• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.280-289
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• 2015

A high-efficiency full-bridge DC-DC converter with a current-doubler rectifier and an asymmetric pulse-width modulation is proposed. Through the asymmetric pulse-width modulation, the proposed converter achieves zero-voltage switching of power switches without the circulating currents. The proposed converter reduces the output current ripple through the current-doubler rectifier. A control strategy is suggested for the proposed converter to charge battery banks. A constant current and constant voltage charging is performed. The proposed converter achieved a higher efficiency compared with the conventional full-bridge DC-DC converter with a phase-shift modulation. The performance of the proposed converter is evaluated by the experimental results for a 1.0 kW prototype circuit.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.320-321
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• 2008

In this paper, new simulator based on EMTP was introduced for simulation of underground power cable system. The newly developed simulator was named as Power Cable Simulator(PCS), and it can simulate the various normal conditions including sheath circulating current. It is also easier to use than conventional software, such as EMTP and CabSim, because all the data for calculating the cable parameters are stored in a database(DB) within a PCS. In addition, the accuracy of PCS is also proved through the comparison between the calculation and simulation of sheath current.

• Plant Journal
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• v.9 no.1
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• pp.43-49
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• 2013

In this study, the natural frequency of the actual operating vertical pump in the P combined cycle power plant is measured and the cause of high vibration is determined by using fluid-structure coupled vibration theory. Choosing the vibration reduction plan suited for field conditions and using the numerical analysis verify effectiveness of the plan. The plan is applied to the actual pump and the empirical experiments are conducted.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.220-221
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• 2013

UPS 부하시험시 또는 DC 전압원 방전 시험시에 사용되는 일반 저항 또는 역률 부하 시험기를 사용하지 않고 UPS 내부 역변환부 출력전원을 출력 스위치와 바이패스 스위치를 통해서 순변환부 입력전원에 재공급함으로써 시험용 저항부하기 또는 역률 부하 시험기와 같이 모든 에너지를 열로 소비하지 않고 순변환부 측으로 재 순환시켜서 UPS 부하시험 시 입력 전원용량이 UPS 최소 내부 손실분만으로도 이미 현장 설치 및 운영 중인 UPS에서도 별도의 부하 시험기 및 시험용 케이블을 이동, 설치하지 않고 주기적인 UPS 점검 시, 적용 가능한 에너지 절감형 부하시험기법에 관해 연구하였다.

• Journal of Power Electronics
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• v.16 no.1
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• pp.93-101
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• 2016

A new four-primary-switch diode clamped soft switching three-level DC-DC converter (TLDC) with full zero-voltage switching (ZVS) load range and TL secondary voltage waveform is proposed. The operation principle and characteristics of the presented converter are discussed, and experimental results are consistent with theoretical predictions. The improvements of the proposed converter include a simple and compact primary structure, TL secondary rectified voltage waveform, wide load range ZVS for all primary switches, and full output-regulated range with soft switching operation. The proposed converter also has some disadvantages. The VA rating of the transformer is slightly larger than that of conventional TLDCs in variable input and constant output mode. The conduction loss of the primary coil is slightly higher because an air gap is inserted into the magnetic cores of the transformer. Finally, the secondary circuit is slightly complex.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.2030-2031
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• 2007

This paper is purpose to understand the surge property for the shorted turn or shorted strand in high voltage motor stator windings. a shorted turn in high voltage motor windings causes a huge circulating current. and overheat windings, consequently burns the motor. a few shorted strands not cause winding failure immediately, but they increase the winding loss and temperature increase due to contact resistance. We carried out the surge test for three cases, normal winding, shorted turn winding and shorted strand winding. and we analyzed the test result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1020-1025
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• 2001

Vertical canned pumps are usually applied in the power plant to transport fluids that the available suction pressure is low at the condensate system and the circulating-water system. The top of the motor driver is 5.5m above the base and the barrel and drop column extend even further below the ground. While this size and configuration may produce an efficient pumping system, it also introduces several dynamic problems which must be considered in order to obtain a reliable operation. The main problem is that the vibrational mode of the long flexible cantilever structure above the ground exist near the operational characteristics of the condensate debris system. This system's trouble has been showed at 2,086 hp condensate water loading pumps in a nuclear power plant.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.5-6
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• 2016

This paper introduces a high efficiency bidirectional resonant converter using an additional LC auxiliary circuit for dcdistribution applications. The LC auxiliary circuit operates as a variable inductor and the additional LC circuit helps to increase the effective magnetizing inductance, thereby reducing the turn-off and primary circulating current. A 5 kW bidirectional converter for dc-distribution system is implemented to verify the validity of the proposed method. The experimental results show the high efficiency characteristics of the proposed converter over the wide range of load in both direction of power flow. The maximum efficiency of the proposed system was 98.1 % at 3 kW.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.32-33
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• 2010

This paper describes a droop control method for the autonomous operation of DC distribution system using distributed generations and energy storage. The method suppress the circulating current, and each unit could be controlled autonomously without communication system. Detailed model of wind power generation, photo-voltaic generation, fuel-cell generation and battery was implemented with the user-defined model of PSCAD/EMTDC software that is coded with C-language. The simulation and experimental results confirms that the proposed DC distribution system make it feasible to provide power to the load stably and verify effectiveness of the proposed method.

• Nuclear Engineering and Technology
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• v.45 no.4
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• pp.459-468
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• 2013

During a station blackout (SBO), the initiating event is a loss of Class IV and Class III power, causing the loss of the pumps, used in systems such as the primary heat transporting system (PHTS), moderator cooling, shield cooling, steam generator feed water, and re-circulating cooling water. The reference case of the SBO case does not credit any of these active heat sinks, but only relies on the passive heat sinks, particularly the initial water inventories of the PHTS, moderator, steam generator secondary side, end shields, and reactor vault. The reference analysis is followed by a series of sensitivity cases assuming certain system availabilities, in order to assess their mitigating effects. This paper also establishes the strategies to mitigate SBO accidents. Current studies and strategies use the computer code of the Integrated Severe Accident Analysis Code (ISAAC) for Wolsong plants. The analysis results demonstrate that appropriate strategies to mitigate SBO accidents are established and, in addition, the symptoms of the SBO processes are understood.