• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.18-22
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• 2000

The partial discharge testing is widely used in insulation property measurement because it gives low stress to high voltage equipment which is undertaken tests. Therefore it is very useful method compare to previous destructive methods and effective diagnosis method in power transformer that requires live-line diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.29-32
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• 2000

The partial discharge testing is widely used in insulation property measurement because it gives low stress to high voltage equipment which is undertaken tests. Therefore it is very useful method compare to previous destructive methods and effective diagnosis method in power transformer that requires on-line & on-site diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and PD/HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.833-836
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• 1993

A flyback type power converter circuit for switched reluctance motor drives is presented. In this converter circuit, the energy extracted from an off going phase is stored in an additional capacitor. The energy stored is used to either be returned to the source frequently or energize the conducting phase during the conduction interval through the transformer. The additional switch to pass the energy stored in the capacitor to the source or the conducting phase is switched under a relatively low voltage condition. Its switching frequency is relatively high so that the size of the transformer can be reduced. The design guideline for the capacitor and the transformer is described. The effectiveness of the presented converter circuit is compared to other circuits through the analysis and experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.37-46
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• 2013

This paper proposes the boost type bidirectional zero current switching(ZCS) DC/DC converter of transformer series construction for electric vehicle operation using low voltage battery. This converter can high boost through the double voltage circuit and series construction of output part using two converters. This converter system has the advantages that bidirectional power transfer is excellent, size and making of transformer because of this converter keeps the transformation ratio to 1:1. Proposed DC/DC converter uses the ZCS method to decrease the switching loss. By replacing reactance ingredients of L-C resonance circuit for ZCS with leakage inductance ingredients of high frequency transformer and half-bridge capacitor it reduces system size and expense because of not add special reactor. It can confirm to output of high voltage to operate the electric vehicle with low voltage of input and operation of ZCS in all load region through the result of PSIM simulation and experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.401-401
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• 2009

Recently, demands for the development of compact, lightweight power supplies with higher power density and higher efficiency have been increased. Since Piezoelectric Transformer (PT) was emerged in device and material industry, it has been suggested as a viable alternative to the magnetic transformer in some applications. PT has some advantages such as low profile and mechanical energy transfer with little electromagnetic interface (EMI). Also, PT can provide high voltage stepping ratio with good isolation and requires no copper windings saving copper usage especially for large voltage conversion differences. Conventional control of PT converter has mainly two-way. One is the pulse frequency modulation (PFM) control method and the other is the pulse width modulation (PWM) control with frequency fixed method. It is known that the maximum PT efficiency can be obtained when it operates near the resonant frequency of the PT. And, also PT's resonant frequency moves according to the load condition. Therefore, selection of PT converter control method is very difficult. This paper analyzes general piezo-electric converter modeling and proposes a guide-line to selection of control method and stabilization control.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.34-39
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• 2002

Most X-ray generator had been used do rectifier type transformer high tension generator which is supplied in a clinical diagnosis. But it is difficult to miniaturize and become light weight. Also, because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. Therefore, it is supplied gradually from abroad being developed high tension generator for inverter type X-ray generator which use semi-conductor switching element for electric power that have high speed switching ability to solved these problem. But, semi-conductor element of big capacity are used by X-ray tube's big consumption power and diffusion is difficult in the small size hospital because production cost is ascending by doing digital control through DSP and product price becomes expensive. Therefore, in this paper, design and manufactured CR type voltage divider for feedback control of tube voltage of high frequency resonance type inverter and high tension transformer for high frequency to apply economical diffusion type X-ray generator which have wide output voltage and load extent. It is Proved do X-ray generator and stability of X-ray tube's output characteristics through an experiment.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.158-164
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• 2016

In this paper, a high frequency flyback type zero voltage soft switching PWM DC-DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of active power switches and a flyback high frequency transformer. In addition to these, passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three winding auxiliary high frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC-DC converter from an experimental point of view and the comparative electromagnetic conduction and radiation noise characteristics of both DC-DC power converter circuits are also depicted.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1071-1079
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• 2007

In this paper, a novel space vector control method for isolated multi-level inverter using 3-phase low frequency transformers is proposed. This method is based on the simplification of the space-vector diagram of a five-level inverter using calculated table into fully programming method. The execution time of the proposed method is about same as that of the method using calculated table. Also, the proposed method is easily applied to other case level inverter. We applied this method into the 3-phase IHCML inverter using common arm. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformers could be reduced compare with an exiting 3-phase multi-level inverter using single phase transformer. In addition, this method generates very low harmonic distortion operation with nearly fundamental switching frequency. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.107-108
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• 2016

Solid State Transformer(SST) has been recently regarded as a good alternative to conventional low frequency transformer. SST is consist of several high voltage power stage, so it is important to select optimal semiconductor switches for specification. This paper presents optimal IGBT switches for low switching losses using analyzing switching characteristics of several high voltage IGBT switches. Double Pulse Tester(DPT) experiment is used to verify characteristics of this IGBT switches.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.913-919
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• 1999

A systematic synthesis process is presented for the design of ADSL POTS splitters. It consists of a low-pass filter formed by a single-ended inductor, balanced inductor, and balance tightly coupled transformer. This three low-pass filters has been simulation. Simulation results show agreement of frequency characteristics. Therefore, POTS splitters using a commercial balance tightly coupled transformer are designed for the applications of ADSL system. The experimental results show that POTS splitter in the ADSL system has ripple decibel of less than $\pm$0.5 dB over a frequency range from 0.2 kHz to 3.4 kHz(or an audio band frequency) and delay distortion of less than 130 $mutextrm{s}$ over a frequency range from 0.6 kHz to 3.2 kHz.