impedance method is applied to six systems of primer coated and primer topcoated 4130 steel. Two primers were used: a zinc-rich epoxy primer and a red lead oxide epoxy primer. The epoxy-polyamine topcoat was used in four of the systems. The EG and G-PARC Model 368 ac impedance measurement system, along with dc measurements with the same system using the polarization resistance method, were used to monitor changing properties of coated 4230 steel disks immersed in 3.5 percent NaCl solutions buffered at pH 5.4 over periods of 40 to 60 days. The corrosion system can be represented by an electronic analog called an equivalent circuit consisting of resistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for the resistors and capacitors, that can be assigned in the equivalent circuit following a least-squares analysis of the data, describe changes that occur on the corroding metal surface and in the protective coatings. Two equivalent circuits have been determined that predict the correct Bode phase and magnitude of the experimental sample at different immersion times. The dc corrosion current density data are related to equivalent circuit element parameters. Methods for determining corrosion rate with ac impedance parameters are verified by the dc method.

Mendrek, M. J.; Higgins, R. H.; Danford, M. D.

1988-01-01

436

Brake-By-Wire Program.  

National Technical Information Service (NTIS)

Two design iterations for electric calipers and two systems (full brake by wire and hybrid brakes) were developed for use on a ground vehicle. The program demonstrated a fully integrated-rated electric caliper and full brake- by-wire system on a sports ut...

R. J. Bowman P. F. Flanagan E. S. Baumgartner

2003-01-01

437

Voltage and Frequency Control for a Self-Excited Induction Generator Using a Three-Phase Four-Wire Electronic Converter  

Microsoft Academic Search

This work proposes a system, based on a self-excited induction generator (SEIG) with a shunt electronic converter, to feed isolated three-phase and single-phase linear or nonlinear loads. The electronic converter is composed by a three-phase four-wire shunt active filter and a DC chopper attached to its DC bus. The converter compensates the current harmonics, the reactive power and the load

JoseAntonio Barrado; R. Grino

2006-01-01

438

A fretting fatigue tester for steel wires and its measuring system  

Microsoft Academic Search

A self-made fretting fatigue tester for steel wire based on the computer-controlled electro-hydraulic servo fatigue testing machine is introduced in the paper. The working principle and experimental method are described. The signals of contact load, fretting tangential force and fretting amplitude are collected using force and displacement sensors. Synchronous acquisition and dynamic display of the signals of various parameters are

Dagang Wang; Xiaofan Jia; Dekun Zhang; Songquan Wang

2010-01-01

439

Clinical percutaneous imaging of coronary anatomy using an over-the-wire ultrasound catheter system  

Microsoft Academic Search

This manuscript describes initial applications of a unique new intravascular ultrasound imaging catheter. This 5.5F catheter uses an over-the-wire design and incorporates a phased array transducer at its tip. There are no moving parts. A 360° image is produced perpendicular to the catheter axis using a 20 MHz center frequency. A dedicated minicomputer is used for initial image processing, as

J. B. Hodgson; S. P. Graham; A. D. Savakus; S. G. Dame; D. N. Stephens; P. S. Dhillon; D. Brands; H. Sheehan; M. J. Eberle

1989-01-01

440

Microprocessor-based system for determining the thickness of conductors on printed wiring boards  

Microsoft Academic Search

A microprocessor-based, stored-program controller which incorporates a floating-point arithmetic unit to perform complex mathematical computations has been developed to determine the thickness of conductors on printed wiring boards. Conductor thickness is calculated from measured resistance by means of curve-fitting routines in the stored program. Called a film thickness calculator, the instrument provides a rapid, efficient, in-process, nondestructive means for determining

Hopwood

1977-01-01

441

University Wire  

NSDL National Science Digital Library

University Wire is a daily Internet news service for college newspapers. Included are a story of the day, a large list of pointers to Internet resources in topics such as current headlines, politics, medicine and health, and women's resources; a "Kopyedit Korner," with pointers to writing reference materials; a placement center with job openings lists for college journalists; a large selection of pointers to college newspapers; and pointers to general circulation newspapers. Pointers to student and professional journalism organizations, as well as a calendar of journalism related events, are also provided. University Wire is a service of The Main Quad.

1997-01-01

442

Analysis of a dc bus system with a nonlinear constant power load and its delayed feedback control  

NASA Astrophysics Data System (ADS)

This paper tackles a destabilizing problem of a direct-current (dc) bus system with constant power loads, which can be considered a fundamental problem of dc power grid networks. The present paper clarifies scenarios of the destabilization and applies the well-known delayed-feedback control to the stabilization of the destabilized bus system on the basis of nonlinear science. Further, we propose a systematic procedure for designing the delayed feedback controller. This controller can converge the bus voltage exactly on an unstable operating point without accurate information and can track it using tiny control energy even when a system parameter, such as the power consumption of the load, is slowly varied. These features demonstrate that delayed feedback control can be considered a strong candidate for solving the destabilizing problem.

Konishi, Keiji; Sugitani, Yoshiki; Hara, Naoyuki

2014-02-01

443

SamicaRound-an electrical insulation system for high-voltage motors with round wire windings up to 6.6 kV  

Microsoft Academic Search

Electrical motors made with round wire can be manufactured at lower costs and with minimized technological effort compared to machines with preformed windings. Whereas round wire windings are mostly applied in low-voltage machines, preformed windings are used for high-voltage motors. The development of the SamicaRound electrical insulation system enables motors of the traditional low-voltage design to operate up to 6.6

H. Brandes; W. Golbig; T. Hillmer; H. Klotsche; T. Partzsch; G. Wieland

2001-01-01

444

I. Theory of laser driven molecular wires. II. Light diffraction by colloidal crystals - numerical simulations for realistic finite systems using single scattering theory  

Microsoft Academic Search

Part I considers electron transport through a molecular bridge coupled to two metal electrodes in the presence of a monochromatic ac radiation field. Coherent current flow through the wire is calculated within a nondissipative one-electron tight binding model of the quantum dynamics. Using Floquet theory, the field-driven molecular wire is mapped to an effective time-independent quantum system characterized by a

Alexander Tikhonov

2006-01-01

445

Restoration Strategies for the South China Interconnected Power System after Generator Tripping following DC System Fault  

Microsoft Academic Search

When such severe contingency as double pole block fault arouses instability in the South China interconnected power system (SCIPS), selective tripping of generating units in the sending end has to be used as a method to maintain system stability. In case the tripped units go through a shutdown and cold start cycle for long duration, it is desirable that they

G. H. Cheng; Z. Xu; J. Chao

2006-01-01

446

Hy-wire and fast electric field change measurements near an isolated thunderstorm, appendix C  

NASA Technical Reports Server (NTRS)

Electric field measurements near an isolated thunderstorm at 6.4 km distance are presented from both a tethered balloon experiment called Hy-wire and also from ground based fast and slow electric field change systems. Simultaneous measurements were made of the electric fields during several lightning flashes at the beginning of the storm which the data clearly indicate were cloud-to-ground flashes. In addition to providing a comparison between the Hy-wire technique for measuring electric fields and more traditional methods, these data are interesting because the lightning flashes occurred prior to changes in the dc electric field, although Hy-wire measured changes in the dc field of up to 750 V/m in the direction opposite to the fair weather field a short time later. Also, the dc electric field was observed to decay back to its preflash value after each flash. The data suggest that Hy-wire was at the field reversal distance from this storm and suggest the charge realignment was taking place in the cloud with a time constant on the order of 20 seconds.

Holzworth, R. H.; Levine, D. M.

1983-01-01

447

Maximum power point tracking control and voltage regulation of a DC grid-tied wind energy conversion system based on a novel permanent magnet reluctance generator  

Microsoft Academic Search

This research paper aims to employ a new permanent magnet reluctance generator in a variable speed wind energy conversion system (WECS) of a grid-tied distributed generation application. The grid integration of WECS is achieved through cascaded dc-dc converters ensuring maximum power extraction from the wind energy while maintaining a constant output voltage at the grid side. The surplus power is

Kazmi Syed Muhammad Raza; Hiroki Goto; Hai-Jiao Guo; Osamu Ichinokura

2007-01-01

448

Energy and phase relaxation in non-equilibrium diffusive nano-wires with two-level systems  

Microsoft Academic Search

In recent experiments the non-equilibrium distribution function ƒ(E,U) in diffusive Cu and Au quantum wires at a transport voltage U shows scaling behavior, ƒ(E,U)=ƒ(E\\/eU), indicating a non-Fermi liquid interaction with non-vanishing\\u000a T=0 scattering rate. The two-channel Kondo (2CK) effect, possibly produced by degenerate two-level systems, is known to exhibit\\u000a such behavior. Generalizing the auxiliary boson method to non-equilibrium, we calculate

Johann Kroha

2001-01-01

449

Flying wires at Fermilab  

SciTech Connect

Transverse beam profile measurement systems called ''Flying Wires'' have been installed and made operational in the Fermilab Main Ring and Tevatron accelerators. These devices are used routinely to measure the emittance of both protons and antiprotons throughout the fill process, and for emittance growth measurements during stores. In the Tevatron, the individual transverse profiles of six proton and six antiproton bunches are obtained simultaneously, with a single pass of the wire through the beam. Essential features of the hardware, software, and system operation are explained in the rest of the paper. 3 refs., 4 figs.

Gannon, J.; Crawford, C.; Finley, D.; Flora, R.; Groves, T.; MacPherson, M.

1989-03-01

450

30 CFR 77.705 - Guy wires; grounding.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Guy wires; grounding. 77.705 Section 77...OF UNDERGROUND COAL MINES Grounding § 77.705 Guy wires; grounding. Guy wires from poles...securely connected to the system ground or be provided...

2013-07-01

451

Performance analysis of fuzzy logic controller based DC-DC converter fed DC series motor  

Microsoft Academic Search

A fuzzy controller for closed loop control of DC drive fed by DC-DC converter (Chopper) is designed and presented in this paper. This system has been designed to have two loops with an inner ON\\/OFF current controller and an outer fuzzy speed controller. The later is used to change the duty cycle of the converter and thereby, the voltage fed

M. Muruganandam; M. Madheswaran

2009-01-01

452

Back-action noise in strongly interacting systems: the dc SQUID and the interacting quantum point-contact  

Microsoft Academic Search

We study the back-action noise and measurement efficiency (i.e. noise\\u000atemperature) of a dc SQUID amplifier, and equivalently, a quantum point contact\\u000adetector formed in a Luttinger liquid. Using a mapping to a dissipative\\u000atight-binding model, we show that these systems are able to reach the quantum\\u000alimit even in regimes where several independent transport processes contribute\\u000ato the current.

A. A. Clerk

2005-01-01

453

Nonlinear theory of fractional microwave-induced magnetoresistance oscillations in a dc-driven two-dimensional electron system  

Microsoft Academic Search

Microwave-induced nonlinear magnetoresistance in a dc-driven two-dimensional electron system is examined using a multi-photon-assisted transport scheme directly controlled by the current. It is shown that near the second subharmonic of the cyclotron resonance, the frequency of the resistivity oscillation with the magnetic-field-normalized current density is double that at the cyclotron resonance and its harmonics, in excellent agreement with recent experimental

X. L. Lei

2009-01-01

454

Brushless DC motor drives supplied by PV power system based on Z-source inverter and FLIC MPPT controller  

Microsoft Academic Search

This paper discusses operation performance of a water pumping system consist of a brushless dc (BLDC) motor coupled a centrifugal pump and accompanying a Z-source inverter (ZSI) fed by a photovoltaic (PV) array, to be improved. Despite conventional double-stage power converters, this paper proposes utilizing a single-stage ZSI to extract the maximum power of the PV array and supply the

S. A. K. H. Mozaffari Niapour; S. Danyali; M. B. B. Sharifian; M. R. Feyzi

2011-01-01

455

Dynamic Model and Control of AC–DC–AC Voltage-Sourced Converter System for Distributed Resources  

Microsoft Academic Search

This paper introduces a dynamic model of the ac-dc-ac voltage-sourced converter (VSC) system which provides a linear relationship between the input and output variables. The model is developed in two steps. First, the exact abc frame switched model of a VSC is transformed to a switching reference frame (SRF). Then, the SRF model is transformed to an appropriate dq0 reference

H. Nikkhajoei; R. Iravani

2007-01-01

456

In vitro system for studying interactions between Citrus exocortis viroid and Gynura aurantiaca (Blume) DC. metabolism and growing conditions  

Microsoft Academic Search

Citrus exocortis viroid (CEVd) is an economically important plant pathogen, which infects a broad range of hosts. In order to investigate complex interactions among viroid, host-growing conditions, and plant secondary metabolism, we setup an in vitro system for the cultivation of CEVd-infected and viroid-free Gynura aurantiaca (Blume) DC. shoots. Both basal Murashige and Skoog (MS) medium and MS medium supplemented

Silvija ?erni; Mirna ?urkovi?-Perica; Gordana Rusak; Dijana Škori?

2012-01-01

457

In vitro system for studying interactions between Citrus exocortis viroid and Gynura aurantiaca (Blume) DC. metabolism and growing conditions  

Microsoft Academic Search

Citrus exocortis viroid (CEVd) is an economically important plant pathogen, which infects a broad range of hosts. In order to investigate complex interactions among viroid, host-growing conditions, and plant secondary metabolism, we setup an in vitro system for the cultivation of CEVd-infected and viroid-free Gynura aurantiaca (Blume) DC. shoots. Both basal Murashige and Skoog (MS) medium and MS medium supplemented

Silvija ?erni; Mirna ?urkovi?-Perica; Gordana Rusak; Dijana Škori?

2011-01-01

458

The Geostationary Operational Satellite R Series SpaceWire Based Data System Architecture  

NASA Technical Reports Server (NTRS)

The GOES-R program selected SpaceWire as the best solution to satisfy the desire for simple and flexible instrument to spacecraft command and telemetry communications. Data generated by GOES-R instruments is critical for meteorological forecasting, public safety, space weather, and other key applications. In addition, GOES-R instrument data is provided to ground stations on a 24/7 basis. GOES-R requires data errors be detected and corrected from origin to final destination. This paper describes GOES-R developed strategy to satisfy this requirement

Krimchansky, Alexander; Anderson, William H.; Bearer, Craig

2010-01-01

459

Synchronous operation of dual-inverter-based photovoltaic system with low DC-voltages  

Microsoft Academic Search

Novel method of synchronized pulsewidth modulation (PWM) has been disseminated for control of cascaded (dual) inverters of photovoltaic installation with relatively low DC-voltages of two insulated photovoltaic panels, operating under condition of low level of solar irradiance. Control regimes are characterized by overmodulation control modes of two inverters in this case. Algorithms of synchronized PWM provide continuous voltage synchronization both

G. Griva; V. Oleschuk

2010-01-01

460

A high frequency link direct dc-ac converter for residential fuel cell power systems  

Microsoft Academic Search

This paper describes a boost converter cascaded high frequency link direct dc-ac converter suitable for fuel cell power sources. A new multi-loop control for a boost converter to reduce the low frequency input current harmonics drawn from the fuel cell is proposed. A new PWM technique for the cycloconverter at the secondary to reject the low order harmonics in the

Yu Jin Song; Prasad N. Enjeti

2004-01-01

461

Application of optical fiber DC current transformer for railway power system measurement and protection  

Microsoft Academic Search

A novel optical fiber DC current transformer (OFDCCT) with advantages of robustness to the electromagnetic field, flexibility to the install condition, simple structure and electrical insulation has been developed. In this paper, some measurement results which are difficult to be realized by a conventional current sensor are shown. Such results emphasize the advantages of the OFDCCT. Furthermore, the possible future

Hitoshi HAYASHIYA; Takehiko NAKAMURA; Syuichi NAGAI; Hajime INOUE

2009-01-01

462

Aircraft wiring program status report  

Microsoft Academic Search

In this Naval Air Warfare Center (NAWC) Aircraft Division status report, the general and wire and cable component activities, the systems engineering activities, the aircraft wiring lead maintenance activities, the NAVAIR\\/NASA interface activities, and the Base Realignment and Closure (BRAC) Commission recommendations are presented.

Rex Beach

1995-01-01

463

Aircraft wiring program status report  

NASA Technical Reports Server (NTRS)

In this Naval Air Warfare Center (NAWC) Aircraft Division status report, the general and wire and cable component activities, the systems engineering activities, the aircraft wiring lead maintenance activities, the NAVAIR/NASA interface activities, and the Base Realignment and Closure (BRAC) Commission recommendations are presented.

Beach, Rex

1995-01-01

464

DC Electronics  

NSDL National Science Digital Library

This is a website with many learning objects on DC Electronics with over 60 lessons in areas including: Basic Concepts, Electrical Circuits / Meters, Ohm's Law, Magnetism, Parallel Circuits, Series/Parallel Circuits, Series/Parallel Applications and Series Circuits.

2012-10-18

465

Theoretical development and experimental verification of a DC-AC electronically rectified load-generator system model compatible with common network analysis software packages  

Microsoft Academic Search

A method for modeling electronically commutated DC-AC load-rectifier-generator systems is presented. The method is based on a modified form of Park's d-q-o transformation, and yields an equivalent system network which is compatible with most commonly known network analysis software packages. The method was used to develop a model for the simulation of the dynamic steady-state performance of a DC-AC system

A. A. Arkadan; T. J. Hijazi; N. A. Demerdash; J. G. Vaidya; V. K. Maddali

1988-01-01

466

Wiring and Cabling  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education program, this module introduces students to wiring and cabling principles, including transmission lines, computer network and wireless systems, and troubleshooting. The Knowledge Probes allow students to answer open-ended questions covering the content of the module, and the Learning Resources present activities, laboratories, and games to further solidify the material. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource for vocational electronics educators as a ready-made classroom introduction to wiring and cabling.

2008-12-08

467

Wires by Patchy Particles  

NSDL National Science Digital Library

Simulation Software: Glotzer Group Code Simulation Method: Brownian Dynamics A system of 80 spherical particles with two patches at a concentration of 0.20, was run starting at an effectively infinite temperature then instantaneously quenched to a temperature of 0.5. The final equillibrium structure is wires or chains. Simulation Model: United Atom Rigid Body with Lennard-Jones

Zhang, Zhenli

2005-01-31

468

Radiation effects on DC-DC Converters  

NASA Technical Reports Server (NTRS)

DC-DC switching converters are circuits that can be used to convert a DC voltage of one value to another by switching action. They are increasing being used in space systems. Most of the popular DC-DC switching converters utilize power MOSFETs. However power MOSFETs, when subjected to radiation, are susceptible to degradation of device characteristics or catastrophic failure. This work focuses on the effects of total ionizing dose on converter performance. Four fundamental switching converters (buck converter, buck-boost converter, cuk converter, and flyback converter) were built using Harris IRF250 power MOSFETs. These converters were designed for converting an input of 60 volts to an output of about 12 volts with a switching frequency of 100 kHz. The four converters were irradiated with a Co-60 gamma source at dose rate of 217 rad/min. The performances of the four converters were examined during the exposure to the radiation. The experimental results show that the output voltage of the converters increases as total dose increases. However, the increases of the output voltage were different for the four different converters, with the buck converter and cuk converter the highest and the flyback converter the lowest. We observed significant increases in output voltage for cuk converter at a total dose of 24 krad (si).

Zhang, Dexin; Attia, John O.; Kankam, Mark D. (Technical Monitor)

2000-01-01

469

Early detection of influenza outbreaks using the DC Department of Health's syndromic surveillance system  

PubMed Central

Background Since 2001, the District of Columbia Department of Health has been using an emergency room syndromic surveillance system to identify possible disease outbreaks. Data are received from a number of local hospital emergency rooms and analyzed daily using a variety of statistical detection algorithms. The aims of this paper are to characterize the performance of these statistical detection algorithms in rigorous yet practical terms in order to identify the optimal parameters for each and to compare the ability of two syndrome definition criteria and data from a children's hospital versus vs. other hospitals to determine the onset of seasonal influenza. Methods We first used a fine-tuning approach to improve the sensitivity of each algorithm to detecting simulated outbreaks and to identifying previously known outbreaks. Subsequently, using the fine-tuned algorithms, we examined (i) the ability of unspecified infection and respiratory syndrome categories to detect the start of the flu season and (ii) how well data from Children's National Medical Center (CNMC) did versus all the other hospitals when using unspecified infection, respiratory, and both categories together. Results Simulation studies using the data showed that over a range of situations, the multivariate CUSUM algorithm performed more effectively than the other algorithms tested. In addition, the parameters that yielded optimal performance varied for each algorithm, especially with the number of cases in the data stream. In terms of detecting the onset of seasonal influenza, only "unspecified infection," especially the counts from CNMC, clearly delineated influenza outbreaks out of the eight available syndromic classifications. In three of five years, CNMC consistently flags earlier (from 2 days up to 2 weeks earlier) than a multivariate analysis of all other DC hospitals. Conclusions When practitioners apply statistical detection algorithms to their own data, fine tuning of parameters is necessary to improve overall sensitivity. With fined tuned algorithms, our results suggest that emergency room based syndromic surveillance focusing on unspecified infection cases in children is an effective way to determine the beginning of the influenza outbreak and could serve as a trigger for more intensive surveillance efforts and initiate infection control measures in the community.

2009-01-01

470

Introducing measure-by-wire, the systematic use of systems and control theory in transmission electron microscopy.  

PubMed

Transmission electron microscopes (TEMs) are the tools of choice for academic and industrial research at the nano-scale. Due to their increasing use for routine, repetitive measurement tasks (e.g., quality control in production lines) there is a clear need for a new generation of high-throughput microscopes designed to autonomously extract information from specimens (e.g., particle size distribution, chemical composition, structural information, etc.). To aid in their development, a new engineering perspective on TEM design, based on principles from systems and control theory, is proposed here: measure-by-wire (not to be confused with remote microscopy). Under this perspective, the TEM operator yields the direct control of the microscope's internal processes to a hierarchy of feedback controllers and high-level supervisors. These make use of dynamical models of the main TEM components together with currently available measurement techniques to automate processes such as defocus correction or specimen displacement. Measure-by-wire is discussed in depth, and its methodology is illustrated through a detailed example: the design of a defocus regulator, a type of feedback controller that is akin to existing autofocus procedures. PMID:21945998

Tejada, Arturo; den Dekker, Arnold J; Van den Broek, Wouter

2011-11-01

471

DC++: distributed object-oriented system support on top of OSF DCE  

Microsoft Academic Search

The OSF Distributed Computing Environment (DCE) is becoming an industry standard for open distributed computing. However, DCE only supports client\\/server-style applications based on the remote procedure call (RPC) communication model. This paper describes the design and imple- mentation of an extended distributed object-oriented environment, DC++, on top of DCE. As op- posed to RPC, it supports a uniform object model,

Alexander Schill; Markus U. Mock

1993-01-01

472

Researches on the Noise Models of Valves and DC PLC Filters in UHVDC Transmission Project  

Microsoft Academic Search

Ultra-high voltage direct current (UHVDC) converter stations produce high levels of carrier frequency noise which can cause harmful interference to power-line carrier and open-wire carrier systems. The noise models of converter valves and converters arranged with two 12-pulse valve groups in series per pole are given. Calculation results of noise interference on dc pole line and electrode line for the

Wen Jun; Xu Chao; Han Min-xiao; Zheng Jin; Yin Wei-yang; Sun Zhong-ming

2008-01-01

473

Trip wire detection using polarimetric IR  

Microsoft Academic Search

In this paper we present a method for passive stand off detection of trip wires. The concept described has the ability to detect trip wires camouflaged in a wide variety of natural backgrounds. The system includes an IR camera using the 3-5 micron band and a polarizing filter. A simple software algorithm is used to dewarp the trip wire in

Jesper Storm; Tommy Geisler

2000-01-01

474

An improved ac\\/dc current comparator  

Microsoft Academic Search

A novel design of the magnetic cores, windings and means of the excitation and detection for an improved ac\\/dc current comparator is disclosed. The system enables accurate measurements of ac current only or dc current only, or both simultaneous ac and dc current with a pair of detection cores and windings only. For the same order sensitivity of ac\\/dc current

Shiyan Ren; Shengneng She; Xusheng Chen

1995-01-01

475

Welding wire pressure sensor assembly  

NASA Technical Reports Server (NTRS)

The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

Morris, Timothy B. (inventor); Milly, Peter F., Sr. (inventor); White, J. Kevin (inventor)

1994-01-01

476

Design research on the conductor of 10 kA class HTS DC power cable  

NASA Astrophysics Data System (ADS)

High temperature superconducting (HTS) DC power cable shows a wide application prospect in the field of power transmission for its nearly lossless and rather high capacity. A 360 m/10 kA HTS DC power cable system, which connects the rectifier output of a substation with the bus bar of an electrolytic aluminium cell, will be put into operation at Henan Zhongfu Industrial Co., Ltd. As one of the items in this project, a 5 m/10 kA HTS DC power cable was developed, which is used to investigate the conductor design, fabrication, current-carrying capacity and stability of the 360 m/10 kA HTS power cable. The HTS DC power cable core consists of five conductor layers wound with spliced Bi-2223 wires with the length of 600 m. The cable core has five layers and 23 conductors in each layer with the outer diameter of 45.42 mm. The superconducting power cable is fabricated and tested. The critical current is about 14.3 kA at 77 K. The superconducting power cable is charged to 10 kA with rate of 10 A/s and operates at steady-state for 30 min. In this paper, the 10 kA HTS DC power cable design, fabrication and test are presented. The experimental research of the performance of spliced superconducting wire and charging, steady-state operating performance of the cable was carried out.

Zhang, Dong; Dai, Shaotao; Zhang, Fengyuan; Huang, Tianbin; Wang, Yinshun; Lin, Yubao; Teng, Yuping; Zhang, Guomin; Xiao, Liye; Lin, Liangzhen

2012-12-01

477

Nonlinear theory of fractional microwave-induced magnetoresistance oscillations in a dc-driven two-dimensional electron system  

Microsoft Academic Search

Microwave-induced nonlinear magnetoresistance in a dc-driven two-dimensional\\u000aelectron system is examined using a multi-photon-assisted transport scheme\\u000adirect controlled by the current. It is shown that near the 2nd subharmonic of\\u000athe cyclotron resonance, the frequency of the resistivity oscillation with the\\u000amagnetic-field-normalized current-density is double that at the cyclotron\\u000aresonance and its harmonics, in excellent agreement with recent experimental\\u000afindings

X. L. Lei

2009-01-01

478

DC Transformer.  

National Technical Information Service (NTIS)

A component level dc transformer is described in which no alternating currents or voltages are present. It operates by combining features of a homopolar motor and a homopolar generator, both de devices, such that the output voltage of a de power supply ca...

C. M. Ihlefeld R. C. Youngquist S. O. Starr

2013-01-01

479

DC Biotech  

NSDL National Science Digital Library

DC Biotech is a student-centered project dedicated to encourage and assist Washington DC public school students to pursue careers in the rapidly growing, multi-billion dollar Biotechnology industry. DCBiotech's NSF award states: "The DC Biotech project is creating a Washington, DC area consortium to improve student competencies in science, broaden students' career opportunities, and improve biotechnology workforce diversity. Project Objectives include providing professional development for teachers including research opportunities, summer training, online coursework, and in-school/class mentoring so they can prepare their students for the biotech workplace; providing support for students to intern to gain experience in a professional workplace; establishing, with the DCPS Office of Career and Technical Education (OCTE) and our workplace partners, a certificate of employability in biotechnology; establishing, with OCTE and Montgomery College, coursework articulation that will prepare graduates of the high school biotech program for further study. The site currently only provides information on the project but looks to add resources for both students and teachers in the future.

2008-08-11

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Fabrication of Bi?Pb?Sr?Ca?Cu?O superconducting composite wires with copper core  

NASA Astrophysics Data System (ADS)

By passing a flexible copper wire through the molten Bi?Pb?Sr?Ca?Cu?O system at a high constant speed, long lengths of composite wires were prepared. Depending on the pulling speed and the temperature of the melt, a coating with different microstructure and thickness from less than ten to several tens of microns can be obtained. The short samples cut out of the composite wires thus obtained were annealed in air in a preheated furnace. After relatively short-time annealing at 800°C, both resistivity and d.c. magnetization versus temperature measurements show indications of onset of superconductivity in the 110-115 K region; zero resistance was achieved in the range 65-70 K.

Grozav, A. D.; Konopko, L. A.; Leporda, N. I.; Onu, M. I.; Panaitov, G. I.

1990-11-01