• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.281-285
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• 1998

The microstructure and conduction characteristics of ZnO varistor fabricated in the range of 0.0 ~ 4.0mol% $Y_20_3$ were investigated. With increasing$Y_20_3$ content, distribution of spinel phase decreased, whereas Y-rich phase segregated to the nodal point increased, as a result, the average grain size decreased in the range of $20.0 ~ 4.8{\mu}m$. $Y_20_3$ content showing relatively good conduction characteristics was l.Omol%, then nonlinear exponent and leakage current was 55.3, 0.66mA.respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1007-1010
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• 2003

We made use of $Alq_3$ which is the representative light-emitting material. Electric conduction mechanism and luminance characteristics were analyzed in this paper. We have also measured current density-thickness-voltage characteristics with thickness variation from 60 to 400nm. we analyzed the low electric and the high electric field in theoretically. Also, maximum luminous efficiency is the thickness 200 nm of $Alq_3$ in luminous-thickness characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.358-359
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• 2008

The heat generated in the high-Tc superconducting (HTS) devices is related with the cost efficiency and safe factor of HTS devices. This paper deals with the quench at the conduction-cooled joint between the HTS wire and copper terminals. The 3-D numerical simulation of this phenomenon was implemented and compared with the experimental results. The experiment was implemented with the HTS wire mounted on the copper blocks cooled with a Gifford McMahon (GM) cryocooler.

• Journal of Power Electronics
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• v.9 no.2
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• pp.275-287
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• 2009

This paper investigates analytical models of Conduction and Switching Losses (CASLs) of a matrix-Z-source converter (MZC). Two analytical models of the CASLs are obtained through the examination of operating principles for a Z-source inverter and ac-dc matrix converter respectively. Based on the two models, the analytical model of CASLs for a MZC is constructed and visualized over a range of exemplified operating- points, each of which is defined by the combination of power factor (pt) and modulation index (M). The model provides a measurable way to approximate the total losses of the MZC.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.763-765
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• 1988

Thermally stimulated current, cubical expension, capability change were measured by temperature variation. According to the capability change, TSC peak value was increased. We found that the crystal dissolution is 375 K and amorphous state becomes 388K. Charged partical behavior in the dipole and electronic trop were found iomic conduction in the low field and electronic conduction in the high field. Charged particle in the semiconduction storey was aceumulated in the interface by electron injection which can be arise TSC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.832-837
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• 2006

Antennas were fabricated by physical(adhesive) and chemical(deposition+plating) method on organic-inorganic composite material. And antennas were measured dielectric constant and gain. Dielectric constant of antennas were fabricated by physical method was decreased with increase of adhesive tape thickness and number of conduction material composition. But antennas were fabricated by chemical method was reached to 90 % of dielectric material. Gain of antennas were fabricated by physical method was decreased with increase of adhesive tape thickness. But they were unrelated with conduction material composition. The other side antennas were fabricated by chemical method excelled more 0.8 dBic than antennas were fabricated by physical method in gain of antenna. Finally, chemical method can expect excellent product process because it can produce smaller size, higher gain and elimination of many handworks.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1503-1506
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• 1997

The main fault in this interface is that power cable insulating materials are mainly composed of a double layered structure, XLPE/EPDM laminates in cable joint. In this paper, we instituted the interface of normal and degassed XLPE/EPDM and then investigated the breakdown and conduction characteristics as a function of heat treatment time. The results showed that conduction and breakdown strength was influenced by volatile crosslinking by-products which remained inside the insulating material during the production of XLPE and EPDM, especially during heat treatment process. And micro voids and surface roughness also influenced the conduction current and breakdown strength.

• Journal of Power Electronics
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• v.1 no.2
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• pp.71-77
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• 2001

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of DC to DC PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of DC to DB PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5 kW prototype converter operating at 40 kHz.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.8
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• pp.404-410
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• 2006

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 40[K] should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. In order to take advantage of a greater critical current density of high temperature superconducting (HTS) and considerably reduce the size and weight of the system, conduction-cooled HTS superconducting magnetic energy storage (SMES) at temperatures well below 40[K] should be investigated. This work focuses on the breakdown and flashover phenomenology of dielectrics exposed in air and/or vacuum for temperatures ranging from room temperature to cryogenic temperature. Firstly, we summarize the insulation factors of the magnet for the conduction cooled HTS SMES. And Secondly a surface flashover as well as volume breakdown in air and/or vacuum with two kind insulators has been investigated. Finally, we will discuss applications for the HTS SMES including aging studies on model coils exposed in vacuum at cryogenic temperature. The commercial application of many conduction-cooled HTS magnets, however, requires refrigeration at temperatures below 40[K], in order to take advantage of a greater critical current density of HTS and reduce considerably the size and weight of the system. The magnet is driven in vacuum condition. The need to reduce the size and weight of the system has led to the consideration of the vacuum as insulating media. We are studying on the insulation factors of the magnet for HTS SMES. And we experiment the spacer configure effect in the dielectric flashover characteristics. From the results, we confirm that our research established basic information in the insulation design of the magnet.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.63-72
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• 2006

The purpose of this raper is to address the negative impedance instability in DC/DC converters. We present the negative impedance instability of PWM DC/DC converters loaded by constant power loads (CPLs). An approach to design digital controllers for DC/DC converters Is presented. The proposed method, called Power Alignment control technique, is applied to DC/DC step-down choppers operating in continuous conduction or discontinuous conduction modes with CPLs. This approach uses two predefined state variables instead of conventional pulse width modulation (PWM) to regulate the output voltage. A comparator compares actual output voltage with the reference and then switches between the appropriate states. It needs few logic gates and comparators to be implemented thus, making it extremely simple and easy to develop using a low-cost application specific integrated circuit (ASIC) for converters with CPLs. Furthermore, stability of the proposed controllers using the small signal analysis as well as the second theorem of Lyapunov is verified. Finally, simulation and analytical results are presented to describe and verify the proposed technique.