• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.41-45
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• 2011

Hybrid fault current limiters (FCL) have been researched at Yonsei University. The hybrid FCL has advantages such as having a rapid response to a sudden fault situation and a fast recovery time from a quench. It consists of an asymmetric HTS coil, a switching module, and a bypass reactor. The asymmetric HTS coil is wound with two different types of HTS wires in an opposite direction so that it has nearly zero inductance at the superconducting state. When the quench occurs at the fault state, a strong magnetic field is generated from the asymmetric coil because of different quench characteristics of two HTS wires, and then a repulsive force is induced in the switching module. The force opens the switch and the fault current is pushed into the bypass reactor. In this research, we analyzed the cause of the repulsive force and confirmed, experimentally and computationally, that the magnitude of a repulsive force is varied by changing the gap distance between the asymmetric coil and the switching module. By using the FEM simulation, we calculated the repulsive force with respect to the gap distance and verified that the effect of the gap distance. Then, short circuit test was carried out to confirm the correct operation of the fast switch.

• 전력전자학회논문지
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• 제26권1호
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• pp.25-31
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• 2021

This paper describes the design of a power cell-based pulsed power modulator with fast rise times. The pulse-generating section of the pulse power modulator is a series stack of power cells. Each power cell is composed of a storage capacitor, a pulse switch, and a bypass diode. When the pulse switches are turned on, the capacitors are connected in series and the sum of voltages is applied to the load. For output pulses with fast rise times, an IGBT with fast turn-on characteristics is adopted as a pulse switch and the optimized gate driving method is used. Pspice simulation is performed to account for the gate driving method. A 10 kV, 12-power cell-based pulsed power modulator is tested under resistive load and plasma reactor load. The rise times of output pulses less than 20 ns are confirmed, showing that the pulsed power modulator can be effectively applied to pulsed power applications with fast rise times.

• 한국초전도ㆍ저온공학회논문지
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• 제9권3호
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• pp.57-61
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• 2007

The current limiting characteristics of hybrid SFCL with additional power electronic devices was investigated in order to improve operation reliabilities. The hybrid SFCL developed consists of a superconducting trigger (S/T) part, a fast switch (F/S) module and a current limiting (C/L) part. Although hybrid SFCL had shown a excellent current limiting characteristics, this device was rather vulnerable to the residual arc currents which could exist during fast switch operation. This undesirable arc should be extinguished as quickly as possible in order to implement perfect fault current commutation. So, in order to eliminate the residual arcs between fast switch contacts, the power electronic devices (IGBT or GTO) were connected in series between the S/T part and the interrupter of the F/S module. According to the fault tests conducting with an input voltage of $270\;V_{rms}$ and a fault current of $5\;kA_{rms}$, The power electronic devices could perfectly remove the arc generated between the contacts of the interrupter within 4 ms after the fault occurred. From the test analysis, it was confirmed that the hybrid SFCL could enhance the operation reliability by adopting additional power electronic devices.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.207-210
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• 2002

We had designed thermally controlled superconducting switches using a general nonlinear optimized algorithm with constraints and tested its performance. Objective function was to minimize the total volume of the superconducting switch. And constraints were to have designed resistance in normal status and temperature. In order to compare performance of the optimized superconducting switch, we made another one which had geometrically different parameters but had same structure and resistance value when the superconductor part is normal status by heater. Objective function converged very rapidly. As result, volume of the adiabatic part and total volume of the switch were reduced to more than 70% and 30% respectively. Also, even if same heater power was supplied with NiCr wire heater, the optimized superconducting switch had very fast On-OFF switching performance comparing with unoptimized switch.

• E2M - 전기 전자와 첨단 소재
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• 제7권3호
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• pp.213-219
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• 1994

Cu compensated Si doped GaAs (GaAs :Si:Cu has been chosen as the switch material. The GaAs material has been characterized by DLTS(Deep Level Transient Spectroscopy) technique and the obtained data were used in the computer simulation. Simulation studies are performed on several GaAs switch systems, composed of different densities of Cu, to investigate the influence of deep traps in the switch systems. The computed results demonstrates important aspect of the switch, the existence of two stable states and fast optical quenching. An important parameter optimum Cu density for the switch are also determined.

• ETRI Journal
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• 제31권5호
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• pp.593-597
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• 2009

In this paper, we present a spatial perturbation method to control the optical patterns in semiconductor microresonators in the far-field configuration. We propose a fast all-optical switch which operates at a low light level. The switching beam controls the behavior of output beams with strong intensities. The method has been applied successfully to different optical patterns such as rolls, squares, and hexagons.

• 대한산업공학회지
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• 제22권2호
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• pp.277-302
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• 1996

The overall performance of BISDN depends significantly on the interconnection network or the switch fabric. Hence, it is extremely important to evaluate the performance of the network or the fabric. The well developed performance models also provide insight into the factors that determine design tradeoffs as well as quantitative estimates of their importance. The objective of this paper is to investigate and critically compare all the developed performance analysis models of FPS according to internal switch fabric structure, traffic assumptions, performance measures, methodologies, etc. FPSs are described according to their internal fabric structure. Brief history of FPS performance analysis is mentioned and performance analysis modeling is discussed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.277-279
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• 2008

In this paper, a novel active boost converter for SR drive is proposed. An active capacitor circuit is added in the front-end. Based on this active capacitor network, when boost switch turns off, this network seems as passive capacitor network. And the voltage of boost capacitor can keep balance with dc-link voltage automatically. In the capacitor network, discharging voltage is general dc-link voltage in parallel-connected capacitors; charging voltage is double dc-link voltage in series-connected capacitors. When boost switch turns on, two capacitors are connected in series, and discharging voltage is up to double dc-link voltage. So the fast excitation current can be obtained from this mode. Profit from fast excitation and fast demagnetization mode, the performance and output power can be improved. Some computer simulations are done to verify the performance of proposed converter.

• 전력전자학회논문지
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• 제8권1호
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• pp.24-29
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• 2003

현재 120kV/70A 고압 스위치가 KSTAR의 NBI 시스템에 사용되기 위하여 대전의 원자력 연구소에 설치되어 있다. NBI 시스템은 아크 발생시 이온 소스를 보호하기 위하여 전압의 빠른 차단 및 빔 전류의 유시를 위하여 전압의 빠른 턴온이 요구된다. 따라서 고압 스위치와 아크 검출회로는 NBI 시스템에서 중요한 부분을 차지하고 있다. 고압의 반도체 스위치는 NBI 시스템 뿐만 아니라 산업전반에서 요구되고 있다. NBI 시스템에 적용된 120kV/70A 고압 스위치는 100개의 MOSFET 소자를 직렬연결하였으며 본 논문에서 제안한 바이어스 전원이 없는 간단한 구동회고를 사용하였다. 실험식에서의 시험 및 현장에서 100kW의 모의 저항부하와 NBI 이온 소스에 적용한 실험결과를 제시하였다. 본 논문은 120kV/70A 고압 MOSFET 스위치와 간단한 게이트 구동회로의 설계를 제시하였으며, 제작 및 시험기간 동안의 문제점 및 해결방안에 대해서도 제시하였다.

• 전력전자학회논문지
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• 제9권2호
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• pp.126-133
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• 2004

본 연구에서는 저 비용 응용분야에 적합한 4스위치 3상 BLDC 전동기의 새로운 전류 제어 알고리즘을 제안하였다. 4스위치 시스템에서 빠른 속도 및 토크 응답 그리고 적은 토크 리플과 같은 좋은 동작 특성을 얻기 위한 기준 전류 발생 기법을 제안하였다. 특히, 제안한 기법은 전류 전환시 발생되는 토크 리플을 현저히 저감시켜 4스위치 시스템을 산업 응용 분야에 보다 널리 적용할 수 있을 것으로 기대한다.