• Journal of IKEEE
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• v.22 no.4
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• pp.985-991
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• 2018

In this paper, an equivalent circuit reflecting the internal loss of the LLC resonant half bridge converter was proposed and a steady state characteristic equation including the loss factors was derived. Using the results, the frequency characteristics of I/O voltage gain and input impedance were compared with the lossless model In order to verify the proposed model and the derived equation, the main components of the 1kW class LLC resonant half bridge converter were selected under the same conditions and the steady state characteristics such as voltage gain and input impedance were compared. In particular, to compare more closely the steady state error of the two models, we observed the change in switching frequency with respect to the load current, which is considered to be the most important in the actual circuit design stage. As a result, it is confirmed that the error of the operating frequency is significantly improved from the proposed model and the analysis result.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.169-173
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• 2004

This paper presents the basic application idea of superconductor cable for voltage stability limited power system. In bulk power system, the transfer capability of transmission line is often limited by the voltage stability, and superconductor cable could be one of the countermeasure to enhance heat transfer limit as well as voltage stability limit. Steady state voltage stability approach by P-V curve is used to calculate the maximum transfer capability of initial system and superconductor applied system. IEEE-14 bus system is used to demonstrate its applicability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.155-161
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• 2005

Nonlinear electronic loads used at office buildings distort the voltage and current waveform that cause the overheating of transformer losses, ELB(Electrical Leakage Breaker) tripping, and so on. This paper analyzed waveform distortion characteristics at several once buildings by comparing with magnitude of voltage and current harmonics, crest factor of voltage and current, phase voltage and current unbalance. As a consequence, severe current waveform distortion in phase and neutral line by harmonics and high current unbalance rates by unbalanced using of single loads among the three phases are investigated. The results of the study can be used in making decisions regarding reasonable and economical operating of loads at office buildings.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.360-362
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• 2006

기존 플라이백 컨버터의 출력 정류 다이오드는 변압기 누설 인덕터와의 공진으로 소자의 전압 스트레스 부담이 크며 스너버의 부가가 필수적이다. 반면 제안된 다이오드 클램프 정류기를 채용한 플라이백 컨버터는 출력 다이오드가 출력전압의 절반 또는 출력전압으로 클램프 되어 전압 내압을 대폭 줄일 수 있고, 손실이 큰 스너버가 필요 없으며 저가형 및 고효율의 장점이 있다. 본 논문에서는 제안된 컨버터를 소개하고 동작원리 및 동작모드 해석과 시뮬레이션 및 실험을 통한 검증결과를 제시 한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.488-495
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• 2003

In recent years, the multilevel inverter synthesizing the output voltage with step pulse has been widely used rather than PWM method as a solution for high power and high voltage applications. This method takes advantage of lower switching losses due to one switching for one period. This paper proposes a simple method to obtain the conducting angle. This method is implemented by using voltage-second areas of the divided reference voltage according to the output voltage levels. It Is possible to reduce an amount of calculation because it is not required to solve the simultaneous equations by an iterative method. Also, the proposed method can get the conducting angle by means of on-line.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.37-42
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• 2006

The voltage drop in electrical circuits causes a heat accumulation of wiring. This heat could change the specific character of an insulator and deteriorate the dielectric strength so that it could affect an electric leakage, an electric ant a power failure and a fire caused by the short circuit. Therefore optimal design for voltage drop in electrical wiring became an important factor to ensure the safety and economical efficiency of electrical facilities. So in this paper, I analyzed consequences that voltage drop affects in electrical wiring in multi-distributed system used for low electrical system such as road lights, Building, subway station which needs securities for the public society. And I proposed voltage drops computation program and optimal design to ensure the safety and economical efficiency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.1088-1094
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• 2006

In this paper, we establish a mode oxidation process for formation of $Ta_2O_5$ insulator film. The voltage drop in the electrolyte is affected not in voltage change but in current change. If the voltage drop in the electrolyte is same with cathode oxidation voltage, the current changes logarithmically in proportion to the voltage drop in interface of Ta2O5/electrolyte. As a result of the measurement on the electrical property of $Ta_2O_5$ insulator film, when the thickness of the insulator film is $1500\AA$, the breakdown voltage is 350volts Ind dielectric constant is 29.

• Journal of the Korean Electrochemical Society
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• v.10 no.3
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• pp.196-202
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• 2007

The performance characteristics of the polymer electrolyte fuel cells (PEFCS) were investigated under various humidification conditions at steady-state and transient conditions. The PEFC studied in this study was characterized by I-V curves in the potentiostatic mode and EIS (electrochemical impedance spectroscopy). The I-V curves representing steady-state performance were obtained from OCV to 0.25 V, and the dynamic performance responses were obtained at some voltages. The effects of anodic external humidification were measured by varying relative humidity of hydrogen from 20% to 100% while dry air was supplied in the cathode. At the high voltage region, the performance became higher with the increase of the temperature, while at the low voltage region, the performance decreased with the increase of temperature. The EIS showed that ohmic losses were larger at the dry condition of membrane and the effects of mass transport losses increased remarkably when the external and self-humidification were high. The dynamic responses were also monitored by changing the voltage of the PEFC instantly. As the temperature increased, the current reached steady-state earlier. The self-humidification with the generated water delayed the stabilization of the current except for low voltage conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.699-702
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• 2012

본 논문에서는 WCDMA(Wide Code Division Multiple Access) 시스템 사양을 만족시키는 주파수 합성기 블록 중 위상잡음 및 전력소모의 최적 설계가 필요한 LC-VCO(voltage controlled oscillator)의 설계를 제안 하였다. 최적 설계를 위한 핵심내용은 LC-tank의 손실성분을 보상하는 MOS트랜지스터의 전달컨덕턴스와 인덕턴스 평면에 여유이득라인과 튜닝 범위 라인을 그어 설계 가능한 영역 내에서 위상잡음이 최소가 되는 인덕턴스 값을 구하고 선택하는 것이다. 제안한 최적 설계방법에 의해 진행된 LC-VCO의 시뮬레이션 결과 위상잡음 특성은 1MHz옵셋에서 -113dBc/Hz였다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.60-61
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• 2016

본 논문에서는 interleaved 벅-컨버터를 영-전압 스위칭으로 구동하기 위한 새로운 회로를 제안한다. 제안하는 회로는 두개의 벅-컨버터 모듈과 보조 회로로 구성된다. 보조 회로는 coupled-inductor와 커패시터로 구성된다. Coupled-inductor에 흐르는 전류가 스위치가 꺼지기 전에 스위치의 전류의 방향을 바꾸어서 영 전압 스위칭을 달성한다. 제안하는 회로는 보조회로에 반도체 소자를 추가하지 않고 수동 소자만으로 구성하여 신뢰성의 저하를 막는다. 또한 수동 소자만으로 구성된 보조 회로로 인해 발생하는 도통 손실의 증가를 최소화 한다. 제안하는 회로는 시뮬레이션을 통해 검증하였다.