• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.11B no.4
• /
• pp.180-184
• /
• 2001

The high operation frequency mainly reduces transformer volume in the power supply. A high frequency and high voltage pulse transformer is designed, fabricated, and tested. Switching frequency of the transformer is 100 kHz. Input and output voltages of the transformer are 250 V and 4 kV, respectively. Normal operation power of the transformer is 3 kW. Maximum volume of the transformer is 400 $cm^3$. The power density is thus 7.5 W/$cm^3$. The transformer will be installed in a metal box that has nominal operation temperature of 85 degree centigrade. The transformer and other high voltage components in the box will be molded with Silicon RTV(Room Temperature Vulcaniza) that has a very low thermal conductivity. Procedure of design and test results are discussed. Analytical as well as experimental results of varous paramters such as transformer loss, leakage inductance, distributed capacitance are also discussed. In addition, thermal analysis results from ANSYS code for three different operation conditions are discussed.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1892-1897
• /
• 2010

In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. PSIM(Power Electronics Simulator) is optimal simulation software in field of the power electronics and provide the simple and convenient user interface. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using PSIM.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.2317-2322
• /
• 2011

In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using Sinulink.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.8
• /
• pp.30-35
• /
• 2013

This paper describes the assessment method of deterioration condition for a power transformer using SFRA. Frequency Response Analysis(FRA) is a method to evaluate the mechanical and geometrical integrity of the core and windings within a power transformer by measuring the electrical transfer functions over a wide frequency range. SFRA is sweep frequency response analyzer for power transformer winding diagnosis. The FRA is a comparative method, that evaluates the transformer condition by comparing the obtained set of FRA results to reference results on the same, or a similar, unit. FRA techniques were widely used and much more sensitive than the traditional and internationally accepted method of impedance measurements, but that work was required on standardization and interpretation. In order to analyze the deterioration condition for power transformer, overvoltage test and mechanical distortion test were carried out. The deterioration condition for power transformer was evaluated by SFRA. It is intended to present the elemental technology of assessment method for power transformer using SFRA.

• Journal of the Korean Society of Safety
• /
• v.15 no.1
• /
• pp.106-111
• /
• 2000

EP(Electrostatic Precipitator) has been used to keep the natural environment from fly-ash in the industrial fields and operated in intermittent PEC(Pulse Energized Control) mode to improve dust-collecting efficiency. Intermittent PEC mode induces low-frequency harmonic currents into power system, therefore EP transformer vibrates. This continuous transformer vibration developes transformer abnormal audio-noise and if it is too much or operates in the region of natural frequency, transformer will be damaged in the end. EP interruption caused by transformer damage results in power generation stopped, power quality down and economic loss. Therefore, this paper explains harmonic currents and transformer vibration-core vibration, winding vibration, and proposes the measures of suppressing the vibration with EP operated in intermittent PEC mode. And this results is proposed to be used for future EP transformer design or EP control method to operate EP-concerned equipment safely keeping from system faults caused by transformer vibration.

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

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.5
• /
• pp.206-212
• /
• 2005

In this paper, criterion and algorithm for on-line dissolved gas of a Power transformer are studied. For the initial diagnosis of a power transformer, the on-line dissolved gas analysis is one of the most important and acceptable item to preventively diagnose a power transformer. But the criterion and algorithm of this item are not established yet in korea. In this paper, criterion and alarm level of the on-line dissolved gas analysis are based on the analysis of on-line data of operating transformers, Korea industrial standard and operation manual for a power transformer as well as accumulated data of the preventive diagnosis systems which have been operated at nine substations of Korea Electric Power Co.(KEPCO) since 1997, Therefore, the criterion and alarm level proposed in this paper are to be well suitable and are adaptable for the domestic operational environments and conditions of the power transformer. Considering that the conventional diagnosis system is capable only of accumulating and monitoring data of the power transformer operation, the criteria and the algorithms make it possible to accomplish an ultimate goal of the preventive diagnosis system. It is expected, therefore, that they will have a beneficial effect on broad applications of the preventive diagnosis system and the achievement of manless substation system in the future.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.2
• /
• pp.119-126
• /
• 2010

An integrated magnetic (IM) transformer is proposed for a phase shifted full bridge (PSFB) converter with zero voltage switching (ZVS). In a proposed IM transformer, the transformer is located on the center leg of E-core and the output inductor is wound on two outer legs with air gap. The proposed IM transformer is analyzed by using the magnetic capacitor model. For reducing the core size, EE core is redesigned. The proposed IM transformer is experimentally verified on a 1.2 kW prototype converter. The converter efficiency with the proposed IM transformer is about 93 % at full load and its volume size can be reduced. It can be expected that the power density can be largely increased with the proposed IM transformer.

• Journal of Power Electronics
• /
• v.8 no.3
• /
• pp.217-227
• /
• 2008

The electric power subsystems (EPS) of most remote sensing satellites consist of a solar array as a source of energy, a storage battery, a power management and control (PMC) unit and a charge equalization unit (CEU) for the storage battery. The PMC and CEU use high frequency transformers in their power modules. This paper presents a design, implementation and testing results of a high frequency transformer for the EPS of satellite applications. Two approaches are used in the design process of the transformer based on the pre-determined transformer specifications. The transformer is designed based on an ETD 29 ferrite core. The implemented transformer consists of one center-tapped primary coil with eleven center-tapped secondary coils. The offline calculation results and measured values of R, L for transformer coils are convergence. A test circuit for measuring the transformer parameters like voltage, current and B-H hysteresis was implemented and applied. The test results confirm that the voltage waveforms of both primary and secondary coils were as desired. No overlapping occurred between the control signal and the transformer, which was not saturated during testing even during a short circuit test of the secondary channels. The dynamic B-H loop characteristics of the used transformer cores were measured. The sample test results are given in this paper.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.1425-1430
• /
• 2004

In this paper, the inductive power transformer using electromagnetic induction for the road/railway applied to contactless power transfer system is suggested and some ideas for power collector design to improve the power transfer performance are presented. The proposed the inductive power transformer is used for the light railway/road transportation system. which has a large air-gap and demands a large electrical power capability. But. low output power is generated due to a loosely coupled characteristic of the large air-gap. Therefore, double layer construction of secondary winding, which was divided in half to increase both output current and output voltage was suggested. In addition, the performance of inductive power transformer to alignment condition between the primary power line and the inductive power transformer was verified by computer simulation of 2kW model.