• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.643-645
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• 1999

The conventional high frequency phase-shifted full bridge dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval. Due to this circulating current, RMS current stress, conduction losses of transformer and switching devices are increased. To alleviate this problem, this paper provides a circulating current free type high frequency soft switching phase-shifted full bridge (FB) dc/dc converter with the modified energy recovery snubber (ERS) attached at the secondary side of transforemr.

• International Journal of Safety
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• v.5 no.1
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• pp.1-4
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• 2006

The safety performance of the current collection system is evaluated by conducting a test run in which accelerometer and load cell signals are analyzed. It has been found that the current collection performance is strongly influenced by the train speed, with the major frequency components arising from the train traversing the span spacing and the 8.5 Hz component originating from the panhead resonance. The train acceleration is found to have significant influence on the span passing frequency but negligible effect on the resonant response.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.220-221
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• 2002

There has been a demand for higher frequency operation of magnetic devices. Consideration of the materials that could be applicable to such high frequency applications is the first step when designing magnetic thin films for high-frequency use. Materials suitable for high frequency application should have a larger $M_{S}$ and an appropriate anisotropy field ( $H_{K}$), which increase a resonance frequency, and also a larger $\rho$, which reduces eddy current loss. (omitted)ted)

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.1056-1061
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• 1998

In this paper, a novel zero current switching (ZCS) high frequency inverter for induction heating is proposed. The ZCS characteristics are investigated from both the numerical analysis and the experiment.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.4
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• pp.227-233
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• 2007

In case of design of a rectifier to supply high current, To select switching frequency of semiconductor switches affect absolutely the design of the LC filter value in an power conversion circuit. The conventional rectifier by using MOSFET is no use in high current equipments because of small drain-source current. To solve this problem, this paper proposes to design of high capacity rectifier by parallel driving of MOSFET in the single half bridge DC-DC converter. This method can be able to develop high current rectifier by distributed drain-source current. The proposed scheme is able to expect a decrease in size, weight and cost of production by decreasing the LC filter value and increasing maximumly the switching frequency. The validity of the proposed parallel driving strategy is verified through computer-aided simulations and experimental results.

• Journal of Power Electronics
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• v.11 no.3
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• pp.256-263
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• 2011

This paper utilizes free oscillation and energy injection principles to generate and control the high frequency current in the primary track of a contactless power transfer system. Here the primary power inverter maintains natural resonance while ensuring near constant current magnitude in the primary track as required for multiple independent loads. Such energy injection controllers exhibit low switching frequency and achieve ZCS (Zero Current Switching) by detecting the high frequency current, thus the switching stress, power losses and EMI of the inverter are low. An example full bridge topology is investigated for a contactless power transfer system with multiple pickups. Theoretical analysis, simulation and experimental results show that the proposed system has a fast and smooth start-up transient response. The output track current is fully controllable with a sufficiently good waveform for contactless power transfer applications.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.232-238
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• 2004

The dynamic characteristics of the current collection process of the high-speed railway are investigated through signals acquired during a test run. The signals are obtained from accelerometers, load cells, and strain gauges attached to various positions of the pantograph, and they are processed in time-and frequency-domains to obtain the dynamic characteristics. The main natural frequency of the pantograph is found to be 8.5Hz. There also are components at low frequencies varying linearly with the train speed. The contact frequency components above 20Hz is attenuated as they pass through the secondary suspension. The main frequency component of the load cell signal is found to be related with the rolling motion of the panhead generated by the stagger in the catenary.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.304-308
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• 2001

This paper presents a novel prototype of ZCS-PFM high frequency series resonant inverter using IGBT power module for electromagnetic induction eddy current-heated roller in copy and printing machines. The operating principle and unique features of this voltage source half bridge inverter with two additional soft commutation inductor snubber are presented including the transformer modeling of induction heated rolling drum. This soft switching inverter can achieve stable zero current soft commutation under a discontinuous and continuous resonant load current for a widely specified power regulation processing. The experimental results and computer-aided analysis of this inverter are discussed from a practical point of view.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.4
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• pp.369-378
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• 1992

This paper proposes a utility parallel processing inverter system, which consists of a voltage source PWM inverter, isolation transformer and a reactor linking the inverter to utility line. This system realizes following functions : (1) voltage phase frequency and amplitude synchronization between inverter and utility line at stand-alone mode. (2) current phase synchronization between inverter and load at parallel mode. Therefore, despite sudden increase in load current over setting point at stand-alone mode, inverter system can be transferred into parallel mode immediately without transient current. Furthermore, high frequency(18KHz) PWM control and sinusoidal filtering improve the inverter output waveform by eliminating high order harmonic components as well as low order. As a switching device, IGBT is used for high frequency switching and large current capacity.

• Journal of Power Electronics
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• v.19 no.2
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• pp.431-442
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• 2019

This paper proposes a unified high-frequency bipolar buck-boost (UHFBB) control strategy for a dual-active-bridge (DAB), which is derived from the classical buck and boost DC/DC converter. It can achieve optimized current stress of the switches and soft switching in wider range. The UHFBB control strategy includes multi-control-variables, which can be achieved according to an algorithm derived from an accurate mathematical model. The design method for the parameters, such as the transformer turns ratio and the inductance, are shown. The current stress of the switches is analyzed for selecting an optimal inductor. The analysis is verified by the experimental results within a 500W prototype.