• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.581-585
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• 2001

This paper describes novel high voltage capacitor(HVC) embedded high frequency transformer and novel inverter power supply topology for driving magnetron in microwave oven. This transformer is used to achieve down­sizing, low-cost and efficiency improvement. Proposed transformer has HVC in its secondary winding. Therefore, this transformer does not need external high voltage capacitor which used in conventional power supply. As use of this transformer, output voltage is shifted from ground to above 2000[V] and efficiency of microwave oven can be improved. The weight of proposed transformer is about one sixth of conventional one and efficiency is improved by seven percent compared to the efficiency of the conventional system.

• Journal of Magnetics
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• v.19 no.3
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• pp.295-299
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• 2014

Recently, module-integrated converter (MIC) research has shown interest in small-scale photovoltaic (PV) generation. The converter is capable of efficient power generation. In this system, the high frequency transformer should be made compact, and demonstrate high efficiency characteristics. This paper presents a core structure optimization procedure to improve the efficiency of a high frequency transformer of compact size. The converter circuit is considered in the finite element analysis (FEA) model, in order to obtain an accurate FEA result. The results are verified by the testing of prototypes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.1
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• pp.96-101
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• 2016

In this paper, We investigate the number of 795 transformer in the private electrical facilities and analyze the annual load factor. The results show that the annual load factor of transformer is 20.16% in manufacturing industry, education services(school) is 9.59%, retail and wholesale services is 19.68%, resort and leisure industry is 10.93%, office building is 13.10%, and apartment houses is 14.69%. Education services, resort and leisure industry are being operated with a very low annual load factor. The relatively small capacity of less than 500kVA transformer also been analyzed that is being operated with a low load factor. Therefore, In order to minimize the power loss of the transformer, it is advisable to complement the Transformer Efficiency Management system to be designed the efficiency is good transformer when the load is low. Analysis results will be used as the basis for the provision of transformer efficiency management system and be used High-efficiency transformers promotion system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.180-187
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• 2004

A conventional power supply of a microwave oven has a 60Hz transformer and high voltage capacitor(HVC). Though it is very simple and has low cost, it has several problems such as large size, heavy weight and low efficiency To improve these problems, various high frequency inverter type power supply have been investigated and developed in recent years. But these cost is higher than the conventional one due to additional control circuit, fast switching devces. In this paper, a novel pulse power supply for microwave oven using high frequency transformer embedded HVC(High Voltage Capacitor) is proposed for down-sizing, cost reduction and efficient improvement. To verify the effectiveness of the proposed transformer, an equivalent circuit of transformer embedded HVC is derived and it's characteristic is described. And the validity of the proposed pulse power supply embedded HVC-high frequency transformer is shown by simulations and experiments accroding to various operating conditions.

• 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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.4
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• pp.29-35
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• 2014

The purpose of high frequency transformer in the inverter is to reduce the voltage and current stresses of switch components when it operates at the large conversion ratio. But the loss of transformer is the major contributor in the efficiency of inverter. This paper presents the method of core design to minimize the loss of transformer. The total loss of transformer is minimized by adjusting the effective cross-sectional areas of core. The component ratio of losses are compared by using the finite-element analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.1005-1009
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• 2008

The high efficiency insulation panel for transformer construction is needed in residential area because the making noise from transformer substation in side of city is appeared a lost of problem by increasing to conserve the living environment. Therefor in this paper, first the vibration and noise characteristic of existing insulation panel is analyzed according to attached material, cork and sponge-type. Second the insulation of sound performance is compared between the existing insulation panel. And high efficiency insulation panel that is proposal in this paper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.502-507
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• 2004

The forward planar transformer, which had power capacity of 300 W, input voltage of 220 V, output voltage of 15 V, and switching frequency of 300 KHz, was designed and manufactured by using the planar core with large effective area and the flat copper leadframes for miniaturization and high efficiency of the switching mode power supply (SMPS). As well as, a forward converter equipped with the above mentioned planar transformer was manufactured and electromagnetic characteristics were investigated. The numerical value of turns for 1st and 2nd winding were 15 and 2 respectively The self inductance of 1st winding was 1.592 mH, very low leakage inductance of 2.7 $\mu$H, and the coupling factor of 0.928 were obtained at switching frequency of 300 KHz. The high efficiency of 88.62 % for the SMPS equipped with planar transformer was obtained at power capacity of 300 W.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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• pp.539-545
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• 2012

Due to merits cost and efficiency, the transformer-less type photovoltaic (PV) inverters have been popularized in the solar market. However, the leakage current flowing through a parasitic capacitor between PV array and ground can cause adverse effect in the transformer-less PV system. In this paper, a bi-directional PV inverter with high efficiency and low noise is proposed for the PV system with an energy storage device. The proposed inverter is a transformer-less type and performs the bi-directional power control between dc sources and grid with high efficiency. In addition, the proposed inverter can suppress the leakage current and obtain low noise characteristic. Finally, 3-kW prototype was implemented to confirm validity of the proposed inverter.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1468-1479
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• 2015

Renewable energy resources such as wind and photovoltaic power generation systems demand a high step-up DC-DC converters to convert the low voltage to commercial grid voltage. However, the high step-up converter using a transformer has limitations of high voltage stresses of switches and diodes when the transformer winding ratio increases. Accordingly, conventional studies have been applied to series-connect multioutput converters such as forward-flyback and switched-capacitor flyback to reduce the transformer winding ratio. This paper proposes new single-ended converter topologies of an isolation type and a non-isolation type to improve power efficiency, cost-effectiveness, and output ripple. The first proposal is an isolation-type charge-pump switched-capacitor flyback converter that includes an extreme-ratio isolation switched-capacitor cell with a chargepump circuit. It reduces the transformer winding number and the output ripple, and further improves power efficiency without any cost increase. The next proposal is a non-isolation charge-pump switched-capacitor-flyback tapped-inductor boost converter, which adds a charge-pump-connected flyback circuit to the conventional switched-capacitor boost converter to improve the power efficiency and to reduce the efficiency degradation from the input variation. In this paper, the operation principle of the proposed scheme is presented with the experimental results of the 100 W DC-DC converter for verification.