• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.159-167
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• 1999

This paper presents a new transient voltage blocking device(TOBD)which low power and high frequency bandwidth to protect info-communication facilities from transient voltages. Conventional protection devices have some problems such as low frequency bandwidth low ener-gy capacity and high remnant voltage. in order to improve these limitations a hybrid type TOBD which consists of a gas tube avalanche diodes and junction type field effect transistor (JFETs) is developed. The TOBD differs from the conventional protection devices in configuration and JFETs are used as an active non-linear element and a high speed switching diode with low capacitance limited high current. Therefore the avalanche diode with low energy capacity are protected from the high current and the TOBD has a very small input capacitance. From the performance test using combination surge generator which can produce $1.2/50{\mu}m$ 4.2 kV/max, $8/20{\mu}m$ 2.1 kAmax it is confirmed that the proposed TOBD has an excellent protection per-formance in tight clamping voltage and limiting current characteristics.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.622-625
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• 1999

This paper introduces a novel zero-voltage switching (ZVS)) pulse width modulation (PWM) active clamping dc-to-dc boost converter. This technique presents ZVS commutation without additional voltage stress and a significant increase in the circulating reactive energy throughout the converter. Therefore, all of the losses for the switches are minimized, and high power density system can be realized. The characteristics are verified through simulation and experimental results.

• 대한전기학회논문지
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• 제38권4호
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• pp.269-278
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• 1989

When the induction motor is operated by CSI, the commutation capacitance in the CSI circuit is increased according to the increase of large capacitor system. The output voltage spikes are generated at the moment of charge and discharge of the commutation capacitor. Also, since output current comprise a great number of harmonics, torque ripples of the motor are generated, having bad effects on the motor. In this study, by adopting the 18-phase multiple high Frequency Current Source Inverter (HFCSI), torque ripples generated by the voltage spikes are mostly eliminated except the 17th and 19th harmonics. To reduce the voltage spikes comprised in the output voltage, particularly, the methods of eliminating the cause of bad effect upon the motor are proposed in this paper. In the proposed method, by using additional voltage Clamping Curcuit (VCC), it is possible to select the values of commutation capacitor energy loss in commutating, the commutating capacitor, and the capacitor in the clamping circuit.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.164-168
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• 2004

A Zero-Voltage-Switching(ZVS) Three-Level Converter realizes ZVS for the switches with the use of the leakage inductance(or external resonant inductance) and the output capacitors of the switches, however; the rectifier diodes suffer from recovery which results in oscillation and voltage spike. In order to solve this problem, this paper proposes a novel ZVS Three-Level converter, which introduces two clamping diodes to the basic Three-Level converter to eliminate the oscillation and clamp the rectified voltage to the reflected input voltage.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.279-281
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• 1996

This paper deals with the two stage surge protection device by using varistor and LC low pass filter. Recently varistor alone has been used with overvoltage protection devices for the AC power mains and has same problems associated with high remnant voltage and noise. In this work, in order to improve the cutoff performance of surge protection device, the lightning surge protection device having two stage hybrid circuit for an AC single phase mains was designed and fabricated. Operation characteristics and surge clamping performance of the surge protection device in an $8/20{\mu}s$ surge current are investigated. As a consequence, it is found that the proposed two stage surge protective device for AC power mains has a variety of advantages such as a smaller clamping voltage, high frequency noise reduction and large clamping capacity.

• Journal of Power Electronics
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• 제18권2호
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• pp.395-406
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• 2018

Marine controlled-source electromagnetic transmitters (MCSETs) are important in marine electromagnetic exploration systems. They play a crucial role in the exploration of solid mineral resources, marine oil, and gas and in marine engineering evaluation. A DC-DC controlled-source circuit is typically used in traditional MCSETs, but using this circuit in MCSETs causes several problems, such as large voltage ringing of the high-frequency diode, heating of the insulated-gate bipolar transistor (IGBT) module, high temperature of the high-frequency transformer, loss of the duty cycle, and low transmission efficiency of the controlled-source circuit. This paper presents a clamping-diode circuit for MCSET (CDC-MCSET). Clamping diodes are added to the controlled-source circuit to reduce the loss of the duty ratio and the voltage peak of the high-frequency diode. The temperature of the high-frequency diode, IGBT module, and transformer is decreased, and the service life of these devices is prolonged. The power transmission efficiency of the controlled-source circuit is also improved. Saber simulation and a 20 KW MCSET are used to verify the correctness and effectiveness of the proposed CDC-MCSET.

• 조명전기설비학회논문지
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• 제29권1호
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• pp.94-102
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• 2015

The electronic ballast for HID lamps needs to ignite lamps even though the length from the ballast to lamp is far away. Therefore, it needs to do the research on a resonant ignition to turn on the HID lamps because the reduction of ignition voltage is not much depending on the distance. However, the parasitic capacitance is increased depending the length of the cable, and it affects the resonant frequency. The ignitor voltage can be increased drastically under the resonant ignition through frequency sweep, and it is the main reason of blowing up. Therefore, the clamping diode is proposed to suppress the voltage of the primary winding during resonant ignition.

• Journal of Power Electronics
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• 제10권3호
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• pp.235-244
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• 2010

This paper presents a new isolated soft-switching bidirectional buck-boost inverter for fuel cell applications. The buck-boost inverter combines an isolated DC-DC converter with a conventional inverter to implement buck-boost DC-DC and DC-AC conversion. The main switches achieve zero voltage switching and zero current switching by using a novel synchronous switching SVPWM and the volume of the transformer in the forward and fly-back mode is also minimized. This inverter is suitable for wide input voltage applications due to its high efficiency under all conditions. An active clamping circuit reduces the switch's spike voltage and regenerates the energy stored in the leakage inductance of the transformer; therefore, the overall efficiency is improved. This paper presents the operating principle, a theoretical analysis and design guidelines. Simulation and experimental results have validated the characteristics of the buck-boost inverter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2628-2631
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• 1999

One of the limitations of conventional ASCI for high-power induction motor drives is the high voltage that is produced in the commutation capacitors during the current commutation from one phase to another. Since the capacitor voltage appears directly on the semiconductor components, it increases their required voltage ratings. Also, the high-voltage spikes generated at the motor terminals may cause damage to the motor insulation. And we investigated how de input power is increased or decreased according to size of de link inductor. In this paper, de link inductor and clamping capacitor in GTO inverter suitable for induction motor drives are propose through experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.124-126
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• 1988

The induction motor is constantly operated by general source, thus its speed control is employed an inverter system which can convert DC into AC. The CSI(Current Source Inverter) which have a commutation capacitor in its circuit is liable to cause a voltage spike that it is due to charge and discharge of commutation capacitor. And six phases inverter makes a number of harmonics. These have a effect upon the induction motor badly. This paper aims to suggest a way to reduce such adverse effects by maximally cutting the voltage spike as well as by eliminating a number of harmonics through the operation of Multi-HFCSI.