• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(5)
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• pp.9-12
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• 2000

This paper describes the modeling and experimental results of coreless printed circuit board (PCB) based transformer that can be used for power conversion at high frequency operation. The principle of using coreless PCB based transformer in 2MHz, 10W class ZVS Flyback DC-DC converter has been successfully demonstrated. The maximum power conversion efficiency is 79%. Even for high operating frequency, an efficiency greater than 70% can be obtained with under 1% regulation error.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.885-886
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• 2006

We have proposed a 100 MVA, 3 phases, 154 kV class HTS transformer which will substitute for 60 MVA conventional transformer. In this paper, we designed conceptually the structure of the superconducting windings of a single phase 33 MVA transformer. The power transformer of 154 kV class has a tertiary winding besides primary and secondary windings. So the HTS transformer should have the 3rd superconducting winding, it makes the cost of the HTS transformer high and the efficiency low. Further more we considered On Load Tap Changer (OLTC) in HTS power transformer. OLTC equipment is required for fitting to a power transformer by which the voltage ratio between the windings can be varied while the transformer is on load. We analyzed the electrical characteristics of the HTS transformer such as magnetic stress and AC loss.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.683-686
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• 2001

This paper presents a novel prototype of the utility­interactive voltage source type sinewave pulse modulated power inverter using a high-frequency flyback transformer link. The proposed power conditioner circuit for the solar photovoltaic generation and small scale fuel cell has an isolation function due to the safety of the power processing system, which is more cost effective and acceptable for the small-scale distributed renewal energy conditioning and processing systems. The discontinuous current mode(DCM) of this power processing conversion circuit is applied to implement a simple circuit topology and pulse modulated control scheme. Its operation principle is described on the basis of simulation evaluations and theoretical considerations. The simulation results obtained herein prove that the proposed inverter outputs with sinusoidal waveforms and unity power factor currents are synchronized to the main voltage in utility power source grid. In this paper, the soft switching topology of high­frequency linked sinewave pulse modulation inverter is proposed and discussed.

• Transactions on Electrical and Electronic Materials
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• 제15권3호
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• pp.113-116
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• 2014

Power transformer insulation oil is critical to the useful life of the transformer. Although mineral base insulation oil is the most common type of transformer insulation oil in use, environmental and safety concerns has encouraged the development of biodegradable alternatives. Today, $Envirotemp^{(R)}\;FR3^{TM}$ is in commercial use and this study is aimed at ascertaining the possibility of applying the oil in Malaysia power transformers. A sample of $Envirotemp^{(R)}\;FR3^{TM}$ was tested to measure and compare the technical (including electrical, chemical and physical) properties of the oil according to Malaysian standards. The study found that the oil sample had better qualities, such as higher dielectric strength, lower dissipation factor, higher flash and fire points, higher moisture absorption capability, and less dissolved gases composition amongst others. However, it was also ascertained that further development in this area could be hindered due to Malaysia's lack of standards for biodegradable oil.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2152-2154
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• 1999

In this paper, we suggested the design rule of high-voltage rectangular waveform generator working in low frequency domain (5Hz $\sim$ 60Hz). Most of the commonly used power electronic switching devices have voltage ratings up to several kV. So it is difficult to design and fabricate high-voltage switching systems with the power electronic devices alone. We have combined IGBTC(1200V, 50A) with the specially designed transformer to get the high-voltage rectangular waveforms up to 40kV. In this work. next two things are the main factors. The first one is design of transformer working low-frequency domain close to 5Hz. And the second one is additional voltage source to floating the transformer voltage output. As a result, we can get frequency-variable and high-voltage rectangular voltage waveform and this can be a more efficient power source of sandpaper manufacturing process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.177-181
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• 1997

A new piezoelectreic transformer is proposed as a key device for high power transimssion. The piezoelectric transformer made of lead titanate solid solution creamic is operated with a thickness extensional vibration mode. This transformer can operate at high frequency aver several megahertz with about 90% high efficiency.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.114-120
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• 2014

In this paper, a method for multi-physics analysis of the temperature-dependent properties of an oil-immersed transformer is discussed. To couple thermal fields with electromagnetic and fluid fields, an algorithm employing a user defined function (UDF) is proposed. Using electromagnetic analysis, electric power loss dependent on temperature rise is calculated; these are used as input data for multi-physics analysis in order to predict the temperature rise. A heat transfer coefficient is applied only at the outermost boundary between transformer and the atmosphere in order to reduce the analysis region. To verify the validity of the proposed method, the predicted temperature rises in high-voltage (HV) and low-voltage (LV) windings and radiators were compared with the experimental values.

• Progress in Superconductivity
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• 제7권2호
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• pp.162-166
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• 2006

We have proposed a 3 phase, 100 MVA, 154 kV class HTS transformer substituting for a 60 MVA conventional transformer. The power transformer of 154 kV class has a tertiary winding besides primary and secondary windings. So the HTS transformer should have the 3rd superconducting winding. In this paper, we designed conceptually the structure of the superconducting windings of a single phase 33 MVA transformer. The electrical characteristics of the HTS transformer such as % impedance and AC loss vary with the arrangement of the windings and gaps between windings. We analyzed the effects of the winding parameters, evaluated the cost of each design, and proposed a suitable HTS transformer model for future power distribution system.

• 전력전자학회논문지
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• 제18권2호
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• pp.169-177
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• 2013

This paper proposes a new configuration of bidirectional intelligent semiconductor transformer with rating of 1.9kV/127V, 2kVA. The proposed transformer consists of high-voltage high-frequency AC-DC rectifier, and low-voltage DC-DC and DC-AC converters. The operational feasibility of proposed transformer was verified by computer simulation with PSCAD/EMTDC software. Based on the simulation results, a hardware prototype with rating of 1.9kV/127V, 2kVA was built and tested in the lab to confirm the feasibility of hardware implementation. Using three units of this transformer, a 3-phase transformer with rating of 3.3kV/220V, 6kVA can be built.

• 전력전자학회논문지
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• 제9권6호
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• pp.560-567
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• 2004

이 논문에서는 Planar transformer를 적용한 30W급 포워드 컨버터에 대한 설계와 실험결과를 소개한다. 컨버터의 전체적인 크기와 체적은 일반적인 권선형 변압기 대신 Planar transformer를 적용함으로써 감소하였고 크기와 체적의 감소로 포워드 컨버터의 전력밀도가 증가하였다. 또한, Single Switch 포워드 컨버터 와 Active Clamp ZVS 포워드 컨버터를 비교연구 하였다.