• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.242-243
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• 2010

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torch. Series resonant half-bridge topology is presented to be a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. The plasma torch rated for 3MW, 2kA and having the physical size of 1m long is selected to be a high enthalpy source in waste disposal system. The steady-state and transient operations of plasma torch are simulated. The parameters of Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. Circuit simulation waveform shows that the ripple of arc current can be maintained within ${\pm}10%$ of its rated value under the existence of load disturbance. This power conversion configuration provides high enough ignition voltage around 5KA during ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.159-160
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• 2012

For renewable energy has been studied by many research. among them, non-pollution and infinite solar energy using solar power system is newly spotlighed. the DC output characteristic of the solar cell, connection to grid and using the inverter is essential to the process of converter DC to AC. in this paper, study the corresponding changes in the efficiency of the inverter and arcing occurs in the inverter, depending on the conditions and regulations in the UL-1699 series arc occurs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.147-152
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• 2012

This paper dealt with the frequency component analysis of acoustic signals produced by corona and series-arc discharges as a diagnostic technique for closed-switchboards. Corona and series-arc discharge were simulated by a needle-plane electrode and an arc generator specified in UL1699, respectively. Acoustic signal was detected by a wideband acoustic sensor with a frequency bandwidth of 4 Hz~100 kHz (-3 dB). We analyzed frequency spectrums of the acoustic signals detected in various discharge conditions. The results showed that acoustic signals mainly exist in ranges from 30 kHz to 60 kHz. From the experimental results, an acoustic detection system which consists of a constant current power supply (CCP), a low noise amplifier (LNA) and a band pass filter was designed and fabricated. The CCP separates the signal component from the DC source of acoustic sensor, and the LNA has a gain of 40 dB in ranges of 280 Hz~320 kHz. The high and the low cut-off frequency are 30 kHz and 60 kHz, respectively. We could detect corona and series-arc discharges without any interference by the acoustic detection system, and the best frequency is considered in ranges of 30 kHz~60 kHz.

• Journal of Power Electronics
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• v.11 no.4
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• pp.591-598
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• 2011

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3MW, 2kA and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ${\pm}10%$ of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.427-428
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• 2015

본 논문은 DC 배전시스템 내에서 발생할 수 있는 직렬 DC 아크 고장을 검출하기 위한 알고리즘을 제안한다. 직렬 DC 아크 고장은 동일 전위의 도선 또는 접속점의 노화 등으로 인해 발생하며, 아크 고장 에너지의 크기에 따라 수초 이내에 화재 사고를 유발할 수 있기 때문에 정확한 고장 검출을 통한 빠른 제거가 필요하다. 스위칭 전력변환 장치에서 발생하는 노이즈 성분에 의한 검출 알고리즘의 오동작 현상을 제거하기 위해 시간 영역에서의 전류 변화와 주파수 영역에서의 전류 크기 차이를 동시에 이용하여 직렬 DC 아크 고장 발생여부를 검출하게 된다. 제안 알고리즘은 5kW급 용량의 380V 저전압 DC 배전 시스템을 대상으로 검증하였다.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.137-139
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• 2003

Micro-Sources arc emerging as a providing environmentally friendly and reliable and effective solution. Micro-Source converter DC voltage of prime mover to AC voltage using voltage source inverter for interjecting with AC grid system. This paper studies optimal series inductance size for interjecting with AC grid system.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.385-388
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• 1994

This paper presents a new configure rectifier which has improved input power factor and efficiency for DC arc weldings. Two rectifiers are series connected and they are single-phase full-wave phase controlled rectifiers that use a transformer with two center-tapped secondary. The input power factor can be improved by controlling the each phase of rectifiers sequentially, and then the efficiency can be also improved because the reactive component currents will be reduced. It is confirmed that the proposed rectifiers has about 80% of input power factor and efficiency with the experimental results which are carried out at the output ranges of 100A to 300A.

• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.216-220
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• 1996

In the present paper, a new type of DC arc plasma torch is disclosed. The principles of the new magnetic and fluid dynamic controlled large orifice long discharge tunnel plasma torch is discussed. Two series of DC Plasma Jet diamond film deposition equipment have been developed. The 20kW Jet equipped with a $\Phi$70 mm orifice torch is capable of deposition diamond films at a growth rate as high as 40$\mu\textrm{m}$/h over a substrate area of $\Phi$65 mm. The 100kW high power Jet which is newly developed based on the experience of the low power model is equipped with a $\Phi$120 mm orifice torch, and is capable of depositing diamond films over a substrate area of $\Phi$110 mm at growth rate as high as 40 $\mu\textrm{m}$/h, and can be operated at gas recycling mode, which allows 95% of the gases be recycled. It is demonstrated that the new type DC plasma torch can be easily scaled up to even higher power Jet. It is estimated that even by the 100kW Jet, the cost for tool grade diamond films can be as low as less than ＄4/carat.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.43-46
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• 2007

In this paper, a novel new pulse power generator based on IGBT stacks is proposed for pulse power application. Proposed scheme consists of series connected 9 power stages to generate maximum 60kV output pulse and one series resonant power inverter to charge DC capacitor voltage. Each power stages are configured as 8 series connected power cells and each power cell generates up to 850VDC pulse. Finally pulse output voltage is applied using total 72 series connected IGBTs. The synchronization of gating signal is important for series operation of IGBTs. For gating signal synchronization, full bridge inverter and pulse transformer generates on-off signals of IGBT gating and specially designed gate power circuit was used. Proposed scheme has lots of advantages such as long lifecyle, compact size, flat topped pulse forming, small weight, protection for arc, high efficiency and flexibility to generate various kinds of pulse output.