• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.8
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• pp.539-546
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• 1987

In case of operating at Variable speed the induction motor by a frequency transformer, it will cause ripples in motor torque and considerably bad effects on the machines because the output side of the frequency transformer involves a great number of harmonics. This paper Presents the methods of decreasing torque ripples in induction motor and of improving current waveform, by means of forming the waveforms of output current into multi-step waveforms similiar to sinusoid, and also by means of eliminating the harmonic components maximally, in case of operating a 18-phase multi-inverter combining 3-step current source inverter.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.506-511
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• 1996

This paper deals with an inexpensive, simple and fast Langmuir probe sweeping circuit and its application. This sweeper completes a probe trace in a 1 ms order. Futhermore, the circuit drives a maximum probe voltage of $\pm$30V and has a maximum probe current capability of a few amperes. The plasma parameters are successfully determined using the fast Langmuir probe method.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.3
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• pp.126-131
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• 2002

This paper is proposed to position and speed control of interior permanent magnet synchronous motor(IPMSM) drive without mechanical sensor. The rotor position, which is an essential component of any vector control schemes, is calculated through the instantaneous stator flux position and an estimated flux value of rotating reference frame. A closed-loop state observer is implemented to compute the speed feedback signal. The validity of the proposed sensorless scheme is confirmed by simulation and its dynamic performance is examined in detail.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.243-245
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• 2000

In general, aluminum electrolytic capacitors are used in the DC link of PWM inverters fur ac motor drives. The capacitor usually has the shortest lifetime in the system and then determines the lifetime of the inverter system. In this paper, a method of capacitor lifetime estimation is proposed by using an ESR(equivalent series resistance) model and a heat transfer model of capacitor, from which internal operating temperature is estimated. Then, the lifetime is predicted by Arrhenius's equation. A practical example is presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2127-2134
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• 2007

The simulation model has been already developed not for 7 phase but for 3 phase BLDC motor. It is necessary to develop a new simulation model of multi-phase BLDC motor including the phase delay angle especially in the high speed region. In this paper, the suitability of the proposed model is verified through the several computer simulations, and experimented results.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.452-457
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• 1998

This paper deal with problems of leakage current, shaft voltage, bearing current, and EMI, in valiable-speed AC drives. The originating mechanism is illustrated with a high-frequency equivalent circuit. Reduction methods are classified in to six categories based on the equivalent circuit. Some experimental results show that a common-mode transformer (CMT) and a common-noise canceler (ACC) can solve the problems, which have been proposed the authors.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.293-297
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• 1998

This paper presents a newly developed speed sensorless drive using RLS based on Neural Network Training Algorithm. The proposed algorithm has just the time-varying learning rate, while the wellknown back-propagation algorithm based on gradient descent has a constant learning rate. The number of iterations required by the new algorithm to converge is less than that of the back-propagation algorithm. The theoretical analysis and experimental results to verify the effectiveness of the proposed control strategy are described.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.288-289
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• 2018

In this paper, the coupled inductor scheme instead of noncoupled inductors is suggested to reduce the dimension, weight and cost of the magnetic core. The simulation results have verified the effectiveness of the flying-capacitor MMC with coupled inductors and its control method for medium-voltage induction motor drives at low-speed operation.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.104-105
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• 2019

본 논문에서는 한 대의 인버터로 두 대의 PMSM의 병렬 운전 제어를 위한 속도 제어기를 제안한다. 제안한 제어기는 파라미터 변동에 강인한 슬라이딩 모드 제어 이론에 근거한다. 제안하는 기법은 실험을 통해 그 타당성이 검증되었다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.4
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• pp.197-204
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• 1988

A simple method that estimates the torque fluctuations in induction motor driven by CSI under steady state condition is presented and that uses the phasor diagram from the modified singlephase equivalent circuit. This method is also applied to evaluate the PWM and programmed do link modulation techniques for reducing the torque pulsations. The simplified calculations are compared with the exact digital solutions from machine D-Q equation. It is noted that the torque pulsations in induction motor driven by CSI are dependent upon the load condition unlike VSI.