• 전기의세계
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• v.18 no.2
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• pp.7-14
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• 1969

From the first customer located right at the substation to the last customer at the end of the line, voltage must be held within close limits, so the voltage regulation is more important than the thermal limit. On a typical distribution system during the peak load period, the voltage drop may be serious enough to cause unsatisfactory operation of home appliances in the residential area, and present many problems to manufacturing industries, where the voltage must be maintained within close limits to insure smooth operation. Among all the factors contributing to voltage drop in the distribution system, the voltage drop in the distribution transformer may account for 30% of this figure. If we can eliminate this factor, the power companies can provide better quality electricity to more customers with the existing distribution facilities, thus saving on initial investment costs. Taking all these problems into consideration, the author undertook the design of a capacitive transformer which would give zero voltage drop at rated load and at 80% lagging power factor while incorporating overload features to withstand 400% overload for at least 100 seconds. The following are the results obtained through design, manufacture and test of an initial experimental transformer built with these specific purposes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.177-181
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• 1998

In this paper, we used the $BaTiO_3$ system ceramics with high temperature stability for high voltage devision, and rosen type-piezoelectric transformer for high voltage measurement. when Line-high voltage is 13,20O[V], Input voltage of piezoelectric transformer type-actuator is about 390CV1, and output voltage of it is 26.5FVI on the no-load. And also, temperature stability from >$-25^{\circ}C$ to >$50^{\circ}C$ is less than ${\pm}4.45%$

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1414-1415
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• 2007

200 kV AC high voltage national standard system has been established with a purpose for support of heavy electrical industry. The system consists of high AC voltage source and regulating unit, the standard voltage transformer, voltage transformer comparator, and voltage transformer burden, and voltage transformer under test.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.706-709
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• 1992

This paper deals with the operation of a parametric transformer through the normalization of system equations. Based on these equations, the effects of excitation voltage waveforms on the performances of the parametric transformer are analyzed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1543-1550
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• 2015

Ferroresonance is a non-linear vibrational phenomenon that is generated by the electrical interaction of the inductance component with the capacitor component of a certain capacitance as the device of the inductance component such as a transformer is saturated due to the degradation, the waveform distortion of current and voltage, and the oscillation of overcurrent and overvoltage in a system. Recently, ferroresonance was generated from the waveform distortion of current and voltage, or the overvoltage or undervoltage phenomenon caused by the nature of an electrical power system and design technology of the transformer in the three phase transformer system. Hence, in general, ferroresonance analyzed by converting to the LC equivalent circuit. However, in general, the aforementioned analytical method only applies to the resonance phenomenon that is generated by the interaction of the capacitance of bussbar and grounding, and switching as the capacitor component with PT and the transformer as the inductance component in a system. Subsequently, the condition where ferroresonance was generated since overvoltage was supplied as line voltage to the phase voltage and thus the iron core is saturated due to the interconnection between grounded and ungrounded systems could not be analyzed when single phase PT was connected in a ${\Delta}$/Y connection system. In this study, voltage swell in the configuration of grounded circuit of a step-up transformer with the ${\Delta}-{\Delta}$ connection linked to PT for control power and the ferroresonance generated by overvoltage when the line voltage of the ${\Delta}-{\Delta}$ connection was connected to the phase voltage of the grounded Y-Y connection were analyzed using PSCAD / EMTDC through the failure case of the transformer caused by ferroresonance in the system with the ${\Delta}-{\Delta}$/Y-Y connection, and subsequently, the preventive measure of ferroresonance was proposed.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.5
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• pp.411-416
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• 2010

A voltage drop characteristics of a transformer-based voltage disturbance generator with series transformers is analysed. It is well known that a voltage disturbance generator with series transformer is cost-effective and reliable compared with other types. The voltage drop depends on the %Z of the transformer, power rating, and output power factor. A wrong design of the transformer results in a severe voltage drop, which can not guarantee the proper performance of the generator. The voltage drop is analysed under the condition of 10kVA output power rating and 4% of %Z with the variation of power factor. It is found through simulations and experiments that the drop increases as the power factor decreases in lagging mode, and the drop is 4% of the rated voltage in case of 0.85 lagging power factor.

• 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.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.261-268
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• 2020

Transformer saturation in full bridge (FB) isolated DC-DC converters is caused by uneven switching speeds and voltage drops in semiconductor devices and mismatched gate signals. In order to prevent transformer saturation, most popular and widely used approach is to insert a capacitor in series with the transformer windings. This study conducts extensive analyses on transformer saturation and the effect of DC blocking capacitors when they are placed in the primary or secondary windings of a transformer. The effect of the DC blocking capacitors is verified in voltage-fed and current-fed FB converters.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.138-139
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• 2008

An iron-cored voltage transformer(VT) is usually used to obtain the standard low voltage signal for protection and measurement. Generally, the iron-cored transformers have errors due to the hysteresis characteristics of the iron-core. An error compensating algorithm for iron-cored instrument transformer can improve the accuracy of conventional voltage transformers. This paper describes the iron-cored electronic voltage transformer having the error compensating algorithm. The innovative product composes an iron-cored VT and an intelligent electronic device(IED) having the error compensating algorithm. The test results of the iron-cored electronic voltage transformers in Korea Electro-technology Research Institute(KERI) are presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1745-1750
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• 2017

Starting from the distribution transformer, the insulation oil for the oil immersed power transformer is being used to convert the vegetable oil from the existing mineral oil. Vegetable oil is better in temperature characteristics and insulation performance, is not toxic, and has better biodegradable characteristic than that of mineral oil. In order to investigate the corona inception voltage and dieclectic charateristics of the two insulating oils, three oil immersed transformers using mineral oil and vegetable oil were made and thermal cyclic aged. In this paper, the changes in the corona discharge inception voltage, chemical and electrical properties of the two sampled insulating oils from the transformers had been studied.