• Proceedings of the KSR Conference
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• 2008.06a
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• pp.311-315
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• 2008

Ground systems set the reference voltage level of circuit and system, and suppress Ground Potential Rise (GPR) by flowing fault currents to ground safely. There are several parameters which evaluate the performance of ground systems as ground resistance, touch voltage and step voltage. The touch and step voltages are especially important to ensure safety of human body. In this paper, we measured the touch and step voltages by injection of power frequency and surge current. Also correlation between touch and step voltages is compared and analyzed for the same ground systems.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.292-294
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• 2005

A new zero voltage switching (ZVS) 2-transformer boost converter is proposed in this paper. The proposed converter has the advantage that the magnetizing inductor of the transformer acts for the boost inductor without additional inductor. Moreover, ZVS of main switches and auxiliary switches can be achieved, and the switch turn-off surge problem of conventional isolated boost converter is effectively solved. The operational principle, DC voltage gain, and ZVS characteristics are analyzed. To confirm the validity of the proposed converter, simulation results with 200w, 24Vdc/200Vdc specification are presented.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.559-562
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• 2000

The problem of noise generation due to PWM switched-mode power converter has been widely noticed from the viewpoint of Electromagnetic Interference(EMI). Many kings of topologies for resonant converters have been developed both to overcome this noise problem and to attain high power efficiency. It is reported in references that resonant converters which are derived from PWM converter using resonant switch show much lower noise characteristics than PWM converter, and that current-mode resonant converter is more sensitive to stored charge in rectifying diode than voltage-mode counterpart concerning surge generation at diode’s turn-off. On the other hand, above mentioned resonant converters have defect of high-voltage stress on semiconductor switch and complicated circuit configuration. Hence, the simplified Forward-type resonant converter has been proposed and investigated due to its prominent features of simplicity of circuit configuration, low voltage stress and high stability. However, its noise characteristics still remain unknown. The purpose of this paper is to study quantitatively the noise characteristics of this simplified Forward-type resonant converter by experiment and analysis. The influence of parasitic elements and stored charge in rectifying diode on noise generation has been clarified.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.9
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• pp.437-443
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• 2005

This paper deals with an experimental study for Klippon reiay in Cheju-Heanam HVDC system Klippon relay was troubled many times for years, and Klippon relay's fault caused the HVDC system trip. So for several years, these reasons of Klippon relay fault were investigated. The malfunction of Klippon relay in Cheju-Haenam HVDC system has been caused by the incoming of random surge(current source and voltage source). This paper has stu야ed the theoretic리 analysis and experimental study of Klippon relay, and the solutions against the problems were suggested according to their causes. Among the problems, grounding problem was removed by one-point earth connection and by modification of grounding circuit. The effects of inrush current was removed by inserting the blocking diodes by series in Klippon relay circuits. Finally, The over-voltage induced on Klippon relay, by a relay excitation coil, was removed by inserting a free-wheeling diode in Parallel with the excitation coil.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.486-489
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• 1999

This paper deals with the design rule and performance results of the transient voltage blocking devices (TBD) for low-voltage mains on shipboard. The proposed TBD consists of metal oxide varistors (MOV) and L-C filter to improve noise-elimination performance. Three kinds of TBDs are fabricated and tested by using a combination surge generator which can produce the standard impulse current of 8/20${\mu}$s 2.1kA. As a reults, the proposed TBD with series L-C filter has more excellent transient blocking and noise reduction performance than the conventional TBDs.

• Journal of Power Electronics
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• v.5 no.3
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• pp.212-217
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• 2005

In order to correct the power boost topology has been used for easy control. But conventional boost topology has the following drawbacks: switching voltage surge, cross conduction current and right-half-plane zero of its control transfer function. Furthermore, in this topology the output voltage is always higher than the input voltage. As a result, a first-stage boost PFC converter needs to be connected with a second-stage DC-DC converter. A new topology which can be used as single stage PFC converter is proposed in this paper.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.198-199
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• 2017

This paper proposed a new control method for supercapacitor (SC) to compensate the pulse load transient and enhance the power quality of dc microgrid. By coordinating the operation frequency, the supercapacitor is controlled to handle the surge current component while the low-frequency current component is dealt with by remaining sources in the system. Based on the state of charge and dc bus voltage level, the SC unit operation mode is automatically decided. Meanwhile, the dc bus voltage level indicates the power demand of the whole system; by regulating the dc bus voltage, the mismatch of power demand is covered by SC unit. The effectiveness of proposed method is verified by experiment prototype formed by two distributed generation and one supercapacitor unit.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.454-456
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• 2003

This paper describes a type test results of 154 kV transmission line arrester with external gap. The test was carried on surge arrester unit and line arrester with external gap, respectively. Withstand voltage test demonstrate the voltage withstand capability of the line arrester with external series gap under the dry and wet conditions. In insulation coordination test external series gap shall be discharged every time when lightning impulse voltage with the steepness of more than 1500 $kV/{\mu}s$ are applied under the wet condition.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.17-20
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• 2002

In this paper voltage distribution in stator windings of induction motor driven by IGBT PWM inverter is studied. To analyze the irregular voltage of stator winding, equivalent circuit model of inverter-cable-motor was proposed and high frequency parameter is computed by using finite element method (FEM). Electro-magnetic transient program (EMTP) analysis of the whole system for induction motor and PWM inverter is proposed. Induction motor, 50[HP], and a switching surge generator was built to consider the voltage distribution. The results of EMTP analysis compared with experimental results.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.178-181
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• 2005

This paper presents a synchronous rectifier in a LLC half bridge topology. The proposed synchronous rectifier is used to a current driven synchronous rectifier(SR). If FET is driven without dead times. Voltage driven synchronous rectifier may introduce voltage and current surge during the zero dead times. To solve this problem, we propose to use modified current driven synchronous rectifier. Finally, the prototype is built and comparison on the current and voltage driven synchronous rectifier(SR).