• 한국전기전자재료학회논문지
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• 제22권12호
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• pp.1073-1077
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• 2009

The iron core, which comprises the superconducting fault current limiter (SFCL) using magnetic coupling of coils, can be operated in the saturation region, especially at the initial fault period. This operation of the iron core in the saturation region deteriorates the fault current limiting operation of the SFCL. To solve the saturation problem of the SFCL using magnetic coupling of coils, the iron core with two magnetic paths, which has an air-gap in one of them, was adopted. In this paper, the hysteresis characteristics of SFCL using magnetic coupling of coils, which were wound in the iron core with two magnetic paths, were analyzed. Through comparative analysis on the hysteresis characteristics of the iron core comprising SFCL, the hysteresis characteristics of the iron core with two magnetic paths were confirmed to be kept in the non-saturation region during the fault period and thus, the effective fault current limiting operation of the SFCL using the magnetic coupling of coils could be performed.

• International journal of advanced smart convergence
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• 제8권4호
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• pp.138-146
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• 2019

In this paper, we proposed a soft-switched synchronous buck converter, which can perform charging the battery. The proposed converter has low switching loss even at high frequency operation due to its soft switching characteristics. The converter operates in synchronous mode to minimize conduction loss, resulting in small conduction loss, also. In this reason, the efficiency of the converter can be greatly improved even in high frequency. The size and weight of the converter can be reduced by high frequency operation of the converter. In this paper, we designed a battery charger with a switching frequency of 100 kHz. The designed converter also simulated to prove the converter's characteristics of synchronous operation as well as soft switching operation. The simulation shows that the proposed converter always meets the soft switching conditions of turning on and off switching in the zero voltage and zero current states. Therefore, simulation results have confirmed that the proposed battery charger had soft switching characteristics. The simulation results for transient response to charge current for the designed converter show that the converter responds to charge current commands quickly within 0.05 ms.

• 전기학회논문지
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• 제67권7호
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• pp.981-986
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• 2018

AC(alternating current) CB(circuit breaker) at the fault occurred in the existing AC distribution system is limiting the fault current through zero cross-point. However, DC(direct current) CB does not have zero cross-point. Therefore, arc occurred by on-off operation of DC CB is very huge. Nowadays, many research team are studying the way to decrease breaking time, which is one of the essential conditions in DC CB. We suggested novel arc-induction type DC CB in this paper. The proposed arc-induction type DC CB is composed of the mechanical Arc ring and DC CB. We confirmed the operation of arc-induction type DC CB through the HFSS(High Frequency Structure Simulator) 3D simulation program and performed the experiment for operation characteristics. Results showed that arcing time of the arc-induction type DC CB by using induction ring was faster than existing mechanical DC CB. On the transient system, we confirmed stable operation characteristics of the arc-induction type DC CB through the simulation and experimental results. We expect that the proposed arc-induction type DC CB technology is will go to stay ahead of the existing DC CB technology.

• 한국해안·해양공학회논문집
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• 제25권4호
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• pp.219-235
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• 2013

시화조력발전소 가동에 따른 인근 해역의 해수특성 및 성층변화를 파악하기 위하여 3차원 수치모델을 이용하였다. 여름철의 경우, 하천을 통해 유입되는 담수의 영향으로 인해 시화호 내측의 밀도는 수온보다는 염분에 의해 더 영향을 받는다. 조력발전소 가동 전에 호 내측에서는 외해에 비해 상대적으로 고온, 저염의 해수특성을 보이는 반면에 조력발전소 가동 시에는 호 내측의 수온이 소폭 낮아지고 염분이 증가하는 경향을 보인다. 또한 조력발전소 가동 시 해수의 유입 유출이 활발해짐에 따라 혼합효과의 증대로 인해 시화호의 밀도는 증가하고 성층은 약화되는 것으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.463-466
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• 2000

According to the development of the semiconductor micro device technology, IC chip trends the high integrated, low power tendency. Nowadays, it can be showed the tendency of single chip in system level. But in the system level, IC operates by multi power supply voltages. So, semiconductor process is necessary for these multi power operation. Therefore, in this paper, dual gate high voltage device that operate by multi power supply of 5V and 20V fabricated in the 0.5${\mu}{\textrm}{m}$ CMOS process technology and its electrical characteristics were analyzed. The result showed that the characteristics of the 5V device almost met with the SPICE simulation, the SPICE parameters are the same as the single 5V device process. And the characteristics of 20V device showed that gate length 3um device was available without degradation. Its current was 520uA/um, 350uA/um for NMOS, PMOS and the breakdown voltages were 25V, 28V.

• 전기학회논문지P
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• 제59권4호
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• pp.477-480
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• 2010

Fault current in power system is expected to increase by demand of power capacity. Therefore, when the fault occurred, fault current was increased in the power system. Many studies have been progressed to limit the fault current. Superconducting fault current limiter (SFCL) is one of them which has been studied in worldwide. In this paper, we will analyze characteristics of a transformer-type SFCL by reclosing operation when the voltage increases. Twice opening times in the reclosing of circuit breaker were set as the 0.5 and 15 seconds, respectively. Turn's number of primary and secondary coils set 4:2 and we increased voltages from 120V to 280V for each experiment. By the current waveform, maximum fault current in second and third cycles was lowered when the voltage was increased. In the recovery waveform, recovery time was increased as the voltage was increased. The reason was that power burden of the SFCL increased when consumption power was increased, so the time to get back to SFCL took longer. We compared the characteristics of a resistive-type and transformer-type SFCL. As a result, we found that the fault current of a transformer-type was lower than resistive-type and recovery time of the SFCL was shorter. Consequently, transformer-type SFCL was more profitable for limitation of fault current and recovery time under the same condition for reclosing operation.

• 전기의세계
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• 제28권5호
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• pp.49-55
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• 1979

During severe emergencies which result in insufficient generation to meet load, an automatic load shedding method considering the spinning and operating reserve can establish the optimum system operation. This paper presents methods and results of a study on the optimum operating scheme with spinning and operating reserve power in case of outage of large generator units to prevent frequency decay and continue stable operation. This study covers following three parts 1) Analysis of spinning reserve characteristics 2) Determination of operating reserve requirements 3) Development of the optimum load shedding programs By this study the optimum system operating method was recommended for reliable operation of power system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.123-128
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• 2012

작동 시퀀스에 따른 핀틀 노즐의 성능 특성을 비교하였다. 비정상상태 이동격자 수치해석 기법을 이용하여 시간에 따른 핀틀의 위치 변화를 고려하였으며, 다양한 핀틀 형상과 작동 시퀀스에 따른 성능 응답지연 및 민감도 분석을 수행하였다. 연소실 내부의 압력 상승률과 압력진동이 성능에 미치는 영향을 관찰하기 위하여, 노즐 목에 핀틀이 머무르는 시간이 다른 세 가지의 작동 시퀀스를 고려하였다. 핀틀이 노즐 목에 머무르지 않는 경우(case 1), 0.5초 머무를 경우(case 2) 그리고 노즐 목 위치에 계속 정지해 있을 경우(case 3)에 대해 비교하였고, 이를 통해 작동 시퀀스 및 핀틀 형상에 따른 동특성 연구를 수행하여 추력 특성 변화를 도출하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.633-637
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• 2007

Bimodal Tram is the newly developed vehicle for both the tracked way and the public road. Its operation system has some characteristics including BIS(bus information system)/BMS(bus management system) based on ITS(intelligent Transportation system) which is used presently in public transportation operation system. One of them is more accurate vehicle fleet control based on both magnetic maker position reference system and GPS(global positioning system) and the other is automatic vehicle control for emergency situations by the Bimodal Tram operation system which will be performed by the unified control and operation center. This paper has investigated the requirements and functional definitions necessary to construct the unified control and operation center for Bimodal Tram operation system which will be more efficient and secure public transportation system than the conventional ones.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.50-56
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• 2006

Residual gas fraction in a combustion process is very crucial to improve combustion and cyclic variations. Especially, the residual gas fraction is strongly affected by backflow of the residual gas during the valve overlap period in an idle operation. Therefore, it is one of the most interesting that valve timings can affect flow characteristics of gas exchange process, especially during idle operation. This analysis investigates residual gas fraction with respect to valve timing changes which is critical for combustion efficiency and engine performance. Flow characteristics of residual gas by changing intake and exhaust valve timing are calculated by CFD methodology during an idle operation in an SI engine. It is analyzed that retarded EVO and advanced IVO results in the increase of valve overlap period and consequently, residual gas fraction. Futhermore, changes in IVO have stronger effects on variation of residual gas fraction.