• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.117-122
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• 2005

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency converter bridge, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter bridge, and an AC filter. The high frequency converter bridge switching at 20kHz is used to generate bipolar PWM pulse, and the high frequency transformer raise its voltage twice, which is subsequently rectified by diode bridge rectifiers to result in a full-wave rectified sine wave. Finally, it is unfolded by a low frequency inverter bridge to result in a 60Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than the other systems due to elimination of 60Hz transformer.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.278-281
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• 2013

The effects of electric field frequency on the AC electrical treeing phenomena in an epoxy/layered silicate (1.5 wt%) were investigated in a needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy-base resin with AC electric field apparatus. To measure the treeing initiation and propagation- and the breakdown rate, a constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500, and 1,000 Hz) was applied to the specimen in the needle-plate electrode specimen in an insulating oil bath at $130^{\circ}C$. At 60 Hz, the treeing initiation time was 12 min, the propagation rate was $0.24{\times}10^{-3}$ mm/min, and the morphology was a dense branch type. As the electric field frequency increased, the treeing initiation time decreased and the propagation rate increased. At 1,000 Hz, the treeing initiation time was 5 min, the propagation rate was $0.30{\times}10^{-3}$ mm/min, and the morphology was a dense bush type.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.87-90
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• 2014

The effects of electric field frequency on the ac electrical treeing phenomena in an epoxy/reactive diluent/layered silicate (1.5 wt%) were carried out, in needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy base resin, by using our ac electric field apparatus. To measure the treeing propagation rate, constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500 and 1,000 Hz) was applied to the specimen, in needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. As the electric field frequency increased, the treeing propagation rate increased. At 500 Hz, the treeing propagation rate of the epoxy/PG/nanosilicate system was $0.41{\times}10^{-3}$ mm/min, which was 3.4 times slower than that of the epoxy/PG system. The electrical treeing morphology was dense bush type at 60 Hz; however, as the frequency increased, the bush type was changed to branch type, having few branches, with very slow propagation rate.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2083_2084
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• 2009

본 연구에서는 변류기 비교측정 시스템과 정밀저항을 이용 하여 변류기의 오차에 연관되는 인자를 측정함으로써 피측정 변류기의 절대 평가를 하고 그 결과를 이용하여 표준 변류기를 평가 하였다. 한편 기존에 60 Hz 에 적용하였던 실험을 이번 실험에서는 60 Hz 뿐만 아니라 50 Hz 까지 확장하여 실험 하였다. 이 기술의 타당성을 검증하기 위해 실험에 사용된 동일한 변류기에 대한 해외 국가 표준기관의 비오차 및 위상오차와 비교 하였고 그 차이값이 확장 불확도 내에서 일치 함을 확인 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.303-306
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• 1998

Electroluminescence is occurred when phosphor is located in electric field. Object of this research show powder electroluminescent device (PELD) for high brightness compared with conventional PELD. Single layer of PELD structured as follow (ITO/phosphor + dielectric/silver paste). To investigate optical properties of PELDS, EL spectrum, CIE coordinate system, Brightness of PELDs was measured. The suitable ratio between phosphor and dielectric in single layer of PELD was 7:3(phosphor: dielectric). At 200 V4OO Hz, high performance of PELD which had ratio of 7:3

• Journal of the Optical Society of Korea
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• v.16 no.2
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• pp.181-184
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• 2012

We report, for the first time, operation frequency dependence of current density-voltage ($J_{OLED}-V_{OLED}$) shift for multi-layer organic light-emitting diodes (OLEDs). When the OLEDs were electrically stressed for 21 hours with 50% duty voltage pulses at 60, 120, 240, and 360 Hz, the JOLED-VOLED shifts were suppressed by half for 360 Hz operation compared with 60 Hz operation, but with little change in emission efficiencies. This frequency dependent $J_{OLED}-V_{OLED}$ shift is believed to be commonly observed for typical multi-layer OLEDs and can be used to further improve lifetime of digitally-driven active-matrix OLED displays.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.829-834
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• 2016

Coil specimens were prepared by continuous coating on a copper wire with flexible PAI (polyamideimide) and PAI/nanosilica (5 wt%) varnish and thermally aged at 150, 200 and $250^{\circ}C$ for 5, 10 and 15 days, respectively. AC insulation breakdown voltage was investigated under inverter surge condition at 60 Hz and 1,000 Hz and insulation breakdown voltage decreased with increasing aging temperature and aging time at each 60 and 1,000 Hz.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.360-363
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• 2001

The conventional 60(Hz) power supply for driving magnetron in microwave oven has disadvantages of heavy weight and low efficiency due to 60(Hz) High Voltage Transformer(HVT), capacitor and the phase control of thyristors with open-loop controller. To alleviate these disadvantages, this paper proposes a 20(kHz) phase-shifted(PS) Full-Bridge(FB) Zero- voltage-Switched(ZVS) PWM converter to drive a 600(W) magnetron in an 1(kW) microwave oven and to control the average anode current.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.35-37
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• 2015

본 논문은 전력구 내 지중선에서 발생하는 상용주파수(60 Hz) 자기장을 이용한 2 W급 무선전력 수신장치를 제안한다. 제안하는 수신장치는 자성체와 구리도선을 포함하는 수신 코일, 장치의 개폐를 위한 손잡이, 직렬공진회로 및 정류기를 포함하는 부가회로로 구성된다. 수신장치는 3상 지중선 중 하나에 설치되어 전력구 내 조명 및 온습도 센서를 구동하는데 사용 가능하다. 수신장치의 자성체로는 높은 기계적 강도 및 포화 자속밀도를 가지는 규소강판 박편이 사용되었으며, 직렬공진회로를 사용하여 최대전력을 수신하였다. 수신장치의 공진회로는 3 이하의 낮은 공진계수를 가지기에 50 Hz 및 60 Hz 지중선에 범용으로 사용이 가능하다. 사용된 규소강판 및 구리선의 무게와 가격의 곱을 성능지수(Figure of Merit)로 선정하여 이를 최소화하는 설계를 수행하였다. 제작된 시작품의 무게는 약 750 g중으로 2.2 W LED부하 구동이 가능하며, 이때 지중선의 전류는 $100A_{rms}$로 가정하였다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.1
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• pp.23-29
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• 2005

This paper presents the characteristics of leakage currents flowing through ZinC Oxide(ZnO) surge arrester blocks under mixed direct and 60 Hz alternating voltages. A mixed voltage, in which an alternating voltage is superimposed upon a direct voltage, appears on the HVDC system network. The mixed direct and alternating voltage generator with a peak open-circuit of 10 kV was designed and fabricated. The leakage currents and V-I curves for the fine and used ZnO surge arrester blocks were measured as a function of the voltage ratio k, where the voltage ratio k is defined as the ratio of the peak of alternating voltage to the peak of the mixed voltages. The resistive component in the leakage current in the low conduction region is significantly increased with increasing the voltage ratio k. The V-I characteristic curves for the mixed voltages lies between the direct and alternating characteristics, and the cross-over phenomenon in the high conduction region was appeared.