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정동철(Dong Chul Chung) 대한전기학회 2012 전기학회논문지 Vol.61 No.12
In this work, we investigated quench characteristics of matrix-type superconducting fault current limiters (MFCLs) according to the turn number of reactors. The reactors used in MFCLs apply magnetic field to superconducting elements within reactors when fault currents surge into MFCL systems. It makes the fast and simultaneous quenches between superconducting elements. Also reactors decrease the fault power burden of superconducting elements by bypassing the partial fault currents to itself, when quench occurs. These structure proposed in this work can be expected to achieve much more current limiting capacity even though it uses less superconductors compared with other type SFCLs. Three reactors were made by Bakelite. These reactors with the turn number of 190, 380 and 570, had the length of 270 mm and diameter of 80 mm. We reported experimental results, including fault currents, fault voltages and resistance in superconducting elements according to the turn number of reactors. We confirmed that experimental results will be useful in next future plan for the real power grid.
삼선 지락사고 발생시 매트릭스형 한류기용 리액터의 전자장 분포 해석
정동철(Dong Chul Chung),한태희(Tae Hee Han) 대한전기학회 2011 전기학회논문지 Vol.60 No.2
In this paper we reported the characteristics of 1 line, 2 lines and 3 lines-to-ground fault of matrix-type SFCLs (MFCLs) and the electromagnetic field distribution of reactors for MFCLs under the same cases of ground faults. To do this, we fabricated MFCLs with 6 reactors for 3 phases. Each reactor had the length of 270 ㎜ and diameter of 80 ㎜. 6 reactors were made by Bakelite. We reported experimental results, including fault currents, fault voltages and magnetic field distribution according to phase differences between each phase. We confirmed that experimental results will be useful in next future plan for real power grid.
고온초전도체를 이용한 가지 형태 3 ㏈ 방향성 결합기 설계 및 특성해석
정동철(Dong Chul Chung),최명호(Myoung Ho Choi) 대한전기학회 2010 전기학회논문지 Vol.59 No.1
In this work, we presented the characterization of 3 ㏈ branch type directional couplers by using High-Tc superconducting thin films. To do this, we deposited YBCO superconducting thin films on MgO substrates by using rf-magnetron sputtering techniques. The designed center frequency was 408 MHz and the designed passband was 20 ㎒. Also we designed 3 ㏈ Power difference and 90° of phase difference between port 3 and port 4. The even and odd mode analysis were used to characterize our directional couplers and em Sonnet (full wave analysis program) was utilized to the optimum design. We reported experimental results, including a center frequency, passband, half power characteristics and phase differences. We confirmed that experimental results were in good agreements with characterization by using full wave analysis program.
고온초전도체를 이용한 마이크로파 전력분배기의 소형화 개발
정동철(Dong-Chul Chung),유병화(Byung-Hwa Yoo),곽민환(Min-Hwan Kwak),강광용(Gwang-Yong Kang),한병성(Byoung-Sung Han) 대한전기학회 2009 전기학회논문지 P Vol.58 No.3
In this paper, We report the miniaturization of superconducting microwave power dividers based on lumped element equivalent circuits. To do this, we analyzed a conventional branch-type power divider by using an ABCD matrix under even and odd mode excitation. Then, we calculated each lumped element impedance throughout this analysis of a transmission line matrix. Also we simulated our equivalent circuits made of lumped elements by using a full wave analysis, em Sonnet. Our deign of microwave power divider based on simulated results was fabricated on high-Tc superconducting thin films deposited on MgO substrate. Experimental results were reported in terms of bandwidth, center frequency, and phase difference between S21 and S31. We confirm that our design will be useful in the future microwave power systum.
전자장 해석을 통한 매트릭스형 한류기용 리액터 설계 및 특성해석
정동철(Dong-Chul Chung),윤창훈(Chang-Hun Yun),최효상(Hyo-Sang Choi) 대한전기학회 2009 전기학회논문지 P Vol.58 No.2
In this paper, we performed the optimum design of reactors for matrix-type superconducting-fault current limiters (SFCLs), using electromagnetic analysis tools. We decided a optimun position within a reactor for superconducting elements of current-limiting parts and trigger parts from the calculation of magnetic flux internsity for reactor structures. Also we decided effective distance length between two reactors through the analysis of the distribution of magnetic field, according to distance lengths between them. We designed and characterized matrix-type SFCLs, based on our optimum design of a reactor. We confirmed uniform distribution of a fault current, resulted from the improvement of simultaneous quench characteristics within our matrix-type SFCL.
AC PDP에서의 대폭소거방식을 이용한 선택적 초기화 파형
鄭東哲(Dong Cheol Jeong),黃琪雄(Ki-Woong Whang) 대한전기학회 2007 전기학회논문지 Vol.56 No.12
In this paper, we propose a newly developed selective reset waveform of a ac PDP using the wide erase pulse technique with the control of address bias voltage. Although it is generally understood that the wide pulse erasing methode shows the narrow driving margin in an opposite discharge type ac PDP, we could obtain a moderate driving margin in a 3-electrode surface discharge type ac PDP. The obtained driving margin shows a strong dependency on the sustain voltage and the address bias voltage. The lower the sustain and the address bias voltage, the wider the driving margin. The pulse width of the proposed waveform is only 10㎲, which gives additional time to the sustain period, hence increases the brightness. The brightness and contrast ratio increase about 20% together comparing to the conventional ramp type selective reset waveform with the driving scheme of 10 subfield ADS method. The driving margin was measured with the line by line addressed pattern on the white test panel of 2inch diagonal size and the discharge gas was Ne+Xe4%, 400torr.