• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1947-1949
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• 1999

Carrier lifetime in silicon power devices caused switching delay and excessive power loss at high frequency switching. We studied transient turn-on/turn-off transient characteristics of electron irradiated and proton irradiated silicon pn junction diodes. Both the electron and proton irradiation of power devices have already become a widely used practice to reduce minority carrier lifetime locally[1]. The sample is n+p junction diode, made by ion implantation on a $20\Omega.cm$ p-type wafer. We investigated turn-on/turn-off transient & breakdown voltage characteristics by digital oscilloscope. Our data show that proton irradiated samples show better performance than electron irradiated samples.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권7호
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• pp.339-350
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• 2002

Pole arcs, turn-on angle, and turn-off angle are major design factors, which affects Switched Reluctance Motor's torque performance. If these design factors are considered independently, the enhancement of SRM performance is restricted. Therefore, we need to consider pole arcs, turn-on angle and turn-off angle at the same time, when we design SR. In this paper, we analyze how these factors affect to torque ripple and average torque by using dynamic Finite Element Method(FEM) with derive circuit and present the good design results according to the various speeds. Especially, we formulate turn-on and turn-off angle from a voltage equation and present effective design range.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.773-776
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• 1993

The thyristor turn-off model plays an important part in the design of thyristor snubber circuit. However, it is difficult to determine the thyristor turn-off characteristics. In this paper two methods to establish the simple thyristor turn-off model are proposed based on the reverse recovery characteristics given in the data sheets. Using the simple thyristor turn-off model, the optimum thyristor snubber circuit design procedures are presented considering maximum voltage spike, maximum reverse dv/dt, and turn-off loss.

• Journal of Power Electronics
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• 제7권1호
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• pp.81-88
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• 2007

This paper presents a new approach to the automatic control of the turn-off angle used to excite the Switched Reluctance Motor (SRM) employed in electric vehicles (EV). The controller selects the turn-off angle that supports and improves the performance of the motor drive system. This control scheme consisting of classical current control and speed control depends on a lookup table to take the best result of the motor. The turn-on angle of the main switches of the inverter is fixed at $0^{\circ}C$ and the turn-off angle is variable depending on the reference speed. The motor, inverter and control system are modeled in Simulink to demonstrate the operation of the system.

• 조명전기설비학회논문지
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• 제16권5호
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• pp.61-65
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• 2002

SRM 토크는 인덕턴스 프로파일과 전류에 의해 발생한다. 발생한 SRM 토크는 전류제어시 turn-off 각을 제어함으로써 최대화 할 수 있고, 본 논문에서는 최소자승법을 이용하여 구한 함수를 통해 Turn-off 각을 제어할 수 있는 방안을 제안하였다. 시뮬레이션은 3상 6/4극 SRM을 대상으로 하였고, 제안한 방법에 의해 최대 평균토크가 됨을 시뮬레이션을 통해 증명하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.351-354
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• 2001

In this paper, we present self-tuning control of switched reluctance motor for maximum torque with phase current and shaft position sensor. Determination method of turn-on/off angle is realized by using self-tuning control method. During the sampling time, micro-controller checks the number of pulse from encoder and compare with the number of pre-checked pulse. After micro-controller calculates between two data, it moves forward or backward turn-off angle. When the turn-off angle is fixed optimal turn-off angle, the turn-on angle automatically moves forward or backward by a step using self-tuning control method. And then, optimal turn-off angle is searched once again. As such a repeating process, turn-on/off angle is moved automatically to obtain the maximum torque. The experimental results are presented to validate the self-tuning algorithm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.357-360
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• 2003

In this paper, we designed 4.5kV/1.5kA IGCT devices. GCT thyristor has many superior characteristics compared with GTO thyristor, for examples; snubberless turn-off capability, short storage time, high turn-on capability, small turn-off gate charge and low total power loss of the application system containing device and peripheral parts such as anode reactor and snubber capacitance. In this paper we designed GCT thyristor devices, and analyzed static and dynamic characteristics of GCT thyristor depending on the minority carrier lifetime, n-base thickness and doping concentration of n-base region, respectively. Especially, turn-on and turn-off characteristics are very important characteristics for GCT thyristor devices. So, we considered above characteristic for design and analysis of GCT devices.

• 전력전자학회논문지
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• 제3권4호
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• pp.418-425
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• 1998

본 논문에서는 위상각 제어에서 주어진 턴온 각에서 최대의 토크를 유지하기 위한 적절한 턴오프 각을 자기동조방식(self-tuning method)에 의해 결정하는 방식을 제안하였다. 엔코더에 의해 샘플링 시간(sampling time)동안 구해진 펄스 수는 바로 이전의 샘플링시간 동안 구해진 펄스 수와 비교하여 턴오프 각을 앞으로 또는 뒤로 이동한다. 이러한 과정을 되풀이함으로서 최대 토크를 발생하는 턴오프 각을 결정하게 된다. 실제 회로에서는 원 칩 마이크로프로세서에 의해 처리되었으며 실험을 통해 턴온 각이 변하더라도 자기동조방식에 의해 턴오프 각을 조정하면 빠른 속도가 유지됨을 보여 주었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권7호
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• pp.356-363
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• 2001

A SRG (Switched Reluctance Generator) has many advantages such as high efficiency, low cost, high-speed capability and robustness compared with other of machine. But the control methods that have been adopted for SRGs are complicated. This paper proposes a simple control method using the PID controller which only controls turn-off angles while keeping turn-on angles of SRG constant. In order to keep the output voltage constant, the turn-off angle for load variations is controlled by using linearity between the generated current and turn-off angle since the reference generated current can be led through the voltage errors between the reference and the actual voltage. The suggested control method enhances the robustness of this system and simplifies the hardware and software by using only the voltage and the speed sensors. The proposed method is verified by experiments.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.501-506
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• 2022

Long turn-off time limits high frequency operation of Bipolar Junction Transistors (BJTs). Turn-off time decreases with increases in the recombination rate of minority carriers at switching transients. Fast neutron irradiation on a Si BJT incurs lattice damages owing to the displacement of silicon atoms. The lattice damages increase the recombination rate of injected holes with electrons, and decrease the hole lifetime in the base region of pnp Si BJT. Fast neutrons generated from a beryllium target with 30 MeV protons by an MC-50 cyclotron were irradiated onto pnp Si BJTs in experiment. The experimental results show that the turn-off time, including the storage time and fall time, decreases with increases in fast neutron fluence. Additionally, it is confirmed that the base current increases, and the collector current and base-to-collector current amplification ratio decrease due to fast neutron irradiation.