• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.87-88
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• 2007

We investigated the current limiting characteristics of flux-lock type superconducting fault current limiter using YBCO films University, Gwangju health college. The flux-lock type SFCL consisted of the transformer with a primary winding and a secondary winding connected in parallel, and the superconducting element was connected with secondary winding in series or parallel. Serial and parallel connections of superconducting elements are necessary for the increase of voltage and current capacities when we intend to apply the flux-lock type SFCL.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.229-230
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• 2007

We investigated the quench characteristics of a superconducting element, two superconducting elements in order to increase the current capacity of flux lock type SFCL. The flux-lock type SFCL consisted of the transformer with a primary winding and a secondary winding connected in parallel, and the superconducting element was connected with secondary winding in series. The applied voltage at that time was 160 ${\sqrt{3}}$. We found that the parallel connection between the superconducting elements increased the power capacity and let quench characteristics improve through their mutual linkage.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.561-566
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• 2016

In this paper, effective design method of linear induction motor(LIM) for Maglev is proposed in order to maximize system efficiency of Maglev. For the high system efficiency of Maglev, it is important to minimize weight of traction motor. Light weight design by changing materials of core and winding is conducted without changing volume of LIM. For the silicon steel core of primary part for magnetic flux path, iron-cobalt alloy steel with high magnetic saturation characteristic compared to silicon steel is suggested. Moreover, aluminium winding with light weight instead of copper winding is wounded in the widen slot area due to the high magnetic saturation level. For the verification of performance of proposed model, the characteristics are analyzed by using finite element method(FEM).

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.134-141
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• 2004

This paper presents a method of synchronous rectifier(SR) for improving the efficiency in DC/DC converter. The proposed method is used push-pull topology on primary as a single winding self driven synchronous rectification(SWSDSR). Specially, this method can improve efficiency to turn on SR switch during dead time. Finally, the simulation and experimental results will be given to show comparison and analysis on the efficiency between self driven synchronous rectification(SDSR) and SWSDSR method.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.533-539
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• 2018

In this paper, the transformer type superconducting fault current limiter (SFCL) with additionally coupled circuit was suggested and its peak fault current limiting characteristics due to the fault condition to affect the fault current were analyzed through the fault current limiting tests. The suggested transformer type SFCL is basically identical to the previous transformer type SFCL except for the additional coupled circuit. The additional coupled circuit, which consists of the magnetically coupled winding to the primary and the secondary windings together with another superconducting element and is connected in parallel with the secondary winding of the transformer type SFCL, is contributed to the peak fault current limiting operation for the larger transient fault current directly after the fault occurrence. To confirm the fault current limiting operation of the suggested SFCL, the fault current limiting tests of the suggested SFCL were performed and its effective peak fault current limiting characteristics were analyzed through the analysis on the electrical equivalent circuit.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.2
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• pp.39-46
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• 2004

In this paper, the effects of roll diameter and storage time in roll form, bending method and relative humidity on curl in copy paper and inkjet coated papers are investigated. In copy paper, more MD curl is showed at smaller roll diameter and the extension of bending time. However CD curl is hardly influenced by roll diameter and bending time. At high relative humidity, especially CD curl largely reduces. All inkjet coated papers without the primary or the secondary back coating during papermaking show the increase in MD curl and slight decrease in CD curl by MD bending regardless of the winding methods(TSO, TSI). The water spray as back coating results in the remarkable reduction of CD curl regardless of the winding methods. Drying on flat dryer after spraying the moisture on back side display the most excellent effect on the reduction of CD curl.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.919-922
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• 2006

Comparing with the conventional transformer without the air gap, a contact-less transformer with the large air-gap (4.8cm) between the long primary winding and the secondary winding has the increased leakage inductance and the reduced magnetizing inductance. By the increased leakage inductance and the reduced magnetizing inductance on the primary of the contact-less transformer, a good deal of the primary current circulates through magnetizing inductance, which results in a massive loss in contact-less power supply (CPS). In this paper, the efficiency characteristics of the contact-less power supply using a series resonant converter is analyzed and simulated. The results are verified on the simulation based on the theoretical analysis and the 1.8kW experimental prototype.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.97-102
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• 2017

A current transformer (CT) is a type of sensor that consists of a combination of electric and magnetic circuits, and it measures large ac currents. When a large amount of current flows into the primary winding, the alternating magnetic flux in the iron core induces an electromotive force in the secondary winding. The characteristics of a CT are determined by the iron core design because the iron core is saturated above a certain magnetic flux density. In particular, when a large current, such as a current surge, is input into a CT, the iron core becomes saturated and the induced electromotive force in the secondary winding fluctuates severely. Under these conditions, the CT no longer functions as a sensor. In this study, the characteristics of the secondary winding were investigated using the time-difference finite element method when a current surge was provided as an input. The CT was modeled as a two-dimensional analysis object using constraints, and the saturation characteristics of the iron core were evaluated using the Newton-Rhapson method. The results of the calculation were compared with the experimental data. The results of this study will prove useful in the designs of the iron core and the windings of CTs.

• Journal of IKEEE
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• v.27 no.4
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• pp.587-600
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• 2023

This paper presents an optimal design of the slim type high frequency transformer used in the LLC DC to DC resonant converter for 65-inch UHD-TV with the rated power of 315W. This paper also performs an optimal design of the slim type high frequency through core loss analysis, AC winding loss analysis, and optimization design of the winding arrangement of the LLC resonant transformer. Particularly, the high-efficiency and slim type high frequency transformer based on the obtained results from theoretical analysis in this paper is constructed in the interleaved and vertical winding structures of its transformer to realize the winding method of automatic type and minimize AC winding loss. The primary and secondary windings of the slim type high frequency transformer the vertical winding structure proposed in this paper used the Litz-wire windings, PCB and copper plate windings, respectively. Finally, an optimal design of the slim type high frequency transformer proposed in this paper was carried out through the experimental results to confirm the validity of theoretical analysis based on the simulation results using Maxwell 2D and 3D tool.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.432-434
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• 2006

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) according to the number of the superconducting elements at the subtractive polarity winding of a transformer. The flux-lock type SFCL consists of the transformer with a primary winding and two secondary windings connected in parallel, and the superconducting element was connected with secondary winding in series, respectively. The applied voltage at that tin was 200V. when two superconducting elements of the secondary winding was connected in parallel, the peak lie current increased up to 99A, while that flowing in a superconducting element in conventional flux-lock type SFCL showed 50A under the same conditions, the impedance of secondary winding under the same situation showed the opposite behavior. This enabled the parallel structure to be easy to increase the capacity of power system, in the meantime, The quench between two superconducting elements in the SFCL with two secondary windings connected in parallel was achieved simultaneously. While the quench-starting point was slightly different in the SFCL with two superconducting elements connected in series. We found that the parallel connection between the secondary windings increased the power capacity and let quench characteristics improve through their mutual linkage.