• Journal of IKEEE
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• v.18 no.1
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• pp.31-36
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• 2014

In this paper, self-resonant characteristics of transformers were analyzed in accordance with changes of characteristics regarding to the stray capacitance, the volume of winding and the winding ratio were organized by formulas. Generally, the stray capacitance is considered as an unnecessary factor in processing transformers design as well as one of the inherent characteristics. In particular, these characteristics can be appeared clearly in the high frequency driving and Electrical resonance occurs in transformer, according to coupling with a magnetic factor at a particular frequency. In the case of high-voltage output applications, such as medical equipments, It is required to output high-voltage gain. Therefor, If Self-Resonant Characteristic is applied to High-Voltage transformer design, Not only the transformer and circuit but also related the system size can be reduced. So we propose it as one of additional high voltage transformer design methods.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.16-21
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• 2005

In paper, propose new partial resonance ZCS PWM controlled High frequency insulating Full-bridge DC/DC converter not using exciting current of high frequency transformer. It is compared with the existing principles in characteristics. It also realizes a widely stabilized ZVS operating using new ON-OFF control method at synchronized power rectification MOSFET of high frequency insulating transformer secondary. Besides, it is brought over 97[%] measurement efficiency by proposed DC-DC converts. It is proved effectiveness of new methods using DC UPS PWM rectifier as switching power supply.

• Journal of Power Electronics
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• v.4 no.4
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• pp.237-245
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• 2004

In this paper, a two-switch high frequency flyback transformer linked zero voltage soft switching PWM DC-DC power converter implemented for distributed DC- feeding power conditioning supplies is proposed and discussed. This switch mode power converter circuit is mainly based on two main active power semiconductor switches and a main flyback high frequency transformer linked DC-DC converter in which, two passive lossless quasi-resonant snubbers with pulse current regeneration loops for energy recovery to the DC supply voltages composed of a three winding auxiliary high frequency pulse transformer, auxiliary capacitors and auxiliary diodes for inductive energy recovery discharge blocking due to snubber capacitors are introduced to achieve zero voltage soft switching from light to full load conditions. It is clarified that the passive resonant snubber-assisted soft switching PWM DC-DC power converter has some advantages such as simple circuit configuration, low cost, simple control scheme, high efficiency and lowered noises due to the soft switching commutation. Its operating principle is also described using each mode equivalent circuit. To determine the optimum resonant snubber circuit parameters, some practical design considerations are discussed and evaluated in this paper. Moreover, through experimentation the practical effectiveness of the proposed soft switching PWM DC-DC power converter using IGBTs is evaluated and compared with a hard switching PWM DC-DC power converter.

• Journal of Electrical Engineering and Technology
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• v.1 no.4
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• pp.534-542
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• 2006

This paper presents results of frequency domain spectroscopy (FDS) measurements on oil-impregnated pressboard insulation, their analyses and use of the data for modeling high frequency response (FRA) of transformers. The dielectric responses were measured in a broad frequency range, i.e. from 0.1 mHz to 1 MHz, on model samples containing different amount of moisture. The responses were parameterized with terms representing dc conductivity, low frequency dispersion and Cole-Cole polarization mechanisms and they were thereafter used to model the FRA response of a three-phase transformer.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.1
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• pp.33-39
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• 2005

Comparing with the conventional transformer without the air gap, a contactless transformer with the large air gap between the long primary winding and the secondary winding has increased leakage inductance and reduced magnetizing inductance. For transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the contactless power supply system with the large air gap and the increased leakage inductance of the contactless transformer However, the high frequency series resonant converter has the disadvantages of the low efficiency and high voltage gain characteristics in the overall load range due to the large air gap and the circulating magnetizing current. In this paper, the characteristics of the high efficiency and unit voltage gain are revealed in the proposed three-level series-parallel resonant converter. The results are verified on the simulation based on the theoretical analysis and the 5kW experimental prototype.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.584-588
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• 2001

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage Capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, A new pulse power supply for Microwave Oven using novel HVC embedded high frequency transformer is proposed for down-sizing, cost reduction, and efficiency emprovement of Inverter type power supply. Also, equivalent circuit model is derived by impedance measurements. And the operation of proposed pulse power supply is verified by simulations and experimental results.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.338-342
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• 2006

This paper analyzed the power loss of transformers considering the magnetic component. For this, each winding strategy and the effect of air gap between the ferrite core have been an important variable for optimal parameter calculation. Inductors are very well known design rules to devise, but the performance of the flyback converter as a function of transformer winding strategy has not been fully developed. The transformer analysis tool used was PExpert. The influence of the insulator thickness, effect of the air gap, how the window height and variation of the capacitive value effects the coil and insulator materials are some of parameters that have been analyzed in this work. The parameter analysis is calculated to a high frequency of 48[kHz]. Therefore, the final goal of this paper was to calculate and adjust the parameters according to the method of winding array and air gap minimizing the power loss.

• Journal of Power Electronics
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• v.9 no.2
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• pp.180-187
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• 2009

When converters operate in megahertz range, the passive components and magnetic devices generate high losses. However, the eddy current issues and choices of magnetic cores significantly affect on the design stage. Apart from that, the components' reduction, miniaturization technique and frequency scaling are required as well as improvement in thermal capability, integration technique, circuit topologies and PCB layout optimization. In transformer design, the winding and core losses give great attention to the design stage. From simulation work, it is found that E-25066 material manufactured by AVX could be the most suitable core for high frequency transformer design. By employing planar geometry topology, the material can generate significant power loss savings of more than 67% compared to other materials studied in this work. Furthermore, young researchers can use this information to develop new approaches based on concepts, issues and methodology in the design of magnetic components for high frequency applications.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2027-2029
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• 1998

We have developed a compact high frequency switch mode converter (HFSMC) power supply with DC 50 kV output voltage and 10 kW output power. Since the inverter circuit uses 25 kHz rescharging scheme, the current is flowing with t kHz. For the efficient output voltage transform performed a simple design process using the transformer principle and the commercial specification. For the DC 50 kV output, we employed 7 pa windings of secondary coils for the series stac connection of the output with full-bridge rectifi In this paper the design detail and the test re the high frequency transformer together with HFSMC power supply are presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.2000-2004
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• 2009

In general, for the condition monitoring of a power transformer using the UHF PD measuring technique, detection of any partial discharge, identifying the defect in the transformer and locating the insulation defect are necessary. In this paper one of the most frequent detects which can result in turn to turn fault in power transformer was examined for identifying the defect. In order to model the defect, as a discharge source, a partial discharge cell was used for experimental activity. Magnitude of electromagnetic wave signals and corresponding amount of apparent discharge were measured simultaneously against phase of applied voltage to the discharge cell. Frequency range and phase resolved partial discharge signals were measured and analyzed. The results will be contributed to build the defect database of power transformer and to decrease the occurrence of transformer faults.