• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.7
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• pp.28-36
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• 2008

This paper presents a novel prototype of zero current switching pulse frequency modulation (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-fed 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.

• Journal of Power Electronics
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• v.9 no.3
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• pp.472-480
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• 2009

In this paper, a charge equalization converter with parallel-connected primary windings of transformers is proposed. The proposed work effectively balances the voltage among Lithium-Ion battery cells despite each battery cell has low voltage gap compared with its state of charge (SOC). The principle of the proposed work is that the equalizing energy from all battery strings moves to the lowest voltage battery through the isolated dc/dc converter controlled by the corresponding solid state relay switch. For this research a prototype of four Lithium-Ion battery cells is optimally designed and implemented, and experimental results show that the proposed method has excellent cell balancing performance.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.177-179
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• 2008

최근 전원부의 소형화 경향에 따라 에너지 변환 소자인 변압기의 소형 경량화 요구가 가속화 되고 있다. 전원부의 고효율 소형화를 위해서 평면 변압기가 대두되고 있다. 이에 따라 본 논문에서는 8[W]급 플라이-백(Flyback) 평면 변압기의 PCB(Printed Circuit Board) 패턴을 FERROXCUBE 사의 평면 변압기 설계 방법을 따라 개념 설계를 하였다. 120[kHz]의 스위칭 주파수에서 동작하는 평면 변압기의 자계 분포(magnetic intensity), 와전류(eddy current), 전계 분포(electric intensity)를 유한 요소법(Finite Element Method)을 이용하여 분석하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.259-262
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• 1998

PbTi $O_3$ family ceramics can be used for the piezoelectric transformer using thickness extensional vibration mode because it is a material with the large anisotropy between electromechanical coupling factors $k_{t}$ and $k_{p}$. However, PbTi $O_3$ family ceramics have a difficult poling condition on account of its large anisotrophy. In this study, the structural and piezoelectric properties of (P $b_{0.76}$ $Ca_{0.24}$)[ $Ti_{0.96}$(M $n_{1}$3/S $b_{2/3}$)$_{0.04}$] $O_3$ system ceramics were investigated as a function of poling voltage in order to find the best poling condition.ion.n.n.ion.n.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1226-1228
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• 2001

In this paper, the modified simulation algorithms of the Auto Transformer (AT) feeding electric train were proposed. To obtain terminal voltage of train by using equivalent circuit of the AT feeding system, the iterative method is proposed for which determine the train voltages. The train voltages are iteratively calculated from the system voltage drop and line impedance. In the case study, the proposed method is verified from actual operation data of the Kwa-Chon line. Also it is verified that the proposed method can be extent to the multi-train simulation tool. The terminal voltage of the multi-train can be calculated by using superposition principle and it is easily applied to the proposed method. Therefore, the proposed method can be a solution for the complexity of the circuit analysis in the existing methods.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.461-463
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• 2000

As increasing the accident of distribution transformers, we need to manage them efficiently. This paper proposes the method for transformer's management using multi-channel wireless data communication. The Data Acquisition System(DAS) was developed to manage transformers and the HDLC protocol applied to the system. Additionally, it will be feasible to diagnose distribution transformers by checking load conditions such as hot spot temperature, ambient temperature, load current, etc. and using adequate algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.43-46
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• 2001

The DC dielectric breakdown of epoxy composites used for transformer was experimented and then its data were simulated by Weibull distribution equation in this study. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it was believed that the adding filler formed interface, charges were accumulated in it, the molecular mobility was raised, the electric field was concentrated, electrons were accelerated and then electron avalanche was early accomplished. From the analysis of Wei bull distribution equation, it was confirmed that as the allowed breakdown probability was· given by 0.1[%], the value of 'applied field was needed to be under 17.20[kV/mm].

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.700-702
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• 2005

The most electrical apparatus should be able to withstand short-time current and peak current during a specified short time until circuit breakers have interrupted fault current. It defines the short-time withstand ability of electric a apparatus to be remain for a time interval under high fault current conditions. It is specified by both dynamic ability and thermal capability. KERI(Korea Electrotechlology Research Institute) recently constructed the new short-time current and low voltage short circuit testing facilities. This paper shows short- circuit calculation of transformer and describes high current measuring system, and evaluate the result of short-time withstand test used in $3{\phi}$ 90MVA short-time current testing facilities.

• 전기의세계
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• v.29 no.5
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• pp.315-320
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• 1980

It has been appeared and widely used today SF6 Gas Insulated Substation(Hereafter called GIS) for the power supply to the densely populated area due to the superior insulation withstand ability of SF6 Gas. And to maximize the compact effect of this substation, it is normal practice to connect underground cables. If it is possible to elieminate the redundant lightning arresters using the physical characterestics of travelling waves in underground cables, economical advantages can be obtained together with easy maintenances. It is presented in this paper the possiblity of eliminating the transformer protection lightning arresters under some conditions for the 154kV GIS's (BIL:750kV) which Korea Electric Co. plans to construct using the general purpose digital computer program.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.4
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• pp.174-179
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• 2002

In this paper, the modified simulation algorithms of the Auto Transformer (AT) feeding electric train system were proposed. To obtain terminal voltage of train by using equivalent circuit or the AT feeding system, the iterative method is proposed for which determine the train voltages. The train voltages are iteratively calculated from the system voltage drop and line impedance. In the carte study, the proposed method is verified from actual operation data of the Kwa-Chon line. Also it is verified that the proposed method can be extent to the multi-train simulation tool. The terminal voltage of the multi-train can be calculated by using superposition principle and it is easily applied to the proposed method. Therefore, the proposed method can be a solution for the complexity of the circuit analysis in the existing methods.