• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1581-1583
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• 1999

Epoxy Compound has been used as insulation material in cable accessories. During the applying voltage to cable, heat shock is induced to accessory by the temperature difference between atmosphere and conductor. In this study, crack resistance, thermal and mechanical properties were evaluated about conventional epoxy compound and rubber toughened epoxy compound. Because rubber absorbs the stress caused by heat shock, crack resistance of rubber toughened epoxy compound is high. In the case of low thermal expansion coefficient, the compound shows high crack resistance because of low volumetric change.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.778-783
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• 2012

The synthetic short-circuit making test to adequately stress the circuit breaker has been specified as the mandatory test duty in the IEC 62271-100. The purpose of this test is to give the maximum pre-arcing energy during making operation. And this requires the making operation with symmetrical short-circuit current that is established when the breakdown between contact gap occurs near the crest of the applied voltage. Also, if the interrupting chamber of circuit breakers is designed as the type of common enclosure or the operation is made by the gang operated mechanism that three-phase contacts are operated by one common mechanism, three-phase synthetic making test is basically required. Therefore, several testing laboratories have developed and proposed their own test circuits to properly evaluate the breaker performance. With these technical backgrounds, we have developed the new alternative three-phase making circuit.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.376-379
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• 2000

This paper presents an improved ZVS partial series resonant DC/DC converter (PSRC) with low conduction losses suitable for high power and high frequency applications. The proposed PSRC have advantages of zero-voltage-swiching (ZVS) of main switches for entire load ranges and low conduction losses of main switches by decreasing current stresses Also the reduction of the effective duty cycle is not occurred during the resonant period of the main circuit because the auxiliary circuit of the proposed converter is placed out of the main power path. An improved ZVS PSRC has a so much characteristics with respect to the reduction of current stress. The operation principles of the proposed converter are explained in detail and the various simulated and experimental results show the validity of the proposed converter.

• Journal of Power Electronics
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• 제9권6호
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• pp.929-939
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• 2009

This paper presents a new soft-switching boost converter based on the LC resonance and passive clamping technique without additional active switches. The circuit achieves high efficiency and low voltage stress by adopting a soft switching method using LC resonance. This paper gives a mathematical analysis of each mode and a detailed design procedure of the proposed boost converter. First of all, the operational principles are verified through simulation results. Then, according to the design procedure, we designed and built a 1.5[kW] prototype soft switching boost converter. Through the experimental results, we demonstrated the validity and usefulness of the proposed boost converter.

• Transactions on Electrical and Electronic Materials
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• 제11권5호
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• pp.216-221
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• 2010

The microstructure, electrical properties, and DC-accelerated aging behavior of the Zn-Pr-Co-Cr-Y-Er (ZPCC-YE) varistors were investigated for different amounts of erbium oxide ($Er_2O_3$). The microstructure consisted of zinc oxide grain and an intergranular layer ($Pr_6O_{11}$, $Y_2O_3$, and $Er_2O_3$-rich phase) as a secondary phase. The increase of $Er_2O_3$ amount decreased the average grain size and increased the sintered density. As the $Er_2O_3$ amount increased, the breakdown field increased from 5094 V/cm to 6966 V/cm and the nonlinear coefficient increased from 27.8 to 45.1. The ZPCC-YE varistors added with 0.5 to 1.0 mol% $Er_2O_3$ are appropriate for high voltage, with high nonlinearity and stability against DC-accelerated aging stress.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권4호
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• pp.257-263
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• 2006

New charge pump circuits with low area and high power efficiency are proposed and verified in this paper. These pump circuits do not suffer the voltage stress higher than $V_{DD}$ across their pumping capacitors. Thus they can use the thin-oxide MOSFETs as the pumping capacitors. Using the thin-oxide capacitors can reduce the area of charge pumps greatly while keeping their driving capability. Comparing the new pump (NCP-2) with the conventional pump circuit using the thick-oxide capacitors shows that the power efficiency of NCP-2 is the same with the conventional one but the area efficiency of NCP-2 is improved as much as 71.8% over the conventional one, when the $V_{PP}/V_{DD}$ ratio is 3.5 and $V_{DD}$=1.8V.

• Journal of Electrical Engineering and Technology
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• 제6권3호
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• pp.369-374
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• 2011

An induction motor operated with high voltage source generally generates high current in starting mode and has a long transient time after being started. This large and sustaining starting current causes the end windings of the stator to have excessive electromagnetic force. This force is the source of vibration and has a negative and serious influence on the insulation of end windings. Therefore, designing the end winding part with an appropriate support system is needed. To design the support ring enclosing the end windings, we analyze the distribution of electromagnetic force on the end windings by applying the Biot-Savart's law and the 3D finite element method (FEM), and comparing two simulation methods. Finally, we verify the safety of the support structure of the end winding part using stress analysis, which is analyzed with the electromagnetic forces from the 3D FEM simulation.

• 한국전기전자재료학회논문지
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• 제16권10호
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• pp.946-951
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• 2003

A high-Tc superconducting cable(HTS cable) is expected as an underground power line supplying the electrical power the densely populated city in future. The electrical insulation is very important for develop HTS cable system because it is operated a high voltage and in cryogenic temperature. We manufactured a mini-model cable and measured a tan$\delta$ of cable using schering bridge. The tan$\delta$ of PPLP was lower than that of Tyvek and Kraft at a given temperature, the tan$\delta$ of PPLP was 1.16${\times}$10-3. According to the increase of electric stress the tan$\delta$ increased because partial discharge occurred inside butt gap of mini-model cable. However, the tan$\delta$ decreased by increase of liquid nitrogen pressure. This reason is thought by decrease of part discharge between butt gap by increase of liquid nitrogen pressure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1075-1077
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• 1999

XLPE cables are being used more widely all over the world as extra-high voltage transmission lines owing to the superior characteristics compared to OF cables. In view of the worldwide trend of utilizing high stress cables, we developed the accessories for 230kV XLPE cables which have smaller insulation thickness than that of present cables. The performance of the newly developed 230kV cable and its accessories has superior inital characteristics. As a result, the improved reliability of 230kV XLPE cable system has been obtained. This paper describes the major design concept and the test results of development procedure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집
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• pp.19-22
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• 2004

Growth of Electrical Tree Under 50Hz~60Hz high electric stress has been studied on the Occurrence of a Pattern, to the Progression Speed at Y axis of electrical Tree. CCD Images of evolving tree structures could be obtained in both systems. Electrical Treeing was found to occur reproducibly, but in a markedly different manner in the two morphologimlly different but chemically identical materials. For the measurement of Electrical Tree, a visual measurement with an optical microscope has been used to explain breakdown mechanism in High-voltage systems.