• 전기의세계
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• v.13 no.2
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• pp.1-4
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• 1964

Phase transformation is used to change some phase from phase in A.C. system. We have been used Scott or Fork connection in phase transformation the otherwise phase transformation was constructed from M-G set. From this M-G set, we could make phase shift facilities by mannual. Now, I can derive more easy phase transformation from taking another method. I believe this new phase transformation method in the first thing in the world. And so, I am going to explain about phase transformer construction process. The first, we could devide into equal part of core around the iron core as to be same size. The second, you will make primary and secondary winding on the core. The third, when you will supplied three phase A.C. at the terminal of primary winding you can get e.m.f. inducing of some phase at secondary. And so, we could make phase change from some phase A.C. We can apply this principle in many fields, i.e., freequency changer, phase leader of no use condenser, voltage regulator in keeping balance, and D.C. generator. And more, I will introduce in details concerning main pinciple and theory through following chapter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.20-28
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• 1998

This study proposes a new method to estimate voltage unbalance more exactly using Thevenin's equivalent circuit. The conventional simple formula were easily applied to evaluate voltage unbalance. Because the formula was derived on the assumption that traction load would be directly connected to the secondary windings of the main transformer, they could not consider the detailed characteristics of traction power supply system, for example, self and mutual impedances of rail, catenary and return feeder. So, the ac쳐racy of the results could not be guaranteed. The proposed algorithm is applied to a standard autotransformer-fed test system to analyze unbalance phenomena. Through simulations, we could evaluate voltage and current unbalance factors and compare the voltage unbalance of the three transformer connection schemes : single phase, V- and Scott-connections which are required for suitable train operation schedules. Additionally, we could determine the combinations of trains which can be operated under the unbalance factor limits.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.8
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• pp.408-415
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• 2001

Using power semiconductor switches such as IGBTs, diodes and L-C circuits, novel repetitive impulse voltage generator is developed. In the presented circuits, high voltage pulse is generated by series-connection of capacitors and IGBTs. Therefore, the high voltage pulse is obtained by circuit configuration without any high voltage pulse transformer and high voltage dc source. Especially, the proposed circuit can operate up to several kHz and have high reliability and longer life than conventional ones. In also gives voltage balance of IBGTs automatically. So, the difference of characteristics of IGBTs and drive signal does not cause severe problems. To verify the proposed circuit, 20kV and 300A pulse generator is manufactured and tested.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.258-261
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• 2009

This paper proposes an earthing system without ground connection. As a Green IT Environmental Solution, Internal-external surge and other unnecessary electric currents are converted into energy and through a discharge the signal is reduced. It's a structure that discharges through a neutral electric transformer. The results show that the electric potential rising of the earthing system proposed in this paper are approximately below the half and the discharge currents increased approximately 9 times when compared to existent earthing systems. This earthing system is economical, easy to install and can solve environmental contamination.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.199-201
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• 2000

This paper describes the theory and experimental result of scaled model of STATCOM. The STATCOM, a solid-state voltage source inverter coupled with a transformer, is tied to a transmission line. A STATCOM inject an almost sinusoidal current of variables magnitude, at the pont of connection. This injected current is almost in quadrature with the line voltage, thereby emulating an inductive or capacitive reactance at the point of connection with the transmission line.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.439-440
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• 2015

한전의 전력계통망에 사용중인 345kV 변압기는 1차와 2차 권선의 일부회로를 공통으로 사용하는 단상 단권변압기를 사용하고 있다. 단상변압기로 인한 3차결선은 변압기 외부에서 알루미늄 부스바를 이용하여 모선을 구성한다. 한편, ${\Delta}$결선의 특징은 3차측 붓싱의 극성과 관련하여 결선방식에따라 3차측 위상이 1차측 위상보다 $30^{\circ}$진상 또는 지상의 위상특성을 가지고 있어 비율차동계전기 결선방식에 있어 주의를 요한다. 변압기는 YNautod1결선 또는 YNautod11으로 결선할 수 있다. 한편 비율차동기용 결선은 1차측과 2차측은 ${\Delta}$결선으로 3차측은 Y결선으로 비율차동계전기에 입력이 되어야 한다. 이때 3차측의 위상을 고려하여 1차측과 2차측의 CT ${\Delta}$결선은 변압기 결선방식과 동일한 결선으로 시행하여 한다.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1745-1747
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• 2002

This paper describes the effect of secondary surges entering low voltage side on the primary winding of pole transformers. After having connected the secondary winding by 4 different methods, surge voltages were applied to the low voltage side, and voltage waveforms were measured at a surge applied point and a high voltage bushing terminal. The measured voltages were compared by the waveform, magnitude and damping characteristics with each connection. As a result, the voltage waveforms induced by the secondary surges were different one another with each connection, especially, the conventional connecting method for 2 voltage sources was far different from the present method supplying only 1 voltage source in shape of the voltage waveform.

• 전기의세계
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• v.28 no.3
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• pp.51-56
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• 1979

The purpose of this paper is to study the conversion of single phase to three phase. In the proceeding of phase conversion, it is very convinence to convert two-phase from single phase using cycloconverter before and then two to three phase by scott connection transformer. There are also systematized zero-crossing, mono vibrator and ring counter circuit for the gate trigger circuits of cycloconverter. The wave forms of three phase by experimental results are analyzed and discussed the relation of phase difference among them.

• Journal of Power Electronics
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• v.8 no.2
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• pp.109-120
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• 2008

In this paper, a novel delta/double-fork transformer based 18-pulse full-wave AC-DC converter is designed, modeled, simulated and developed to feed isolated DC varying loads. The proposed AC-DC converter is used for low voltage and large current DC loads in applications such as electrowinning, where isolation is required mainly for stepping down the supply voltage. The proposed converter improves power quality at AC mains and meets IEEE-519 standard requirements at varying loads.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1678-1687
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• 2013

This paper describes a prototype of 3-phase 3.3kV/220V 6kVA modular semiconductor transformer developed in the lab for feasibility study. The developed prototype is composed of three single-phase units coupled in Y-connection. Each single-phase unit with a rating of 1.9kV/127V 2kVA consists of a high-voltage high-frequency resonant AC-DC converter, a low-voltage hybrid-switching DC-DC converter, and a low-voltage hybrid-switching DC-AC converter. Also each single-phase unit has two DSP controllers to control converter operation and to acquire monitoring data. Monitoring system was developed based on LabView by using CAN communication link between the DSP controller and PC. Through various experimental analyses it was verified that the prototype operates with proper performance under normal and sag condition. The system efficiency can be improved by adopting optimal design and replacing the IGBT switch with the SiC MOSFET switch. The developed prototype confirms a possibility to build a commercial high-voltage high-power semiconductor transformer by increasing the number of series-connected converter modules in high-voltage side and improving the performance of switching element.