• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.538-544
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• 2010

This paper proposes an estimation algorithm for the separate primary and secondary leakage inductances of a three phase $Y-\Delta$ transformer using least squares method. The voltage equations from the primary and secondary windings are combined into a differential equation to estimate the separate primary and secondary leakage inductances in order to use the line current of the delta winding. Separate primary and secondary leakage inductances are obtained by applying least squares method to the differential equation. The performance of the proposed algorithm is validated under transient states, such as magnetic inrush and overexcitation, as well as in the steady state with various cut-off frequencies of low-pass filter. The proposed technique can accurately generate separate leakage inductances both in the steady and transient states.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.156-159
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• 2002

This paper presents an experimental study of the surge response characteristics for the primary winding of a pole transformer and ultimately aims at devising countermeasures against the surge in operating transformer. After applying the impulse voltage to the primary of the 30 kVA pole transformer with single bushing, the voltage waveforms were measured at each tap lead and compared with one another. As a result, the voltage peak of the surge propagating in the primary was decreased in magnitude at a constant rate and somewhat delayed compared to the peak of the applied surge as the tap leads were getting closer to the grounding terminal. The voltage measured at the secondary was not delayed in time, different from that at the primary, and it was about 1/6 according to the turn ratio.

• Journal of Power Electronics
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• v.13 no.2
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• pp.214-222
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• 2013

This paper proposes a high efficiency step-down flyback converter using a coaxial-cable coupled-inductor which has a higher primary-secondary flux linkage than sandwich winding transformers. The structure of the two-winding coaxial cable transformer is described, and the coupling coefficient of the coaxial cable transformer and that of a sandwich winding transformer are compared. A circuit model of the proposed transformer is also obtained from the frequency-response curves of the secondary short-circuit and of the secondary open-circuit. Finally, the performance of the proposed transformer is validated by the experimental results from a 35W single-output flyback converter prototype. In addition, the proposed two-winding coaxial transformer is extended to a multiple winding coaxial application. For the performance evaluation of the extended version, 35W multi-output hardware prototype of the DC-DC flyback converter was tested.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.18-20
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• 2007

A coupling capacitor voltage transformer (CCVT) is used in an extra high voltage power system to obtain the standard low voltage signal for protection and measurement. To suppress the effects of ferro-resonance more effectively, a three winding CCVT is used. This paper proposes an algorithm for compensating the secondary voltage of the three winding CCVT. With the secondary voltage of the three winding CCVT, the secondary and tertiary currents are obtained; the primary winding current is obtained by considering non-linear characteristics of the core; the voltage across the capacitor and the inductor are calculated and then added to the measured voltage to compensate the secondary voltage. Test results indicate that the algorithm can reduce the errors of the three winding CCVT significantly.

• Journal of Power Electronics
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• v.19 no.1
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• pp.296-306
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• 2019

The flyback topology is being widely used in power adapters. The coupling capacitance between primary and secondary windings of a flyback transformer is the main path for common-mode (CM) noise conduction. A Y-cap is usually used to effectively suppress EMI noise. However, this results in problems in space, cost, and the danger of safety leakage current. In this paper, the CM noise behaviors due to the electric field coupling of the transformer windings in a flyback adapter with synchronous rectification are analyzed. Then a scheme with balance winding is proposed to reduce the CM noise with a transformer winding design that eliminates the Y-cap. The planar transformer has advantages in terms of its low profile, good heat dissipation and good stray parameter consistency. Based on the proposed scheme, with the help of a full-wave simulation tool, the key parameter influences of the transformer PCB winding design on CM noise are further analyzed. Finally, a PCB transformer for an 18W adapter is designed and tested to verify the effectiveness of the balance winding scheme.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.458-460
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• 2001

This paper described the unbalanced voltage on the tertiary bus of a single Phase auto transformer in the case of parallel operation with different manufacturer at each Phase. The unbalanced capacitances between primary to secondary winding, secondary to tertiary winding and primary to tertiary winding makes unbalanced bus voltage in the tertiary bus side. The unbalanced voltage let the surge arrester to operate in the power frequency range, and it causes the arrester to burn out. The failure of the arrester at one phase makes line to ground fault, which lead to the surge arrester failure of the other two phase on the tertiary bus.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.130-132
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• 1997

In this paper, we propose a new type of tubular linear induction motor(TLIM) with two-dimensional motion. The proposed motor consists of four short primary LIMs arranged on a same circumference and a common secondary. By adopting independently energized ring-windings to the primary, we can expect the reduction of coil-end region and the freedom of alternating current supply. The secondary conductor is capable of producing anyone of rotary, linear, and helical motions by controlling the phase of supply currents in each primary winding. From the 3-D finite element analysis and the experiment, we derive the feeding conditions to increase the subsidiary rotary-force and an optimal arrangement of primary currents to reduce the number of slot.

• Journal of IKEEE
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• v.26 no.3
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• pp.445-455
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• 2022

This paper presents the optimal design of flyback transformer with the flat copper winding method of injection type suitable for the small-size and winding method of automatic type used in 90W DC to DC converter for LED-TV. This paper also proposes the flyback transformer with the flat copper winding method of injection type capable of the winding method of automatic type and the reduction of transformer size and enhanced uniformity in electrical characteristics compared to the conventional mass-production flyback transformer with the winding method of manual type. In particular, the flat copper winding transformer of injection type proposed in this paper is constructed in a vertical winding method of its transformer to realize the winding method of automatic type. The primary and secondary windings of flyback transformer with the flat copper winding method of injection type used the conventional winding, triple insulated winding and the flat copper winding method of injection type, respectively. The optimal design of flyback transformer with the flat copper winding transformer of injection type proposed in this paper suitable for small-size and winding method of automatic type was carried out based on the simulation results using Maxwell 2D and 3D tool.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1274-1279
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• 2011

The purpose of this paper is to present the manufacturing defect and damage pattern of a 3 phase 22.9/3.3kV oil immersed transformer, as well as to present an objective basis for the prevention of a similar accident and to secure data for the settlement of PL related disputes. It was found that in order to prevent the occurrence of accidents to transformers, insulating oil analysis, thermal image measurement, and corona discharge diagnosis, etc., were performed by establishing relevant regulation. The result of analysis performed on the external appearance of a transformer to which an accident occurred, the internal insulation resistance and protection system, etc., showed that most of the analysis items were judged to be acceptable. However, it was found that the insulation characteristics between the primary winding and the enclosure, those between the ground and the secondary winding, and those between the primary and secondary windings were inappropriate due to an insulating oil leak caused by damage to the pressure relief valve. From the analysis of the acidity values measured over the past 5 years, it is thought that an increase in carbon dioxide (CO2) caused an increase in the temperature inside the transformer and the increase in the ethylene gas increased the possibility of ignition. Even though 17 years have passed since the transformer was installed, it was found that the system's design, manufacture, maintenance and management have been performed well and the insulating paper was in good condition, and that there was no trace of public access or vandalism. However, in the case of transformers to which accidents have occurred, a melted area between the upper and the intermediate bobbins of the W-phase secondary winding as well as between its intermediate and lower bobbins. It can be seen that a V-pattern was formed at the carbonized area of the transformer and that the depth of the carbonization is deeper at the upper side than the lower side. In addition, it was found that physical bending and deformation occurred inside the secondary winding due to non-uniform pressure while performing transformer winding work. Therefore, since it is obvious that the accident occurred due to a manufacturing defect (winding work defect), it is thought that the manufacturer of the transformer is responsible for the accident and that it is lawful for the manufacture to investigate and prove the concrete cause of the accident according to the Product Liability Law (PLL).

• Transactions on Electrical and Electronic Materials
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• v.18 no.1
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• pp.42-45
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• 2017

In this paper, a transformer type SFCL (superconducting fault current limiter) using an additional magnetically coupled circuit was suggested. Its transient fault current limiting characteristics, due to the winding direction of additional coupled circuit, were analyzed through fault current limiting tests. The suggested transformer type SFCL was composed of the primary winding, and one secondary winding wound on the same iron core together with an additional magnetically coupled circuit. That circuit consists of the other secondary winding together with the other SC (superconducting) element connected in parallel with its other secondary winding. As one of the effective design parameters to affect the transient fault current of the SFCL, the fault current limiting tests of the suggested SFCL were carried out considering the winding direction of its additional coupled circuit. It was confirmed that, through the analysis on the fault current tests of the SFCL, the quench sequence of two SC elements comprising the suggested SFCL could be adjusted by the winding direction of the additional coupled circuit.