• International Journal of Safety
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• 제5권1호
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• pp.29-32
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• 2006

There has been an increasing need for substitute energy development due to the dry up of the fossil fuel and environmental problems. Among the substitute energy under consideration, producing hydrogen from water without the accompanying release of carbon has become a promising technology. Also, Iodine-Sulfur (IS) thermochemical water decomposition is one of the promising processes that can produce hydrogen efficiently using the high temperature gas-cooled reactor (HTGR) as an energy source capable of supplying heat at over 1000. In this study, to effect an initiating events identification of the IS process, Master Logic Diagram (MLD) was used and 9 initiating events that cause a leakage of the chemical material were identified.

• 전력전자학회논문지
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• 제11권6호
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• pp.529-534
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• 2006

요즘 많은 연구자들이 전력변환회로의 효율을 올리는데 이전보다 훨씬 많은 관심을 기울이고 있다. 플라이백 컨버터에서 RCD 스너버의 저항은 누설인덕터에 저장된 에너지를 소모한다. 이는 전체 시스템 효율을 감소시키는 역할을 한다. 그래서 이 논문에서는 효율을 향상시키기 위해서 플라이백 컨버터의 새로운 에너지 회복회로를 제안한다. 제안된 회로의 동작원리를 자세히 설명한다. 그리고 이를 모의실험 및 실험을 통해서 확인한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.106-109
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• 2000

There have been proposed two types of low bit rate vocoder upto now : One is MBE type using the spectrum modeling and another is CELP type using the hybrid coding method. CELP type vocoder has mainly studied between them. Specially, much of intensity is concentrated in CELP vocoder due to the emergence of Internet Phone and PCS in a domestic. In order to improve the speech quality in CELP vocoder, in this paper, we proposed a new spectrum analysis algorithm with variable window, In CELP vocoder, the spectrum of the synthesised speech signal is distorted because the fixed size windows is used for spectrum analysis. So we have measured the spectral leakage and in order to minimize the spectral leakage have adjusted the window size. Applying this method G.723.1 ACELP, we can get SD(Spectral Distortion) reduction 0.084(dB), residual energy reduction 6.3% and MOS(Mean Opinion Score) improvement 0.1.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 추계종합학술대회
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• pp.581-584
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• 2000

This paper describes the effect of lightning impulse current on ZnO varistors(390 V, 6.5 kA) used in low-voltage AC mains as a protective device against transient overvoltages. A lightning impulse current standardized in IEC 61000-4-5 is applied to the varistors, and the energy applied to the varistor at each time is about 12 J. In the experiment, various Parameters such as leakage current, reference voltage are measured with the number of applied impulse current. Also, micro-structure changes of the varistors after applying the lightning impulse current of 200 times are compared. The electrical characteristics of the varistors are degraded by overtime impulse current, showing increase in leakage current and decrease in reference voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.289-292
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• 1997

BaTiO$_3$thin film capacitor were prepared on Pt(100)/SiO$_2$/Si(100)wafer by RF sputtering technique. Dielectric and electrical characteristics of the thin film capacitor are investigated. The Dielectric constant and loss were about 683 and 5[%], respectively. We found that the leakage current of thin film capacitor is depend on RF power during deposition. Because of increase of activation energy, leakage current inclosed at high RF power and sheet resistivity of the films was decreased. Swithching voltage of thin film capacitor was 4.4[V]

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.907-909
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• 1998

This paper describes the effect of impulse current on degradation of ZnO blocks. In this study, an impulse current generator which can produce 8/20 [${\mu}s$], 3 [kA] and 4/10 [${\mu}s$], 5 [kA] waveform is designed and fabricated to simulate the lightning impulse current. The residual voltage, reference voltage, and leakage current flowing to the ZnO blocks are observed. The experimental results show that the leakage current increases continuously with the number of applied impulse current, but no significant changes in residual voltage and in operating voltage are observed until the ZnO block is destroyed. Also, it is confirmed that the main factor on degradation of ZnO blocks is rather the total energy applied to ZnO blocks than the peak value of the impulse current.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1393-1395
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• 2004

Arresters are the best protective device on electrical power systems against transient overvoltages generated by lightning and/or switching operation. Nonetheless, arresters will be deteriorated due to absorption of moisture in the environments of its use, repetition in the protective operation to overvoltages, and some defects at manufacturing. It is therefore important to estimate the electrical characteristic changes of ZnO blocks. In this paper, an accelerated deterioration test by a standard lightning impulse current was carried out to extract parameters needed for diagnosing arrester deterioration, and leakage current components were measured. Total energy applied to the ZnO blocks at each time is 1,050[J] in 8/20[${\mu}s$] impulse current. From the experimental results, we proposed electrical parameters and leakage current level to diagnose arrester soundness.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.59-62
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• 2007

연료전지는 수소를 이용하여 전기를 생산하는 발전 시스템으로 운전 중 수소 누출과 폭발의 위험성을 항상 수반하고 있다. 따라서 안전성의 확보를 위해 연료전지 시스템 내부에서 수소 누출 시 유e동 특성으로 인한 특정 부근 농도 정체와 환기의 영향을 파악하는 것이 필요하다. 실험 장치와 전산유체역학 프로그램을 사용하여 챔버 내 수소의 유통 특성과 환기구에 따른 환기의 영향을 확인하였다. 수소의 누출 속도와 양에 따라 유동장의 형태는 크게 변하였으며 환기구의 위치와 크기는 특정 부근의 농도정체와 챔버 내 전체적인 수소 농도에 영향을 미침으로서 안정성을 확보하는 중요한 인자임을 알 수 있었다. 예측 결과를 실제 실험 모델과 비교하여 그 타당성을 검토하였으며 차후 가정용 연료전지 모듈의 환기구 설계에 적용할 수 있다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.139.1-139.1
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• 2011

Electric vehicle use independent electricity of high voltage. if isolation of electricity is destructed, devices and people are considerably damaged. Therefore, detection of ground fault is necessary for electric vehicle. As the existing detection method of ground fault can not detect ground fault when isolation of both positive side and negative side of electricity is destructed, and change of voltage of electricity. This paper proposed detection method for ground fault of both two sides of electricity and change of voltage. The proposed method is verified by analysis of equivalent circuit.

• Journal of Power Electronics
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• 제11권6호
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• pp.779-786
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• 2011

This paper presents a soft switching converter to achieve the functions of zero voltage switching (ZVS) turn-on for the power switches and dc voltage step-up. Two circuit modules are connected in parallel in order to achieve load current sharing and to reduce the size of the transformer core. An active snubber is connected between two transformers in order to absorb the energy stored in the leakage and magnetizing inductances and to limit the voltage stresses across the switches. During the commutation stage of the two complementary switches, the output capacitance of the two switches and the leakage inductance of the transformers are resonant. Thus, the power switches can be turned on under ZVS. No output filter inductor is used in the proposed converter and the voltage stresses of the output diodes is clamped to the output voltage. The circuit configuration, the operation principles and the design considerations are presented. Finally, laboratory experiments with a 340W prototype, verifying the effectiveness of the proposed converter, are described.