• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1492-1493
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• 2007

This paper represents the development of national standard(NS) for switching impulse(SI) voltage measuring system rated 500 kV. A traceability of the NS to the international standard could be achieved by the intercomparison test with PTB(Physikalisch-Technische Bundesansalt). According to the IEC 60060-2, a measurement uncertainty was assessed. As a result of the tests, the measurement uncertainty and the characteristics of step response were satisfied with the requisite for NS.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.933-934
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• 2007

We fabricated and tested a resistive type superconducting fault current limiter (SFCL) based on BSCCO-2212 bulk coils. Each bulk coils of the SFCL was designed to have the rated voltage of 220 $V_{rms}$ and the critical current($I_C$) of 320$\sim$340 A at 77K. Ten components in series, make the SFCL having the rated voltage of 2.2 $kV_{rms}$ for equal quench test. The fault test was conducted at an input voltage of 2.2 $kV_{rms}$ and fault current of 25 $kA_{rms}$. In addition, we examined the endurance characteristics for all bulk coils through repeat fault test. Test results shows that the SFCL successfully limited the fault current of 25$kA_{rms}$ to below $7{\sim}8kA_{p}$ within minimum 1.1msec after fault occurred. All bulk coils quenched together upon faults and shared the rated voltage evenly. The endurance test results show an equivalent among repeat fault test. During the quench process, average temperature of all bulk coils did not exceed 250 K, and the SFCL was totally safe during the whole operation.

• Journal of Power Electronics
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• v.16 no.2
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• pp.786-797
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• 2016

This paper describes the design and development of a novel semiconductor-based solid-state switch for damped oscillating voltage test system. The proposed switch is configured as two identical series-connected switch stacks, each of which comprising 10 series-connected IGBT function units. Each unit consists of one IGBT, a gate driver, and an auxiliary voltage sharing circuit. A single switch stack can block 20 kV-rated high voltage, and two stacks in series are proven applicable to 30 kV-rated high voltage. The turn-on speed of the switch is approximately 250 ns. A flyback topology-based power supply system with a front-end power factor correction is built for the drive circuit by loosely inductively coupling each unit with a ferrite core to the primary side of a power generator to obtain the advantages of galvanic isolation and compact size. After the simulation, measurement, and estimation of the parasitic effect on the gate driver, a prototype is assembled and tested under different operating regimes. Experimental results are presented to demonstrate the performance of the developed prototype.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1519-1520
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• 2006

This paper describes a selection and application recommendations of ZnO arresters on DC electric traction vehicles. We measured and analyzed the system voltages applied to arresters and the surge currents flowing arresters on DC electric traction vehicles under operation to decide the Continuous Operating Voltage($U_C$), the Rated Voltage($U_R$), and the Nominal Discharge Current($I_n$). System voltages measured up to 1,800 V during anti-breaking in 1,500 V-system, and surge currents were recorded up to 3 times per running-service-route and their magnitudes were ranges of $150A{\sim}2kA$. From these results and the standard EN50163, we proposed the Continuous Operating Voltage($U_C$) the Rated Voltage($U_R$) for the $1,500V_{dc}$ electric traction vehicles.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1387_1388
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• 2009

High accurate and stable 132 kV potential transformers (PTs) including 66 kV & 22 kV PT with stability of less than 0.0033 % for 13 month and with ratio error within $\pm$ 0.024 % at full rated voltage have been developed. The PTs are useful as the reference PT of the PT comparator system in the voltage range of 11 kV to 132 kV PT.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.56-58
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• 2018

본 논문에서는 낮은 스위치 전압정격과 넓은 전압범위를 갖는 800V/14V LDC용 새로운 소프트 스위칭 컨버터를 제안한다. 제안하는 컨버터는 입력이 직렬구조로써 입력전압의 절반으로 낮은 스위치의 전압정격을 갖기 때문에 600V의 Si-MOSFET를 사용할 수 있어 도통손실을 줄일 수 있으며 넓은 입력전압 및 부하영역에서 소프트 스위칭을 성취하여 높은 효율을 달성할 수 있고 변압기의 직렬연결로 된 커패시터로 인해 자화전류의 오프셋이 없다. 또한 2차 측의 DC 블로킹 커패시터에 인터리빙 방식을 적용하여 기존의 전류정격이 큰 문제를 해결하였다. 제안하는 소프트 스위칭 컨버터의 동작원리를 제시하고 시작품을 통해 본 논문의 타당성을 검증하였다.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.133-134
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• 2008

This paper describes a testing method to assess the reliability of the epoxy bushing used for the vacuum circuit breaker(VCB). Especially, in order to show the long-term durability of epoxy bushing in a short testing duration, the extremely accelerated electric stress applying test plan was adopted.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.403-404
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• 2014

전기 자동차 및 하이브리드 자동차는 차량의 12V 부하에 전원을 공급하고 12V 배터리를 충전시키기 위해 DC/DC 컨버터를 사용한다. 이 DC/DC컨버터를 LDC(Low voltage DC/DC Converter)라 한다. 본 논문에서는 Active Clamp 방식의 포워드 컨버터를 이용하여 소용량 LDC를 개발한 내용을 소개 하였다.

• Journal of the Korean Society of Food Culture
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• v.11 no.5
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• pp.663-671
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• 1996

The purpose of this study was to compare high-school students importance and performance toward restaurant service attributes for the marketing strategy development. Specific objectives were to: a) investigate restaurant patronage characteristics of high school students; b) identify the difference of patronage behavior among three types of restaurants; and c) analyze the importance and performance among three types of restaurants. A questionnaire was developed and hand-delivered to 400 students enrolled 9th grade in 4 different high schools in Seoul. A total of 320 students (80%) was responded to this study. The questionnaire was composed of two parts with 47 restaurant service attribute statements. Results of this study were as follows: 1. A total of 57% was female and 61% of respondents spent less than ￦5,000 per week on eating out. 2. The frequency of visiting the low-priced restaurant was 8.9 times per week. 3. Reasons for being a patronage to low- (${\geq}$￦2,000) and mid-priced ( <￦2,000 and ${\geq}$￦5,000) restaurants were hunger, appointment, and seeking favorites with freinds but the reason for high-priced (<￦5,000) restaurants was celebrating special days with parents. 4. The main source of information for selecting restaurants was family and friends, T.V. advertising, and bulletin board. 5. For the low-priced restaurants, food, hygiene, price, and location were rated as important; location, price, menu, and food were rated as satisfied. 6. For the mid-priced restaurants, hygiene, food, price, and menu were rated as important; food, hygiene, service, and menu were rated as satisfied. 7. For the high-priced restaurants, hygiene, food, and atmosphere were rated as important; food, hygiene, atmosphere, and menu were as satisfied. 8. According to paired t-test, the score gap between importance and performance was the highest in the hygiene attribute; differences were high with the low-priced and low with high-priced restaurants.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2069-2072
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• 1999

The extended 765 kV system may have severe electrical transients according to the interconnection of transmission lines and have long transmission line over 250 km. So we need to analyze the transient phenomena to confirm the insulation coordination which is designed for 765 kV project step I. In particular, this paper shows the analysis results of secondary arc extinction by HSGS (high speed ground switch) application. The EMTP/MODELS were used to simulation study of secondary arc phenomena. We had confirmed the TRV(transient recovery voltage) and rated current of HSGS which will be used in the KEPCO 765 kV system.