• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1951-1953
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• 2005

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The piezoelectric transformers operated in each transformer's resonance vibration mode. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor $(k_p,\;k_{15})$ becomes effective rather than the transverse mode coupling factor ($k_{31}$). A single layer prototype transformer, 26[mm] in diameter and $1.5{\sim}4.0[mm]$ thick, was fabricated, such as step-up ratio, power transformation efficiency and temperature were measured.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.958-960
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• 2003

Although the researches and developments are performed for superconducting technologies, many problems such as AC loss and quench phenomenon still remain to design the superconducting transformer. In addition, pre-study on the three phase high temperature superconducting (HTS) transformer is a sort of time and expense consuming work, thus it is very worthy of being analyzing the characteristics of HTS transformer in advance through proper simulation programs and skills. This paper presents an effective simulation method for the three phase HTS transformer using components developed in the PSCAD/EMTDC.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.833-836
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• 1993

A flyback type power converter circuit for switched reluctance motor drives is presented. In this converter circuit, the energy extracted from an off going phase is stored in an additional capacitor. The energy stored is used to either be returned to the source frequently or energize the conducting phase during the conduction interval through the transformer. The additional switch to pass the energy stored in the capacitor to the source or the conducting phase is switched under a relatively low voltage condition. Its switching frequency is relatively high so that the size of the transformer can be reduced. The design guideline for the capacitor and the transformer is described. The effectiveness of the presented converter circuit is compared to other circuits through the analysis and experiment.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1920-1925
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• 2007

A transformer is a device that changes the current and voltage by electricity induced between coil and core steel, and it is composed of metals and insulating materials. In the core of the transformer, the thermal load is generated by electric loss and the high temperature can make the break of insulating. So we must cool down the temperature of transformer by external radiators. According to cooling fan's usage, there are two cooling types, OA(Oil Natural Air Natural) and FA(Oil Natural Air Forced). For this study, we used Fluent 6.2 and analyzed the cooling characteristic of radiator. we calculated 1-fin of detail modeling that is similar to honeycomb structure and multi-fin(18-fin) calculation for OA and FA types. For the sensitivity study, we have different positions(side, under) of cooling fans for forced convection of FA type. The calculation results were compared with the measurement data which obtained from 135.45/69kV ultra transformer flowrate and temperature test. The aim of the study is to assess the Fluent code prediction on the radiator calculation and to use the data for optimizing transformer radiator design.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.27-35
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• 2017

In this study, an integrated 2-in-1 transformer for a low-weight and low-cost light-emitting diode lighting power supply is proposed. In the transformer, a power factor correction (PFC) inductor and an LLC resonant transformer are placed and integrated on a single magnetic core. The amount of mutual interference, represented by the coupling coefficient, between magnetic fluxes generated from each magnetic source is minimized by using the new shape core of an integrated 2-in-1 transformer. The design consideration on critical conduction mode PFC converter and LLC resonant converter using the proposed 2-in-1 integrated transformer is described, and the overall performance of the 150 W LED PSU shown through the experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.472-482
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• 2007

The LLC series resonant converter with a LLT (Inductor-Inductor-Transformer) transformer design process and experimentation results for PDP TV power supply is presented. LLT transformer used to combine the inductor and transformer into one unit has the increased leakage inductance in the primary and secondary due to the winding method and the use of the gaped core. The increased leakage inductance in the primary and secondary of LLT transformer can be impacted on the DC voltage gain characteristics of LLC series resonant converter, In this paper, DC gain characteristics and the experimental results of the LLC series resonant converter with a LLT transformer are verified on the Math-CAD simulation based on the theoretical analysis and the 600W experimental prototype.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.48-57
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• 2021

The main research content of this paper is to evaluate the structural integrity and the cooling performance of 4250 kVA power transformer with ONAN(Oil Natural and Air Natural) mode. The dynamic analysis is used to verify the structural safety of the transformer by seismic loading. The transformer structure is simplified and NX software is used to build a three-dimensional model, and ANSYS commercial software is used to calculate the stress and deformation by applying corresponding load. The analysis result was evaluated whether it satisfies the design requirements according to the IEEE Std 693 standard. In terms of thermal analysis to evaluate the cooling performance, the thermal physical model is used to calculate the heat exchange between the radiator and the tank in the steady state, and the result is input into the Fluent software to calculate the internal temperature field of the transformer tank, which reduces the calculation cost of thermal fluid. Comparing the simulated hot spot temperature and top oil temperature of the transformer with the calculation results of the IEC60076 classic model, it is found that the error is only 1.9%.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.07a
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• pp.261-262
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• 2016

본 논문에서는 계기용변압기(Potential Transformer, PT) 1차권선의 절연내력을 향상시키기 위하여 전위분포가 일정하게 되도록 권선 배치를 최적화하는 프로그램을 작성하여 반복 분석하였다. 우선 기존의 권선 배치에 대한 국소점의 전계분포를 고찰하여 전계의 최대치를 구한 후, 권선 배치를 자동화된 순환 계산형 시뮬레이터를 제작하여 적절한 분포로 교정하고 최초의 기대 함수치를 극소화하는 형상을 반복 추적하는 알고리즘을 이용하였다.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.78-81
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• 2000

The backlight inverter used in a laptop computer is investigated in this paper. It has been difficult for the electromagnetic transformer in the inverter to have a high efficiency and compact profile. In this study the piezoelectric transformer(PT) is used to reduce the loss and volume compared to the standard electromagnetic transformer. Comparison with the experimental inverter with the PT has been shown to validated the simulation program using the equivalent circuit model of the PT. A simple dimming control circuit was experimentally demonstrated and shown to have broad control.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.357-360
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• 1995

Since the streaming electrification phenomena of transformer were made clear on 1970s, many researches have been continued on the improvement of the transformer. This paper describes the effect of additive (BTA, DBPC) and temperature on the streaming electrification of the various materials. The streaming current in the various materials decreases in proportion to the concentration of BTA, results in the inverse electrification. We believe that these results will contribute to the optimal design of HV large-capacity transformer.