• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.1
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• pp.14-21
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• 2004

Most adjustable-speed drives (ASDs) designed to operate low voltage induction motors incorporate voltage-source inverters (VSIs), which create motor voltages at high switching frequencies. The motor leads used to connect an ASD to a motor can behave like transmission lines for voltage pulses, which can be reflected at the motor terminals. The resulting oscillatory transient, known as the long-lead effect, can stress and consequently degrade the stator insulation system of a motor. This paper describes the results of tests to 1) determine the correlation between peak motor voltage and the length of motor leads and 2) determine the correlation between peak motor voltage and the switching frequency of the ASD Insulation failures like this usually are caused by voltage surges. Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.5
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• pp.461-466
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• 2004

In this paper, the novel patch antenna for polarization diversity using switching element is presented. The proposed antenna consists of the square patch with a pair of truncated corners and a microstrip-feed line with power divider. A switching microstrip-line feed works at schottky diode ON / OFF that is placed at $\lambda$/4 point from branch-off point of power divider. Polarization diversity has two types(LHCP. RHCP) as switching the schottky diodes. The measured 3 ㏈ axial ratio bandwidth for switching operation is about 2 %.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.916-917
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• 2008

In this paper, Switching damage of switches that is used to proposed power conversion system is reduced by soft switching way. dissipation by part resonance and my resonance stress for resonance of resonance circuit are decreased. Is acted by conversion system high effectiveness. Have following characteristic. Design snubber circuit that is used by switch protection in existent hard work rate Topology by resonant circuit for sogt switching, circuit structure was simple and control system is easy. Also, Can generate free output voltage by multi level Tuesday of output that use individuation Power Cell's Phase Shift PWM, and Low-end switching frequency the harmonic is few.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.316-319
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• 1998

RPWM(Random Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics on the wide frequency area. Using randomly changed switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise cab be spread to the wide-band area. The wide-band noise is much more comfortable and less annoying than the narrow-band one. So RPWM have been attracting an interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position PWM) is proposed and implemented. Each of three pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is executed in the C167 microcontroller also. The experimental results show that the voltage and current harmonics were spread to wide band area and that the audible switching noise was reduced by proposed RPPWM method.

• Journal of Power Electronics
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• v.11 no.1
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• pp.10-15
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• 2011

In this paper, a new soft switching three phase inverter with a quasi-resonant dc-link is presented. The proposed inverter has a dc-link switch and an auxiliary switch. The inverter switches are turned on and off under zero voltage switching condition and all auxiliary circuit switches and diodes are also soft switched. The control utilizes PWM and the auxiliary switch does not require an isolated gate drive circuit. In this paper, the operation analysis and design considerations of the proposed soft switching inverter are discussed. The presented experimental results of a realized prototype confirm the theoretical analysis.

• Journal of Power Electronics
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• v.16 no.3
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.9
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• pp.467-472
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• 2001

In conventional zero-current-switching(ZCS) PWM converters, zero-current turn-off for main switch without increasing voltage/current stresses is achieved at a fixed frequency. The switching loss, stress, and noise, however, can\`t be minimized because they adopt auxiliary switches turned off and main switches turned on under hard-switching condition. In this paper, new ZCS-PWM converters of which all switches are always operating with soft-switching condition are proposed. Therefore, the proposed ZCS-PWM converters are most suitable for systems requiring high-power density Breadboarded ZCS-PWM boost converters using power MOSFET are constructed to verify theoretical analysis.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.535-542
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• 1996

A zero voltage switching (ZVS) three level auxiliary resonant commutated pole inverter (ARCPI) is presented for high power GTO inverters. The concept of ARCP for two level inverter is extended to the three inverter. The proposed auxiliary commutation circuit consists of one resonant inductor and two bi-directional switches, which provides ZVS condition to the main devices without increasing device voltage or current stresses. The auxiliary device operates with zero current switching (ZCS) which enables use of the low cost thyristors. The proposed ARCPI can handle higher voltage and higher power (1-10MVA) comparing to the two level one. Operation and analysis of the ARCPI are illustrated and the features are compared o those of the snubber circuit incorporated three level inverter. Experimental results with 10kW, 4kHz prototype are presented to verify the principle of operation. (author). refs., figs., tab.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.453-459
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• 2001

In this paper, the loss analyses of two soft switching techniques for two-transistor forward converter are performed. The sums of snubber conduction and capacitive turn-on losses for two transistors are calculated to compare the losses of the two techniques. While the conventional soft switching technique shows the loss difference between two transistors, the proposed soft switching technique shows equal as well as lower losses In two transistors. Thus, it can be said that even thermal distribution and higher reliability can be obtained by the proposed soft switching technique.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.133-136
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• 2008

This paper presents a novel soft switching topology with resonant DC-DC converter and inverter. The resonant DC-DC converter consists of the auxiliary switch, resonant capacitor and inductor. All switches in the proposed topology is turn on at ZCS and turn off at ZVS operation. The proposed soft switching technology can be obtained the reduced switching losses and voltage and current stress of the power devices. Therefore, the resonant converter efficiency is higher than conventional boost converter. Simulation results on a 1kW soft switching converter are presented.