• Proceedings of the Korean Magnestics Society Conference
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• 1999.04a
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• pp.58-59
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• 1999

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.1
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• pp.13-19
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• 1988

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.338-342
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• 2006

This paper analyzed the power loss of transformers considering the magnetic component. For this, each winding strategy and the effect of air gap between the ferrite core have been an important variable for optimal parameter calculation. Inductors are very well known design rules to devise, but the performance of the flyback converter as a function of transformer winding strategy has not been fully developed. The transformer analysis tool used was PExpert. The influence of the insulator thickness, effect of the air gap, how the window height and variation of the capacitive value effects the coil and insulator materials are some of parameters that have been analyzed in this work. The parameter analysis is calculated to a high frequency of 48[kHz]. Therefore, the final goal of this paper was to calculate and adjust the parameters according to the method of winding array and air gap minimizing the power loss.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.744-746
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• 2002

In this paper the method to limit inrush currents for unloaded transformers is proposed by controlling the opening instant in order to predetermine the residual flux. For the purpose of verifying the performance of the proposed method the test circuit with a single phase transformer is established and the effect of the controlled method is studied. With the basis of the obtained results the controlled method for three phase transformers with a wye-delta winding is also proposed. The analysis studies using EMTP(Electro-Magnetic Transient Program) are carried out in order to reveal its effectiveness.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.11
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• pp.508-514
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• 2005

In this paper, it was investigated the characteristics of PD(partial discharge) pulse shapes in oil and the possibility of TF(Time-Frequency) analysis for the discrimination of air corona in on-site PD measurement of oil transformers. For the purpose, single and multiple discharges combined with oil discharges and air corona were generated and measured by use of artificial models through the HFPD pulse detector and the oscilloscope. PD pulse shapes were different according to the type of defects, especially including air corona- pulses. Also, through the TF analysis, data clusters could be classified each other in the TF Map, even in the case of multiple discharges. Therefore, it is known that TF analysis could be aprlied for the improvement of on-site PD measurement in oil transformers.

• Journal of Power Electronics
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• v.13 no.2
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• pp.177-185
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• 2013

This paper studies a soft switching DC/DC converter to achieve zero voltage switching (ZVS) for all switches under a wide range of load condition and input voltage. Two three-level PWM circuits with the same power switches are adopted to reduce the voltage stress of MOSFETs at $V_{in}/2$ and achieve load current sharing. Thus, the current stress and power rating of power semiconductors at the secondary side are reduced. The series-connected transformers are adopted in each three-level circuit. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve the electric isolation and power transfer from the input side to the output side. Therefore, no output inductor is needed at the secondary side. Two center-tapped rectifiers connected in parallel are used at the secondary side to achieve load current sharing. Due to the resonant behavior by the resonant inductance and resonant capacitance at the transition interval, all switches are turned on at ZVS. Experiments based on a 1kW prototype are provided to verify the performance of proposed converter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.1
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• pp.99-108
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• 2013

The high-voltage pulse generator is consist of transformers of fundamental wave and harmonic waves, and shunt capacitances. The pulse has the fundamental wave and the harmonic waves that have been increased as a series circuit by the transformers to make high voltage pulse. This paper shows that pulse generator circuit is analyzed using Miller's theorem and network theory(ABCD Matrix) and simulated in frequency and time domain using Matlab program. The output voltage of pulse were obtained to 2.5kHz, 1.8kV. Output pulse voltage increases as $L_m$ increases in low voltage circuit. In high voltage circuit, outer capacitors are related to frequency band pass characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.60-64
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• 2020

In this study, to develop angle ring pressboards for high voltage transformers, the radius and thickness are modified under the conditions of temperature and humidity. In particular, a pressboard with a thickness of 6 mm and a radius at the angled part were investigated based on the simulation of the principal stress from the angled optimization profile shape. As a result, by the appropriate application of a higher temperature, the solid insulation can be improved to reduce the moisture content for an optimized profile angle of a high voltage transformer. This also results in the improvement of the safety factor by 25%. It is determined that the electrical insulation properties of pressboards in high voltage transformers can be enhanced by improving their properties.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.327-331
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• 2007

Inundation of substation and underground power equipment(pad-mounted transformers & switches) breaks out every summer season in low-lying downtown and low-lying shore by localized heavy rain, typhoon and tidal wave. In case inundation of substation and underground power equipment, it occurs a great economic loss owing to recovery time and events of electric shock occur by inundation electrical facility. So we search the damage situation and installation situations. Therefore we propose the necessity of protection of flood at low-lying downtown and low-tying shore. This paper will be used to present a reform proposal of electrical related law about flood protection of existing power equipment.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.241-243
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• 2006

This paper describes experimental analysis of UPQC, which is composed of cascaded H-bridges and single-phase multi-winding transformers. The operational characteristic was analyzed through experimental works with a scaled model, and simulations with PSCAD/EMTDC. The UPQC proposed in this paper can be directly connected to the distribution line without series injection transformers. It has flexibility to expand the operation voltage by increasing the number of H-bridge modules. The analysis results can be utilized to design the actual UPQC system applicable for the actual distribution system.