• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.207-210
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• 2004

In oil-filled equipment such as transformers, partial discharge or local overheating will make insulating material(oil, kraft paper, proclain and wood) be stressed and generate many sort of gases($CO,\;CO_2,\;H_2,\;C_2H_4$) which are dissolved in transformer oil. The ratio of this gas can make diagnostic tecchniques of the lifetime of transfomer so, it is important to monitoring $H_2$ gas continuously. This paper developes a system of detecting about $H_2$ gas by using $H_2$ gas sensor, and we describe operation and performance of this system

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1842-1844
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• 2004

In oil-filled equipment such as transformers, partial discharge or local overheating will make insulating material(oil, kraft paper, proclain and wood) be stressed and generate many sort of gases(CO, $CO_2,\;H_2,\;C_2H_4$) which are dissolved in transformer oil. The ratio of this gas can make diagnostic tecchniques of the lifetime of transfomer so, it is important to monitoring $H_2$ gas continuously. This paper developes a system of detecting about $H_2$ gas by using $H_2$ gas sensor, and we describe operation and performance of this system.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.55-58
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• 1992

Due to the fault signal containing high and/or slowly decaying dc off-set component, saturation of current transformers cause errors in reproducing secondary current and therefore, secondary current is distorted, which cause relay to maloperate. In this paper, a new method which determines whether current transfomer is saturated is proposed. By designing digital filter of current transfomer, although secondary is distorted, exact secondary current can be reproduced.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.24-31
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• 1992

A 24 pulse current source inverter for reducing the harmonics in output currents is presented in this paper. The proposed system operates a 24 pulse inverter by adding only tap changing circuit which consists of several taps and static switching elements to the 12 pulse inverter, which is the double connected 3 phase 6 pulse inverter with an auto transfomer. Also to optimize the effectiveness of the harmonic reduction, the optimum turn ratio and tap changing control angle of auto transfomer are decided by digital simulation and its validity is verified with experiment. And under the optimum condition, it is clarified that the harmonics components involved in the output current of the proposed inverter are nearly equal to those of the conventional 24 pulse inverter.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1511-1514
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• 2002

This paper presents design and construct of flat type step-down piezoelectric transformer for the application to AC adaptor. This piezoelectric transformer operated in resonance vibration mode. In this paper, finite element method(FEM) was used for analysing piezoelectric transformers. Stress and electric field of the transformer were simulated at resonance frequency. Using this simulation results, we manufactured improved Rosen type piezoelecric transfomer and measured its output characteristics. As results, output power was linearly increased by increasing input power at resonance frequency and it was found that the transformer an invariable output power for input power. From these results, we expect that this piezoelecric transfomer can be applied to small size and low capacitive AC adaptor.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.111-115
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• 1997

This Paper is concerned on developing DC-DC converter using ZVS-FB-PWM Converter. The converter output is 28V and regulated by phase shift control methode. MOSFET is used by the main switching device and high frequency transfomer is made for operating at 300㎑ switching frequency. When the load vary widely, converter's ZVS characteristic is expressed by experiment result.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.289-290
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• 2011

일반적으로 사용되는 변압기에 비해 공진형 컨버터의 변압기와 유도급전 시스템에 사용되는 비접촉 변압기의 경우 공극이 아주 크다. 이런 경우, 일반적인 측정 방법으로는 정확한 변압기의 변수를 얻을 수 없다. 하지만 coupled 인덕터 측정 방법을 이용하여 공극이 큰 변압기의 변수를 측정하면 일반적인 변압기 측정 방법에 비해 정확한 변압기 변수를 얻을 수 있다. 그러므로 본 논문에서는 공진탱크를 구현하여 PSpice 시뮬레이션과 임피던스 분석기(PSM1735)의 결과를 비교하여 2가지 측정 방법 중 coupled 인덕터 측정 방법이 정확하게 측정 가능함을 검증하였다.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.257-260
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• 2002

In this paper, the circuit of AC Choppers for $CO_2$laser Power Supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transfomer used with the proposed system. This improved circuit employs a 3 electrode-type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirment, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$: $N_2$: He = 1 : 9 : 15, total pressure of 15torr.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1488-1489
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• 2015

본 논문에서는 154kV 주변압기 3차측에서 사용하고 있는 6~10kV급 전력케이블인 TFR-CV $400mm^2$의 절연파괴고장에 대한 원인을 분석하였다. 대상 케이블은 2010년 9월에 가압하여 약 4.4년 운전 후 발생하였으며 차폐부 제거 후 열수축튜브를 시공한 사례이다. 위와 같이 차폐부를 제거한 케이블의 고장분석사례를 소개하고 고장 재발방지방안을 제안하고자 한다. 이 논문은 향후 변압기 신 증설 및 교체, 운영에 활용할 수 있을 것으로 사료된다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.3
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• pp.432-437
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• 1996

This paper describes a diagnostic technique of power transformers by on-line detection of ultrasonic signals. A trend of partial discharge variation in a real transformer was estimated by counting the number of ultrasonic signals until insulation paper in the point-to-plane electrode is punctured. The number of electrical signals is closely related to the ultrasonic signals generated by partial discharge. The trend of the ultrasonic signal number could easily be distinguished by taking moving average. The insulation failure due to partial discharge in transformers can be predicted based on the trend analysis of ultrasonic signal number caused by partial discharge. (author). 14 refs., 10 figs.