• 전기학회논문지
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• 제64권1호
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• pp.23-28
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• 2015

Two old synchronous condensers in Jeju are being replaced by new machines to operate Jeju AC network with Haenam-Jeju HVDC system stably. Before new synchronous condensers operate on site, voltage stability analysis is conducted to verify stable operation of jeju AC network. Through impedance analysis of the synchronous machine, transformer and ac network, the equivalent circuit is constructed and the voltage drop during start-up is calculated. Then, PSS/E fault analysis is performed to acquire short-circuit capacity according to the generator operation scenarios. Voltage variation when starting synchronous condenser is simulated in PSCAD/EMTDC and satisfies the operating condition of jeju AC network and HVDC #1 system.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.94-98
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• 2002

The Partial breakdown (PBD) and complete breakdown (BD) voltage characteristics in a composite insulation system of glass fiber reinforced plastics (GFRP) and liquid nitrogen are investigated to find the PBB and BD characteristics in solenoid type high temperature superconducting (HTS) coils at quench. The electrode system used is made from a coaxial spiral coil-to-cylindrical electrode with an insulation barrier and spacers, and is immersed in liquid nitrogen. A heater is mounted inside the coil electrode to generate boiling which occurs on quenched superconducting coils. The experimental results show that: (1) breakdown voltages are affected severely by the risetime of the applied voltage and the PBD inception voltage, (2) two kinds of BD mechanisms are found depending on the shape of the spacer, length of cooling channel and heater power.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.456-458
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• 1997

The phase-lock technique is applied to a three-phase semi-bridge type battery charger system. Using an inner fast dynamic loop, the phase-locked voltage control (PLVC) technique of three-phase semi-bridge converter is proposed to give a frequency synchronism and to reduce the subharmonics due to the unbalance of transformer or power line. To protect the power devices, the two stage soft-start, function with softly locking the phase and softly increasing the current is presented. As limiting the reference voltage of the inner voltage control loop, muti-lock phenomena are removed on the PLVC loop. A current limit function is also proposed to limit the current of battery and converter. The proposed controller is confirmed through experiment results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.193-194
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• 2008

IEC 61850 기반의 변전소자동화시스템이 세계적으로 많은 관심을 가지면서 IEC 61850 프로토콜 기반의 IED(Intelligent Electronic Device) 개발을 위해 전 세계적으로 많은 노력이 진행되고 있다. 본 연구에서는 IEC 61850 표준규격에서 제안하는 객체 모델링 및 통신프로토콜을 이용하여 2권선 변압기 보호용 IED를 개발하고 그 구현방법을 설명하였다. 구현을 위해 리눅스 OS(Operation System)가 포팅된 통신보드에 MMS(Manufacturing Message Specification), GOOSE(Generic object oriented substation event) 통신모듈을 탑재하였고 데모 시스템을 구성하여 성능을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2301-2302
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• 2008

We experimentally investigated discharge phenomena inside vacuum interrupter at 1 to 20 Torr to simulate the vacuum leakage. We used glass type of vacuum interrupter where the internal pressure and the type of gasses can be varied according to requirement. The experiment is conducted under ac applied voltage and the experimental circuit is constructed to simulate the actual circuit used in cubical type insulated switchgear. We used two types of gases such as air and SF6. The use of glass type vacuum interrupter allowed us to measure discharges occurring in vacuum interrupter optically. We measured and discussed the discharge occurring in both gases with a current transformer and ICCD camera. We also revealed that electromagnetic wave spectra emitted by the discharge have same frequency range for both gasses.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.419-422
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• 2008

This paper presents a novel prototype of ZCS-PFM high frequency series resonant Inverter using IGBT power module for electromagnetic induction eddy current-heated roller in copy and printing machines. The operating principle and unique features of this voltage source half bridge inverter with two additional soft commutation inductor snubber are presented Including the transformer modeling of induction heated rolling drum. This soft switching inverter can achieve stable zero current soft commutation under a discontinuous and continuous resonant load current for a widely specified power regulation processing. The experimental results and computer-aided analysis of this inverter are discussed from a practical point of view.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.368-371
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• 2008

An extensometer system to measure strain and displacement of cylindrical fatigue specimen in a autoclave of high temperature and high pressure environment has been developed by KEPRI. The extensometer reads the displacement caused by fatigue loads at the target length of the specimen installed inside the autoclave. The performance of the extensometer were tested at 15MPa, $315^{\circ}C$ of a operating pressurized water reactor. Two LVDT's of magnet type were connected to the extensometer and used for converting the fatigue displacement to electronic signal. The device is being used for developing environmental fatigue curve of CF8M cast austenitic stainless steel (CASS) in the test condition of low cycle and low strain. This paper introduces the background and results of the development.

• 한국군사과학기술학회지
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• 제9권1호
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• pp.89-98
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• 2006

This paper describes signal attenuation characteristics as splicing the output on LVDT for stability and reliability of switching mechanism, which is developed to use common signal between FLCC and EDFLCC, on T-50 aircraft. The method of test is classified a Pspice simulation and an actual hardware evaluation. The difference of error margin for two methods is 10times, the latter higher. The result in this experiment shows that the signal attenuation as splicing the output on LVDT doesn't affect and the static error margin is 53% for develope the EDFLCC.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.134-137
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• 1998

In this paper, a hybrid maximum power tracker for a photovoltaic/wind hybrid power system is proposed. In the hybrid system, a direct interfacing the wind power system to the photovoltaic system gives the problems of voltage fluctuations, poor maximum power tracking, and harmonics generation associated with the random wind speed, the random solar irradiation and the pulsating torque came from the wind turbine synchronous generator and photovoltaic. To overcome these problems, a wind side DC/DC converter are proposed employing a star/delta transformer interconnected between the wind turbine side and the photovoltaic side. The control objective for each dc/dc converter is to extract maximum power from each different photovoltaic system and wind system, and transfer two different powers to the inverter and load.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.39-42
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• 2006

a current stress reduction technique for a boost integrated half-bridge (BIHB) DC/DC converter with voltage doubler type rectifier is proposed for digital car audio amplifier application. In the proposed circuit, two external capacitors are added parallel to the rectifier diodes in the secondary side of the transformer to shape the primary and the secondary current like rectangular waveforms in every switching instance. The experimental results of a 200W industrial sample show that the peak primary current decreases about by 10A. Thus, the proposed technique shows improved high efficiency.