• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.544-547
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• 2002

In a high power laboratory, artificial lines are used for SLF tests of circuit breakers. The line side PTRV is affected by the stray capacitances of testing and measuring equipment as well as the circuit parameters of artificial lines. The changing pattern of PTRV was examined, and the circuit parameters of artificial line for some examples were compensated using the changing pattern to satisfy test conditions specified.

• Journal of Magnetics
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• v.16 no.4
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• pp.386-390
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• 2011

This paper deals with the magnetic equivalent circuit modeling and permanent magnet (PM) performance evaluations of a pole changing memory motor (PCMM). We use a coupled transient finite element method (FEM) and Preisach modeling, which is presented to analyze the magnetic characteristics of the permanent magnets. The focus of this paper is on the evaluation of characteristics such as the magnetizing direction and the pole number of the machine under re- and de-magnetization conditions.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.111-117
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• 1998

This paper presents a polarity changing method without dead time of a cycloconverter with an LC resonant circuit. According to the proposed method, dead time to prevent short circuit for the polarity changing is not required. Therefore the delay of control and the harmonic components of output currents can be decreased. And the proposed method can be expanded for the other natural commutated cycloconverters of noncirculating current type. In this paper, the switching method of the proposed polarity changing without dead time is studied, and in order to confirm the validity of the proposed method the experiment is carried out with a cycloconverter with an LC resonant circuit.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.6
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• pp.16-23
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• 2003

In this paper, we propose an efficient bias circuit of discrete BJT component for hearing aid. The collector feedback bias circuit, widely used for the hearing aid, has a resistor for negative feedback. As the resistor affects AC and DC simultaneously, it is quite difficult to adjust amplifier gain without changing DC bias point. The previous bias circuit also has weak point to be oscillated by the positive feedback of power noise if gain of hearing aid is high. In the proposed circuit, we can reduce the two weak points of the previous circuit by adding a resistor to the collector feedback bias circuit between base and power supply which is $\beta$ times target than the collector resistor. Thus. we can change amplifier gain without changing DC bias point, and reduce power noise gain about 18.5% compare to that of tile previous circuit in the simulation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.6
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• pp.267-272
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• 2002

This Paper deals with the short circuit tests of the three-Phase DC reactor type fault current limiter (FCL) in changing of turns ratio of transformers. The experiment of this paper is a preliminary step to develop the FCL's faculties for an application to high voltage transmission line. So, superconducting coil was made of Nb-Ti, low temperature superconductor, and the ratings of the power system of experimental circuit are 400V/7A class. A three-phase DC reactor type FCL consists of three transformers, six diodes, one superconducting coil and one cryostat. The important point of experimental analysis is transient period, the operating lagging time of circuit breaker. As the results of the experiment, the values are referred to the limitation rate about 77% and 90% when the turns ratio of transformer was 1:1 and 2:1 respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.9 no.1
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• pp.61-73
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• 1985

The induction motor is widely used in the power equipments of the ship and the various industrial drive applications because it is robust and relatively simple and cheap to manufacture, but it has a disadvantage that the speed of induction motor is not controlled in wide range such as d.c motor. In this paper, the characteristics relating to the Kramer system that the speed of three phase wound type induction motor is controlled by changing the exciting e.m.f. of the secondary circuit is described. In order to analyze the characteristics, a new simplified and approximated T-type equivalent circuit from the Kramer circuit with three phase graetz connection and d.c machine is proposed. The stator current, motor torque and mechanical output power are computed by the current, torque and power equations derived by its equivalent circuit. Through the experiments, the $I_f-N$, torque-slip and current-slip characteristic curves of the tested motor are obtained and the various needed constants are determined. The numerical values obtained from the above method are compared with experimental values under the same conditions. As a result of the above investigation, it is found that the induction motor speed by the Kramer system is controlled by 28 per cent under the rated speed by changing the field current of d.c motor and the values computed by the current and torque equations derived by the simplified and approximated T-type equivalent circuit generally come to approach the experimental values.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.235-240
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• 2002

In micro-EBM, it is well blown that RC circuit is suitable for discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, if very low, continuous (or normal) arc discharge occurs, then increases electrode wear and reduces machining speed remarkably. In this paper, RC circuit with transistor is used to micro-EDM. Experimental results show that RC circuit with transistor can cut off continuous (or normal) arc discharge effectively if duty factor and switching period of transistor are set up optimally. Through experiments with varying charge resistance, it can be known that RC circuit with transistor has about two times faster machining speed than that of RC circuit. Especially, it has prominent rise-effect of machining speed in low unit discharge energy, so that a high-quality and high-speed micro-EDM can be realized through RC circuit with transistor.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.44-51
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• 2004

In a micro-EDM, it is well known that an RC circuit is suitable as a discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, when the resistance is very low, continuous (or normal) arc discharge occurs, electrode wear increases and machining speed is reduced remarkably. In this paper, an RC circuit with transistors is used in a micro-EDM. Experimental results show that the RC circuit with transistors can cut off a continuous (o. normal) arc discharge effectively if the duty factor and switching period of the transistor are set up optimally. Through experiments with varying charge resistances, it is shown that the RC circuit with transistors has about two times faster machining speed than that of an RC circuit.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.12
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• pp.868-873
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• 1987

In this pater, we have proposed a synthetic main chopper circuit for the chopper controlled electric automobile. The proposed chopper circuit operates as a step-down chopper in powering mode and as a polarity reversion type chopper in regenerative braking mode. In this study, it was found that powering and regenerative braking operations using the separately excited D.C motor can be controlled continuously only by gate signals of the chopper without changing the connection of the circuit.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.99.2-99
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• 2001

An electronically tunable current-mode second-order multifunctional filter is described in this paper. The proposed filter consists of two four-terminal floating nullors (FTFNs), two dual-output OTAs and two grounded capacitors. The circuit can simultaneously realize the lowpass, bandpass and highpass current transfer functions from the same configuration without changing the circuit configuration and elements. The natural angular frequency we and the parameter wo/Q can be orthogonally controlled through adjusting the transconductance gain of OTA. PSPICE simulation results are employed to confirm the circuit performance.