• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.3
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• pp.216-223
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• 2006

The high efficiency full-bridge LLC resonant converter using a contact-less transformer Is proposed for the photovoltaic power generation system. For the series resonance with a series capacitor, the LLC resonant converter utilizes the leakage inductance and magnetizing inductance of a contact-less transformer Unlike the conventional series resonant converter operated to the continuous resonant current at above resonance frequency, the proposed converter operates to the discontinuous resonant current at the narrow frequency control range below resonance frequency. Due to the discontinuous mode resonant current, the proposed converter can be achieved the zero voltage switching (ZVS) in the primary switches and the zero current switching (ZCS) in the secondary rectification diodes without my auxiliary circuit. In this paper, the experimental results of the proposed full-bridge LLC resonant converter using a contact-less transformer are verified on the simulation based on the theoretical analysis and the 150W experimental prototype.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.140-145
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• 2004

In this study, the design and analysis of a butterfly valve disk was performed to minimize the rubbing between the disk and the seat at opening and closing. The butterfly valve has double eccentric structure and the contact surface between the disk and the seat is a conical surface. At the instant of opening and closing the valve by the rotation of disk, the positions of zero contact point are changed. Also, if the cone surface is cut in the perpendicular direction to the rotation axis of the valve, the contour of cutting section is hyperbolic. Therefore minimum distance between the origin of the eccentric axis and the hyperbolic curve goes to the position of zero contact point. In order to consider the interferences between the disk and the seat, the thermal-structure coupled field analysis was performed by ANSYS.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.2
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• pp.67-73
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• 1984

The Author researched and published its results on how effectively the arcs suppressed when the contactors are opened at current zero point which indispensively exsists in AC circuits. In order to increase the effectiveness of suppressing the arcs in larger current, the author suggests a new suppressing method using auxiliary contactor which contains resistance which is connected in parallel with main contactor. The author's firm belief is that the arcs are suppressed remarkably, but there are several problems, especially how to determine the optimal resistance connected in series with auxiliary contactor.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.347-350
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• 2006

The high efficiency full-bridge LLC resonant converter using a contact-less transformer is proposed for the photovoltaic power generation system. For the series resonance with a series capacitor, the LLC resonant converter utilizes the leakage inductance and magnetizing inductance of a contact-less transformer. Unlike the conventional series resonant converter operated to the continuous resonant current at above resonance frequency, the proposed converter operates to the discontinuous resonant current at the narrow frequency control range below resonance frequency. Due to the discontinuous mode resonant current, the proposed converter can be achieved the zero voltage switching (ZVS) in the primary switches and the zero current switching (ZCS) in the secondary rectification diodes without any auxiliary circuit. In this paper, the experimental results of the proposed full-bridge LLC resonant converter using a contact-less transfonner are verified on the simulation based on the theoretical analysis and the 150W experimental prototype.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.251-258
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• 2012

The conventional network security solutions for manufacturing or factory automation devices are concentrated on protecting the internal networks from the attacks of external networks. Recently, however, so called Day-zero attacks are increased; the threat from internal devices such as notebooks, USB devices are as critical as attacks from external networks. Thus a new security solution is needed to protect manufacturing devices from both external and internal threat. To this purpose, we propose an edge-security system to provide cost effective, integrated, and simple end-point security solution specialized for automated manufacturing devices, which may avoid the shortcomings of NAC.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.31-39
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• 2012

In this paper, we propose a microprocessor-based automatic voltage regulator(AVR) to reduce consumers' electric energy consumption and to help controlling peak demanding power. Hybrid Switching Automatic Voltage Regulator (HS-AVR) consist of a toroidal core, several tap control switches, display and command control parts. The coil forms an autotransformer which has a serial main winding and four parallel auxiliary windings. It controls the output voltage by changing the combination of the coils and the switches. Relays are adopted as the link switches of the coils to minimize the loss. To make connecting and disconnecting time accurate, relays of the circuit have parallel TRIACs. A software phase locked loop(PLL) has been used to synchronize the timings of the switches to the voltage waveform. The software PLL informs the input voltage zero-crossing and positive/negative peak timing. The traditional voltage transformers and AVRs have a disadvantage of having a large mandatory capacity to accommodate maximum inrush current to avoid the switch contact damage. But we propose a suitable AVR for every purpose in smart grid with reduced size and increased efficiency.