• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.589-594
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• 1998

Heat and fluid flow in the motor block room of a motorized car is numerically simulated. The motorized car, composed of a motor block room and a passenger room, supplies additional Power to achieve the design speed. A motor block, a transformer, and a fan are equipped in the motor block room. Flow phenomena in the ducts on the motor block and power transformer are investigated. Also, the three dimensional heat and fluid flow in the motor block room is simulated to give a qualitative information of the flow characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.156-158
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• 1994

The analysis of the thin lamination model of the amorphous transformer by FEM requires many region, divisions and much calculating tine, and it has difficulty in calculating for mordern computer. A new method which is simulated by a solid but anisotropic block with the magnetic permeabilities in two orthogonal directions selected to account for the presence of the laminations. [1] Based on this equivalent anisotropic block model, we analyzed the iron loss of the amorphous transformer by FEM, and presented an optimal design example of core dimensions for minimizing the iron loss.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.21-23
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• 1995

The analysis of the thin lamination model of the wound core type transformer by FEM requires many region division and much calculationg time, and it has difficulty in calculation by modem computer. A new method which is simulated by a solid but anisotropic block with the magnetic permeabilities in the orthogonal dimension, is selected to account for the presence of the lamination.[1] Based on this equivalent anisotropic block model, we analyze the iron loss of the wound core type transformer by FEM, and compare the simulation results with the experimental results.

• 한국전자파학회지:전자파기술
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• 제2권2호
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• pp.3-10
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• 1991

GaAs FET초고주파 증폭기의 DC 블럭용으로 사용되는 칩 커페시터 대신 DC블럭 및 임피던스 변환 성질을 가진 DC block/transformer(비대칭 2선 마이크로스트립 선로 및 까지낀 3선 마이크로스트립 선로)를 사용한 초고주파 증폭기의 새로운 구성 방법을 제시하였다. 새로운 구성을 갖는 초고주파 증폭기의 대역 특성은 평탄하며 대역폭이 3.5(BHz)인 광대역 특성을 얻으 수 있었다. 초고주파 증폭기에 사용된 깍지낀 3선 마이크로스트리 결합 선로는 DC블럭 기능과 함께 임피던스 정합 역할을 할 수 있는 큰 장점을 가지고 있다.

• 전기학회논문지
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• 제67권1호
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• pp.29-37
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• 2018

Inrush current and fault current in a transformer need to be distinguished from one another. In order to do this, KEPCO uses a 2nd harmonic restraint/block method. We use two setting values for 2nd harmonic restraint; 15% and 10%. We also apply per-phase blocking method among various harmonic restraint methods. If the transformer is located at the radial system, we adjust 10% in the 2nd harmonic restraint, but this method is not enough to prevent mal-operations of the current differential relay and let us spend more time to change setting value again as the power system changes. In this paper, a more reasonable setting value for a 2nd harmonic blocking scheme in KEPCO is proposed. To present a proposed method, the fault data of the current differential relays which have occurred since 2009 are analyzed. To evaluate the performance of the proposed method, the results of the RTDS test for the current differential relay of the transformer by KEPCO are analyzed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.619-625
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• 2008

Electrical Power supply System conditions of korea high speed train consists of main transformer, four AC-DC PWM converter of Auxiliary Block, Battery Charger in Power Car and Trailer Car, Trailer Inverter, Auxiliary inverter. Main transformer, at nominal voltage of 25kv supplied to secondary winding nominal output Voltage 383Vac, The Auxiliary block consists of AC-DC converters for generating 670VDC power, Auxiliary inverters for ventilation and air compressor, Trailer car inverter provide three phase power supplies at 440Vac for air conditioning and heating. The Battery charger Trailer and Power car supplies 72VDC all necessary equipment to energize the trainset equipment and suppy essential control. This Paper introduces the combined test results of the power supply system for korea high speed train. The main purpose of this combined test is to verify the performance of the power supply system that is designed to operate up to full load test.

• 전기학회논문지
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• 제57권10호
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• pp.1759-1766
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• 2008

According to the increase of power demand and expansion of downtown, it is necessary to install transformers additionally in operating substations and construct substations in residential area. But the public complaint has been increased due to the transformer noise of the substation. KEPCO has used a vibration preventing pad, various soundproof walls and an encloser to transformers in outdoor substations, and a soundproof door, shutter and wind-path soundproof equipment in indoor substations to block the sound propagation from the transformers. But these noise reduction methods are not satisfied. It should be considered to reduce transformer noise itself. In this paper, we investigated tank noise reduction techniques to develope a low noise transformer. According to the mode analysis of transformer tank, we found out characteristics and locations of noise on the tank, and it's nature vibration was also analysed. On the basis of these analysis, reinforcement equipment was installed around transformer tank, and ellipse shape tank was changed to round shape tank. The effect of noise reduction was evaluated using noise generation source.

• 한국정보통신학회논문지
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• 제26권4호
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• pp.533-540
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• 2022

전문의는 피부암을 조기에 발견하기 위해 피부경을 사용하여 진단하지만 다양한 형태로 인해 피부 병변을 판단하는 데 어려움이 있다. 최근 높은 성능을 보인 딥러닝을 이용한 피부 병변 분할 방법이 제안되었지만 피부와 피부 병변 경계가 명확하지 않아서 피부 병변을 분할하는 데 문제점이 있었다. 이러한 문제를 개선하기 위해 제안하는 방법은 효과적으로 피부 병변을 분할하기 위해 트랜스포머 블록을 구성하였으며, 네트워크의 각 계층마다 윤곽선 디코더를 구성하여 피부 병변을 자세히 분할하였다. 실험 결과, 제안하는 방법은 기존의 방법보다 Dice coefficient 기준 0.041 ~ 0.071, Jaccard Index 기준 0.067 ~ 0.112의 성능 향상을 보인다.

• 전기학회논문지
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• 제57권11호
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• pp.1962-1969
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• 2008

According to the increase of power demand and expansion of downtown, it is necessary to install transformers additionally in operating substations and construct substations in residential area. But the public complaint is increased due to the transformer noise of the substation. KEPCO has used a vibration preventing pad, various soundproof walls and an encloser to transformers in outdoor substations, and a soundproof door, shutter and wind-path soundproof equipment in indoor substations to block the sound propagation of the transformers. But these noise reduction methods are not satisfied. It should be considered to reduce transformer noise itself. In this paper, we investigated core noise reduction techniques to develope a low noise transformer. The techniques to reduce core noise of the transformer are application of high permeability grain oriented silicon sheets, decrease of magnetic flux density of core, application of 6step-lap core stacking method, improvement of core binding method(binding addition, band fixing) and application of rubber damper in oder to reduce transmission of core vibration, etc.

• 한국지능시스템학회논문지
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• 제8권5호
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• pp.72-82
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• 1998

Power transformer protective relay should block the tripping during magnetizing imrush and rapidly operate the tripping during internal faults. But traditional approaches maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmounic component. To enhance the fault detection sensitivities of conventional technuques, flux-differential current derivative curve by fuzzy theory approaches is used. This paper deals with fuzzy logic based protective relaying for power transformer. The proposed fuzzy based relaying algorithm consisits of flux-differential current derivative curve, harmonics restraint, and precentage differential characteristic curv. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.