• Journal of Power Electronics
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• v.17 no.3
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• pp.798-810
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• 2017

This paper presents a combined system of a small-capacity inverter and multigroup delta-connected thyristor switched capacitors (TSCs). The system is referred to as a hybrid static compensator (HSC) and has the functions of dynamic reactive power compensation and harmonic suppression. In the proposed topology, the load reactive power is mainly compensated by the TSCs. Meanwhile the inverter is meant to cooperate with TSCs to achieve continuous reactive power compensation, and to filter the harmonics generated by nonlinear loads and the TSCs. First, the structure and mathematical model of the HSC are discussed Then the control method of the HSC is presented. An improved reduced order generalized integrator (ROGI)-based selective current control method is adopted in the inverter to achieve high-performance reactive and harmonic current compensation. Meanwhile, a switch control strategy is proposed to implement precise and fast switching of the TSCs and to avoid changing the time delay needed by the conventional switch strategy. Experiments are implemented on a 20 KVA HSC prototype and the obtained results verify the validity of the proposed HSC system.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.531-533
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• 1996

The most common method of the single phase induction motor(SPIM) is to install a starting condenser and a centrifugal switch in series with the auxiliary winding. Even though this capacitor start method is embodied simply, it is feasible because of motor failure from malfunction of the centrifugal switch and the starting condenser. Moreover, it is hard to improve the performance characteristics of the SPIM. In this paper, the voltage and phase angle sequence, control strategy of the auxiliary winding of the SFIM is employed to eliminate the centrifugal switch and the starting condenser. The proposed control system is superior to a conventional system in the starting performance of SPIM. Finally, the improved starting characteristics of the SPIM is obtained with this strategy through simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.149-152
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• 2001

A Single-phase bi-directional inverter Using a diode bridge-type resonant circuit to implement ZVT(Zero Voltage Transition) switching is Presented. It is shown that the ZACE(Zero Average Current Error) algorithm based polarized ramptime current control can provide a suitable interface between diode bridge-type resonant circuit DC link and the inverter. The current control algorithm is analyzed about how to design the circuit with analyzed switch which m ZVT operation for the main power switch The simulation and experimental results would be shown to verify the proposed current algorithm, because the main power switch is turn on with ZVT and the bi-directional inverter is operated.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.644-651
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• 2001

The purpose of this study is to develop the improvement method of MOV(Motor Operated Valve) operability without major modification or change of MOV which needs a great expense and manpower. We studied valve stem lubrication, stem packing thrust and actuator control switch which could give an major effect to MOV operability, and found the some consequences. First, the stem/stem-nut friction coefficient and stem factor is significantly effected by stem lubrication state. Second, the measured packing thrust value is appeared higer than the design value for tested valves and the preparation of optimal value selection criteria is needed. Finally, optimization of MOV control switch is another major factor for MOV operability and structual integrity.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.668-676
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• 1998

A passive energy recovery snubber for high-power-factor boost rectifier, in which the main switch is described in terms of the equivalent circuits that are operational during turn-on and turn-off sequences. These equivalent circuits are analyzed so that the overshoot voltage across the main switch, the snubber current, and the turn-off transition time can be predicted analytically. The main switch combined with proposed snubber can be turned on with zero current and turned off at limited voltage stress. The high-power-factor boost rectifier with proposed snubber is implemented, and the experimental results are presented to confirm the validity of proposed snubber.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.722-732
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• 2018

Dual type Independent multi-phase BLDC Motor (DI-BLDCM) is designed to be robust to faulty conditions of motor and drive system. Despite the efforts of the motor design, open-switch faults of DI-BLDCM drive system cause the torque ripple of the motor. This torque ripple makes unwanted sound noise and mechanical vibration of associated systems. This paper proposes four methods for compensating the torque ripple and compares the characteristics of each proposed method. All proposed methods are able to reduce the torque ripple to similar level of the healthy condition, although the motor operates in open-switch fault conditions. However, these methods have different characteristics in various fault conditions. Therefore, from the results of the comparison, the suitable method is selected for the various fault conditions. The feasibility of the proposed methods is proved by the several experimental results.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.248-250
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• 2005

This paper suggests a new type of 4-switch inverter for switched reluctance motor drives. 4-switch Inverter topology is studied to provide possibility for the realization of cost of 3-phase SRM drive system. We used Y-connection and two-phase exciting method. For effective utilization of the developed system, a direct current controlled PWM scheme is designed and implemented to produce the desired dynamic. We solve to balance the neutral point of Y-connection by the direct current controlled PWM and examine the performance of proposed system. With the algorithm and developed control scheme, is expected that the proposed system can be widely used in commercial applications with a reduced system cost.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.117-125
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• 2016

In this paper, the inverter switch losses of BLDC motor for three types of PWM methods and power devices were analyzed. When the BLDC motor is driven at low currents, the inverter switch losses for MOSFET are low because MOSFET operates like resistance. However, the inverter switch losses for IGBT are higher than MOSFET due to its large turn-off losses. Moreover, synchronous rectification switching method is adaptable because MOSFET has 2-channel. So, MOSFET can be driven with more low impedance and losses. For low power inverter with MOSFET, the power losses of unified PWM are lower than that of unipolar and bipolar PWM. Proposed method and losses analysis results are verified by examination and simulation using Matlab/Simulink.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.224-225
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• 2013

This paper describes the four switch three-phase Z-source active power filter. This novel configuration has many advantages like reduction of cost, switching loss and smaller drive circuit. The paper presents an application of direct current control(DCC) method in a three-phase parallel Z-source active power filter to reduce the harmonics generated by the nonlinear load. The compensation principles and dynamics of the system are discussed in detail. The results show that the proposed control strategy is feasible and efficient.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.4
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• pp.152-154
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• 2005

We demonstrate a simple $CO_2$ laser by controlling firing angle of a TRIAC switch in ac power line. The power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply does not need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. In order to control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of TRIAC gate is varied from $45^{circ}$ to $135^{circ}$. A ZCS(Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control the gate signal of the TRIAC precisely. The maximum laser output of 40W is obtained at a total pressure of 18 Torr, a pulse repetition rate of 60Hz, and a TRAIC gate firing angle of $90^{circ}$.