• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.1-5
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• 2000

This paper deals with the modeling and analysis of the high voltage flyback transformer (HVFBT) often utilized in small-sized high voltage DC power supplies. The parasitic capacitance of th HVFBT with the large turns of the secondary winding causes the undesirable parasitic resonance in the transient state which produces the high current stress and limits the switching frequency of the converter. In order to analyze this phenomenon the equivalent circuit model including the parasitic capacitance is derived and the frequency characteristics are provided. The parasitic resonance in the switching states is also investigated based on this equivalent circuit model. The derived model and analysis is finally validated through the SPICE simulation and experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1166-1168
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• 2004

The high frequency series resonant converter has been widely used for the non-contact power supply system with the large air gap and the increased leakage inductance of the non-contact transformer. However. the high frequency series resonant converter has the disadvantages of high voltage gain characteristics in the overall load range due to the large air gap and the circulating magnetizing current. In this paper, unit voltage gain is revealed in the proposed three-level series-parallel resonant converter. The results are verified on the simulation results and the 5kW experimental prototype.

• 전력전자학회논문지
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• 제9권2호
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• pp.171-177
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• 2004

일반적으로 압전변압기는 고압을 출력하는 전원장치로 사용되고 있으나, 최근 어댑터와 같은 AC/DC 전원장치에 이를 채용하려는 움직임이 활발히 전개되고 있다. AC/DC 컨버터의 소형 경량화론 위해 기존의 권선형 변압기 대신 압전변압기는 AC/DC 컨버터용이 아닌 LCD 백-라이트구동용으로 제작된 압전변압기(piezoelectric transformer)를 사용하여 AC/DC 컨버터의 기본 특성을 고찰하고자 한다. 압전변압기의 재질, 특성 값으로부터 등가회로의 모델링을 수행하고, 이를 시뮬레이션과 실험을 통하여 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1383-1386
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• 2005

Non-isolated OSAKA Converter, which removes a three-phase transformer, is described in this paper. The converter switches once in every half cycle of an AC commercial power source. Therefore, it can solve many problems caused by the high frequency operation. The proposed converter achieves the soft-switching operation and the EMI noise can be reduced. In this circuit, the resonant capacitor, which is used for the soft-switching operation, is utilized for the improvement of an input current waveform. To achieve low cost and compact structure, non-isolated OSAKA converter removes a three-phase transformer of the OSAKA converter. By removing the three-phase transformer, three phase currents occur the interferences each other. To avoid the interference, a new switching method for non-isolated OSAKA converter is preposed. The converter can be constructed by the low-speed large power devices. The converter generates the low distorted input current waveforms with high power factor.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 학술대회 논문집
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• pp.377-382
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• 2005

This paper presents two new circuit topologies of DC bus lineside active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. One topology of proposed DC-DC converters is composed of a typical voltage source-fed full-bridge high frequency PWM inverter using DC busline side series power semiconductor switching devices with the aid of a parallel capacitive lossless snubber. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. It is proved that the more the switching frequency of full-bridge soft switching inverter increases, the more soft-switching PWM DC-DC converter with a hish frequency transformer link has remarkable advantages for its efficiency and power density as compared with the conventional hard-switching PWM inverter type DC-DC converter

• 조명전기설비학회논문지
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• 제22권4호
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• pp.166-171
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• 2008

본 논문은 가변주파수 스위칭 방식의 flyback 컨버터를 이용한 자동차용 35[W]급 고휘도 방전 램프용 전자식 안정기의 고효율 제어시스템을 구현하였다. 또한 안정기 성능, 크기 그리고 효율을 고려하여 planar 변압기를 이용하여 flyback 컨버터를 설계하였다. HID 램프를 자동차에 적용하기 위해 복잡한 과도특성을 제어할 수 있는 매우 복잡한 제어회로와 고효율의 안정기의 제작이 요구되어진다. 제안된 전자식 안정기는 planar 변압기를 사용한 flyback 컨버터, full bridge 인버터와 승압 점화장치로 구성되어 있으며, flyback 컨버터의 스위칭 주파수는 안정기에 입력전압의 변화에 따라 제어되도록 설계하였고, planar변압기를 사용하여, 안정기의 가격과 크기를 크게 절감할 수 있었다. 제안된 시스템에 대한 성능 및 효율은 여러 가지 실험을 통해 확인하였다.

• 한국철도학회논문집
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• 제19권4호
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• pp.436-444
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• 2016

철도차량용 주변압기 고압권선은 고압인통선에 유기되는 이상전압과 내부공진을 발생 시킬 수 있는 다양한 주파수 대역의 고유주파수를 가진다. 공장시험은 다양한 파형과 지속시간을 지닌 이상전압의 여자가능성을 판단하는데 한계가 있다. 본 연구는 전자계과도해석프로그램(이하 EMTP)을 이용하여 고압권선 모델을 설계하고 초기 전압분포와 전압-주파수 관계 측면에서 내부공진특성을 모의분석한다. 턴 단위의 집중매개변수는 변압기 형상정보부터 계산되며, 각 레이어 단위로 합산된 서브모델은 네트워크 모델로 결합되어 EMTP의 라이브러리를 통해 구현한다. 사례연구는 주파수 변동에 따른 레이어 단위의 전압-주파수 관계 특성과 시계열 영역에서 전압 확대 및 분포 양상을 보여준다.

• 전기학회논문지
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• 제62권12호
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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.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.781-789
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• 2018

This paper proposes a new approach utilizing empirical mode decomposition (EMD) reconstruction to process vibration signals of a transformer under DC bias caused by high voltage direction transmission (HVDC), which is the potential cause of additional vibration and noise from transformer. Firstly, the Calculation Method is presented and a 3D model of transformer is simulated to analyze transformer deformation characteristic and the result indicate the main vibration is produced along axial direction of three core limbs. Vibration test system has been built and test points on the core and shell of transformer have been measured. Then, the signal reconstruction method for transformer vibration based on EMD is proposed. Through the EMD decomposition, the corrupted noise can be selectively reconstructed by the certain frequency IMFs and better vibration signals of transformer have been obtained. After EMD reconstruction, the vibrations are compared between transformer in normal work and with DC bias. When DC bias occurs, odd harmonics, vibration of core and shell, behave as a nonlinear increase and the even harmonics keep unchanged with DC current. Experiment results are provided to collaborate our theoretical analysis and to illustrate the effectiveness of the proposed EMD method.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.291-294
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• 2007

Countries in the world are setting up policies to implement anti-global warning measures to actively cope with the Agreement on Climate Change. Rising problems related to energy and environment prompted research and development efforts to highly efficient electric instrument and environmentally friendly products to secure resources and save energy Korea's high dependency on imported energy and its lack in natural resources make it urgently necessary to develop energy efficient instrument and equipment that can save energy. Every household now uses a transformer, which is very important instrument among others. A variety of technologies to manufacture transformers are currently used along with efforts to develop new materials. Development nit of high efficient transformers is called for by the time and has direct economic impact on suppliers and consumers. In addition, it is desirable to install a transformer that is trustworthy, secure, low on loss, anti-incident capable, small, anti-flammable, environmentally friendly, cost-efficient high-frequency resistant and easy for maintenance. To do this, it is necessary to look deeper into a highly efficient transformer that can save energy. This paper will discuss the types and characteristics of various transformers and propose ways to save energy and raise efficiency tv analyzing a environmentally friendly amorphous transformer.