• Journal of the Semiconductor & Display Technology
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• v.4 no.2 s.11
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• pp.11-14
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• 2005

In plasma processing reactors, it is common practice to control plasma density and ion bombardment energy by manipulating excitation voltage and frequency. In this paper, a dually excited capacitively coupled rf plasma reactor is self-consistently simulated with a three moment model. Effects of phase differences between primary and secondary voltage waves, simultaneously modulated at various combinations of commensurate frequencies, on plasma properties are investigated. The simulation results show that plasma potential and density as well as primary self-dc bias are nearly unaffected by the phase lag between the primary and the secondary voltage waves. The results also show that, with the secondary frequency substantially lower than the primary frequency, secondary self·do bias remains constant regardless of the phase lag. As the secondary frequency approaches to the primary frequency, however, the secondary self-dc bias becomes greatly altered by the phase lag, and so does the ion bombardment energy at the secondary electrode. These results demonstrate that ion bombardment energy can be more carefully controlled through plasma simulation.

• Journal of Power Electronics
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• v.14 no.4
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• pp.796-805
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• 2014

A digital controller with a low-power approach for point-of-load synchronous buck converters is discussed and compared with its analog counterpart to confirm its feasibility for system integration. The tri-mode digital controller IC in $0.35{\mu}m$ CMOS process is presented to demonstrate solutions that include a PID, quarter PID, and robust RST compensators. These compensators address the steady-state, stand-by, and transient modes according to the system operating point. An idle-tone free condition for ${\Sigma}-{\Delta}$ DPWM reduces the inherent tone noise under DC-excitation. Compared with that of the traditional approach, this condition generates a quasi-pure modulation signal. Experimental results verify the closed-loop performances and confirm the power-saving mechanism of the proposed controller.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.144-151
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• 2013

This paper presents a result of the mechanical noise and vibration analysis as well as the electrical characteristics analysis of the permanent magnet(PM) motor according to the driving method that is Brushless DC(BLDC) drive and Brushless AC(BLAC) drive. To do that, the characteristics of the PM motor, which have the same output power but different driving method, are investigated. At that time, the characteristics such as torque, torque ripple and flux density, and so on, are obtained by finite element analysis(FEA). Besides, noise and vibration are obtained by spectrum analysis. The magnetic noise is defined as noise generated from vibrations due to electromagnetic excitation force. In this paper, the electromagnetic excitation force is analyzed and design process of noise reduction is proposed. Finally, The validity of the analysis results is verified by test.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.990-992
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• 2002

30kW electrical power conversion system is delveloped for the variable speed wind turbine system. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and frequency of generator output vary according to the wind speed, a dc/dc boosting chopper is utilized to maintain constant dc link voltage. Grid connection type PWM inverter supply currents into the utility line by regulating the dc link voltage. The active power is controlled by q-axis current which the reactive power can be controlled by d-axis current reference change. The phase angle of utility voltage is detected using s/w PLL(Phased Locked Loop) in d-q synchronous reference frame. This scheme gives a low cost power solution for variable speed WECS.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.659-662
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• 2003

This paper analyzes the electro-mechanical characteristics of the spindle motor in a computer hard disk drive due to the trapezoidal and sinusoidal driving methods. The driving circuit equation is modified by considering the switching action of PWM inverter, and is coupled with the Maxwell equation for the analysis of the magnetic field. Mechanical motion of a rotor is calculated by solving Newton-Euler equation. Electro-mechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.623-630
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• 2010

This paper presents the implementation and characteristic analysis of a drive system for a three-phase permanent magnet motor with independent excitation winding that is applicable for electric bicycles. The design features improves the phase current waveform, output power, and torque by using advance angle control. This adjusts the phase angle of each phase current in relation to back EMF. In addition, a DC-side PI current control is performed through PWM generation circuit using a low-cost one-chip microcontroller and a CPLD chip, resulting in reduced system costs. Finally, the validity of this control scheme for driving electric bicycles and output/torque improvement characteristics are verified through analysis and experimental results.

• Journal of Power Electronics
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• v.10 no.4
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• pp.388-395
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• 2010

An active boost converter for a single phase SRM using series-parallel connected capacitors is proposed in this paper. The proposed active boost converter has two diodes and one power switch with an anti-parallel diode and one additional boost capacitor. The additional boost capacitor could be series or parallel connected to the dc-link capacitor to produce proper excitation and demagnetization voltage. The proposed active boost converter can easily achieve a fast excitation and demagnetization from the capacitor connection. In this paper, series and parallel connected converters are reviewed, and the detailed operating modes as well as the voltage characteristics of the proposed converter are analyzed. The simulation and experimental results shows the effectiveness of the proposed active boost converter.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.10
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• pp.151-157
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• 1997

Switched relutance motor(SRM) has the advantages of simple structure, low rotor intertia, and high power rate per unit volume. However, SRM has the disadvantages of high current harmonics, and low power factor because of the discontinuous excitation of pulse type. The harmonics brings about the distortion and loss of power system, and brings about the incorrect opertion of electronic system. This paper investigates the SRM drive system with the reduced harmonics and improved power factor. The system consists of the switching power converter with poewr factor correction(SPC-PFC), DC/DC converter and 3-phase inverter. The performances in the proposed system are verified through the simpuation and experiment.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.831-838
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• 2001

Torque ripple control of brushless DC motor has long been the main issue of the servo drive systems in which the speed fluctuation, vibration and acoustic noise need to be minimized. The vast majority of the methods for suppressing the torque ripple require the Fourier series analysis and either the iterative or least mean square minimization. In this paper, a novel approach based on the d-q-0 reference frame that achieves ripple-free torque control with maximum efficiency is presented. The proposed method optimizes the reference phase current waveforms including even the case of 3-phase unbalanced condition, and the motor winding currents are controlled to track the optimized current waveforms by the delta modulation technique. As a results, the proposed approach provides a simple and yet effectine means for obtaining the optimal motor excitation currents. The validity and applicability of the proposed control scheme are verified through simulations and experimental investigations.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.879-880
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• 2008

At the high speed operation, the boost negative bias can reduce the negative torque and increase the dwell angle, so the output power and efficiency can be improved. In this paper, a novel power converter for single phase SRM with boost negative bias is proposed. A simple passive capacitor circuit is added in the front-end, which consists of three diodes and one capacitor. Based on this passive capacitor network, the two capacitors can be connected in series and parallel in different condition. In proposed converter, the phase winding of SRM obtains general dc-link voltage in excitation mode and the double dc-link voltage in demagnetization mode. The operation modes of the proposed converter are analyzed in detail. Some computer simulation and experimental results are done to verify the performance of proposed converter.