• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.303-305
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• 1996

A strategy that can maximize the efficiency of the inverter system for the non-magnetic material is proposed. Frequency control and variable DC-Link voltage control are compared and analyzed by the experimental results. The experimental results show the variable DC-Link voltage control is superior to the frequency control with respect to improve the efficiency of the inverter system. MOSFETs and IGBTs are used as switching devices and IGBTs are considerable as better switching devices for improving the efficiency of the inverter system.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.47-52
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• 2016

This paper describes the design and fabrication of high frequency ground impedance measuring system for assessment of grounding system for Lightning protection. The ground impedance measuring system has been designed and fabricated which makes it possible to assess the ground impedance by frequency ranges from 100 Hz to 1 MHz. The effective grounding systems having a very low impedance to electromagnetic disturbance such as lightning surges and noises in microelectronics and high-technology branches are strongly required. In order to analyze the dynamic characteristic of grounding system impedances in lightning and surge protection grounding systems, it is highly desirable to assess the ground impedances as a measure of performance of grounding system in which lightning and switching surge currents with fast rise time and high frequency flow. The measuring system is based on the variable frequency power supply and consists of signal circuit part, main control part, data acquisition and processing unit, and voltage and current probe system. The ground impedance measuring system can be used to assess grounding system during occurrence of lightning.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.4
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• pp.582-588
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• 2002

This paper presents a efficient sensorless driving strategy for brushless dc motor(BLDCM). By varying PWM switching frequency(4KHz, 6KHz, 8KHz) properly according to the rotating speed, the improvement of the efficiency and the operating characteristics through the wide speed are obtained.. The experimental results show that the proposed method can efficiently improve the sensorless driving performance for BLDCM with trapezoidal back emf.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1296-1299
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• 2001

In this paper, a simple, novel approach is proposed for a variable hysterisis band current controller which uses feedback techniques to achieve constant switching frequency with good dynamic response. The simulation result shows constant switching frequency and consequenctly the load current ripple decrease.

• Journal of Power Electronics
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• v.16 no.3
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• pp.994-1003
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• 2016

Two major obstacles in the utilization of electrical vehicles are their price and range. The collaboration of direct torque control (DTC) with induction motor (IM) is preferred for its low cost, easy implementation, and parameter independency. However, in terms of edges, the method has drawbacks, such as variable switching frequency and undesired current harmonic distortion. These drawbacks result in acoustic noise, reduced efficiency, and electromagnetic interference. A feed-forward approach for stator-flux-oriented DTC with space vector pulse-width modulation is presented in in this paper. The outcome of the proposed method is low current harmonic distortion with fixed switching frequency while preserving the torque performance and simple application feature of basic DTC. The method is applicable to existing and forthcoming IM drive systems via software adaptation. The validity of the proposed method is confirmed by simulation and experimental results.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.163-169
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• 2003

This study was carried out develope a motor power change speed device of motor by used micro- controller. This system was producted a auto-change speed device which switching frequency was 1,000MHz by used a auto- controller. It had a continuous output current such as 5A, 11A, 25A, 35A, 50A. It used a variable voltage from 9V to 18V(Maximum). We designed hardware of and software of micro-controller, we are made up of a auto cut-off function by 3.7V for detected power-loss prevention.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.55-64
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• 2007

This paper represents characteristics and design example of series loaded LCC type high frequency resonant DC-DC converter with variable parallel capacitor in the secondary side of inductive power transformer. In this converter, ZVS(zero voltage switching) technique is applied to reduce turn-off switching losses, and the applied converter used the PFM switching pattern to control output voltage. The operating characteristics of the proposed converter is analyzed using nomalized parameter such as switching frequency and load factor with varing the secondary parallel resonant capacitor. The results of analysis show the operating characteristics and design method of the proposed converter using characteristic values. And the proposed converter can be applied for the contactless power supply with linear transfer system such as dean room facilities of semiconductor and Flat Panel Display.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.270-275
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• 2012

This paper describes design of a variable-N frequency synthesizer for RF PLL with $0.13{\mu}m$ silicon CMOS technology being used as an application of the UWB system like MBOA. To get good performance of speed and noise super dynamic circuits was used, and to get variable-N division ratio MOSFET switching circuits was used. Especially to solve narrow bandwidth problem of the dynamic circuits load resistance value of unit divider block was varied. Simulation results of the designed circuit shows very fast and wide operation characteristics as 5~26GHz frequency range.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.4
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• pp.165-173
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• 2002

The goal of this paper is optimal switching angle of switched reluctance motor drive system fur maximum energy ratio. A new magnetizing method with a low-frequency increasing the energy conversion ratio that is related to the efficiency of motor is proposed. As the results, it improved the efficiency about 2[%]. And a torque ripple is also sufficiently reduced compared with that of the conventional approach. In order tn start softly regardless of large ripple torque, the profile of phase current is predicted by the ANFIS, and current control mode was adapted when it is operated under the starting speed. Variable implementations en the fields will guarantee the more practical drive system.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.103.1-103
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• 2002

In variable structure control algorithms, The control law used to realized the desired sliding mode dynamics is discontinuous on the switching manifold. However, due to imperfections in switching, such as time delays, the system trajectory chatters instead of sliding along the switching manifold. This chattering is undesirable because it may excite unmodeled high frequency dynamics in the physical system. In this paper, to overcome this drawback a self-organizing fuzzy sliding mode control algorithm using gradient descent method is proposed. The proposed method has the characteristics which are viewed in conventional VSC, e.g. insensitivity to a class of disturbance, parameter variations and uncertainties ill the sliding mode. To demonstrate its performance, the proposed control algorithm is applied to an inverted pendulum system. The results show that both alleviation of chattering and performance are achieved.