• 한국초전도ㆍ저온공학회논문지
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• 제16권4호
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• pp.62-65
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• 2014

To minimize most heat loss of current lead for high-temperature superconducting (HTS) rotating machine, the choice of conductor properties and lead geometry - such as length, cross section, and cooling surface area - are one of the various significant factors must be selected. Therefore, an optimal lead for large scale of HTS rotating machine has presented before. Not let up with these trends, this paper continues to improve of diminishing heat loss for HTS part according to different model. It also determines the simplification conditions for an evaluation of the main flux flow loss and eddy current loss transient characteristics during charging and discharging period.

• International Journal of Contents
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• 제2권3호
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• pp.6-10
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• 2006

Small molecule OLED devices were fabricated and the electro-optical characteristics were analyzed. The luminance and color coordinate of the fabricated OLED device were $24,390cd/m^2$ and (x=0.15, y=0.22), respectively. Current efficiency of 6.8 cd/A and power efficiency of 2.4 lm/W were also obtained under DC operating condition. Transient light intensity was also measured by using Si photodiode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.381-382
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• 2008

This paper presents a novel scheme for reducing an asymmetry current with SFCL (Superconducting Fault Current Limiter) operation during transient period, when a fault occurs in power systems. The main idea is installation an auxiliary SFCL with characteristics, which reduces the asymmetry fault current in first half cycle before the operating of main SFCL. For proper activities of SFCLs, the principle of asymmetry current nature is reviewed. A scheme of asymmetry components reduction with SFCL is then explained. The EMTP/ATPDraw model of SFCLs using MODELS language developed and simulated to verify the performance and effectiveness.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.53-58
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• 2002

Sheath circulating current is increased as the change of sheath mutual impedance which is caused by imbalance of cable system, and different section length between joint box. If excessive current flows in sheath. sheath loss will be increased and then transmission capacity of underground transmission system is reduced. Accordingly, This paper proposed sheath current reduction device using resistor and reactor and proved the reduction effect of that device using EMTP/ATP. And also in this paper, when transients are occurred at the underground system with reduction device by ground fault and lightning surge. we analyzes transient effect of system variously. From this result. authors establish the protection methods of sheath circulating current reduction device.

• 전력전자학회논문지
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• 제27권4호
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• pp.339-347
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• 2022

This study proposes the mitigation method for overcurrent and oscillation motor current in an active short-circuit operation. This operation is attracting attention as the safe state of electric vehicle traction inverters. However, the active short-circuit operation generates oscillation and overcurrent of motor currents during a transient state. The proposed method uses two different safe states in PMSM, such as active short circuit and freewheeling. The active short circuit is used for safe state in a steady state. To reduce the overshoot and oscillation, a freewheeling state is injected between active short-circuit operation by comparing the motor phase current with an analytically calculated steady-state motor current. Freewheeling state is only used in a transient state. The performance is demonstrated through simulations and experimental results. The peak current of the motor was reduced from 52 A to 40 A, and oscillation time was reduced.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권11호
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• pp.616-621
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• 2002

With biological effects by ELF (Extremely Low Frequency) magnetic field generated from power system, the transient magnetic field from electric appliances is a major issue presently. Because the transient magnetic field induces higher current than the power frequency field inside living bodies, transient magnetic field exposure has been much focused. In this paper, it is shown that transient magnetic field from electric home appliances can be characterized as magnetic dipole moment. In this method, the dipole moment vector is assumed by allowing an uncertainty of 6dB in the estimated field. A parameter M that represents biological interaction was applied also. The proposed method was applied to 7 types of appliances (hair drier, heater, VDT, etc.) and their equivalent magnetic dipole moment and harmonic components were estimated. As the results, the useful data for quantifying magnetic field distribution around electric appliances were obtained.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.88-91
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• 2009

For lightning currents, a grounding system shows the transient grounding impedance characteristics. A grounding system for protection against lightning should be evaluated by the transient grounding impedance, not it's ground resistance. The transient grounding impedance varies with the shape of ground electrode and earth characteristics as well as the waveform of lightning surge current. For the analysis and practical use of transient grounding impedance, the characteristics of transient grounding impedance should be analyzed theoretically and this paper suggests the theoretical analysis for the transient grounding impedance of counterpoise by using the distributed parameter circuit model. EMTP and Matlab are used to simulate the distributed parameter circuit model of counterpoise and the adequacy of the distributed parameter model of counterpoise is examined by comparing the simulated results with the measured results.

• 조명전기설비학회논문지
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• 제24권5호
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• pp.62-69
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• 2010

본 논문은 매설지선의 과도접지임피던스의 임펄스전류의 인가위치와 대지구조에 대한 의존성에 관한것으로 다른 저항률을 가지는 토양에 매설된 길이 25, 50[m]인 매설지선의 과도접지임피던스와 규약접지 임피던스를 임펄스전류의 상승시간에 따라 측정하고 분석하였다. 그 결과, 매설지선의 과도접지임피던스는 유도성을 나타냈으며, 규약접지임피던스는 과도접지임피던스와 비슷한 경향성을 보였다. 매설지선의 접지저항은 임펄스전류의 인가위치에 관계없지만 특히 과도접지임피던스와 규약접지임피던스는 짧은 시간영역에서 임펄스전류의 인가위치와 대지저항률에 의존적이었다.

• Journal of Power Electronics
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• 제16권1호
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• pp.227-237
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• 2016

A novel digital current control strategy for digitally controlled DC-DC switching converters, referred to as Adjacent Cycle Sampling (ACS), is proposed in this paper. For the ACS current control strategy, the available time interval from sampling the current to updating the duty ratio, is approximately one switching cycle. In addition, it is independent of the duty ratio. As a result, the contradiction between the processing speed of the hardware and the transient response speed can be effectively relaxed by using the ACS current control strategy. For digitally controlled buck DC-DC switching converters with trailing-edge modulation, digital current control algorithms with the ACS control strategy are derived for three different control objectives. These objectives are the valley, average, and peak inductor currents. In addition, the sub-harmonic oscillations of the above current control algorithms are analyzed and eliminated by using the digital slope compensation (DSC) method. Experimental results based on a FPGA are given, which verify the theoretical analysis results very well. It can be concluded that the ACS control has a faster transient response speed than the time delay control, and that its requirements for hardware processing speed can be reduced when compared with the deadbeat control. Therefore, it promises to be one of the key technologies for high-frequency DC-DC switching converters.

• 조명전기설비학회논문지
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• 제22권6호
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• pp.100-108
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• 2008

접지전극의 형태, 크기, 재질 및 임펄스전류의 형상에 따라 변화하는 과도접지임피던스는 접지시스템의 성능에 중요한 영향을 미친다. 본 논문은 기존의 실효임펄스임피던스가 실제 과도접지임피던스를 얼마나 효과적으로 나타내고 있는가에 대한 분석과 보다 효과적인 과도접지임피던스 평가방법에 대하여 실험적인 결과를 제시하였다. 실험에 사용된 접지전극은 저항성분과 인덕턴스를 포함한 모의 접지전극과 1[m] 탄소접지봉, 9[m] 일반동봉 그리고 40[m] 매설지선이며, 가변주파수 전류와 임펄스전류에 의한 접지임피던스를 각각 측정하였다. 각각의 값을 비교 했을 때 기존의 실효임펄스임피던스의 값보다는 전압의 최대 값과 전류의 최대 값을 이용하여 과도접지임피던스를 구한 임피던스 값($Z_1$)이 등가주파수에 해당하는 가변주파수 전류에 의해 구해진 접지임피던스에 근접함을 확인하였다.