• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.27-30
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• 1991

With the recent development of high performance AC superconducting wire of very small ac loss and large current carrying capacity, the possibility of superconducting air core transformer is being studied. The air core transformer has merits of no iron loss, no insulation to the core and no harmonics. But the air core transformer has large exciting current and low magnetic coupling factor. To increase the coupling factor, the transformer of toroidal shape is proposed and designed. (10KVA, 110/220V) Compared with air core transformer of solenoidal shape, the performance is improved. The exciting current occupies about 22% of the rated current.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.90-94
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• 2000

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 switching inverter-type power supply has been investigated an developed. in recent years. But because of it's additional circuit and devices inverter-type power supply is more expensive than conventional one. In this paper The design procedure of a novel HVC embedded high frequency transformer is proposed for down-sizing and cost reduction. Also transformer equivalent circuit model is derived by FEM analysis and parameter measurements. And the operation of proposed HVC embedded transformer is verified by simulation and experimental results.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.1
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• pp.6-11
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• 2013

In this paper, the temperature characteristics of mold transformer for the distribution power system have been analyzed by using computational fluid dynamics(CFD). The model has been modeled by coil, cores, insulating materials and frames about 3MVA grade mold transformer and analyzed the temperature distribution of the structure with a heat fluid. The fluid, which is incompressible ideal gas, is analyzed as a turbulent flow phenomenon on the assumption that it is natural cooling of transformer cooling system. Through this study, by examining the temperature distribution and hot-spot of the structure field of the mold transformer, cooling design and temperature distribution information, which are demanded for designing are estimated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.70-77
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• 2011

Sewage treatment plants, consuming 1,756[GWh] which is 0.53[%] of national wide electricity consumption, is one of the electricity consuming facilites. At the research of electricity consumption and power quality analysis on sewage treatment plants, average utilization of transformer was less than 40[%] because peak load was very lower than its capacity due to excess capacity. So reduction of power loss can be achieved by transformer design optimization. The achievement in this research, is to meet reduction of power loss through optimizing the capacity and to improve as high efficiency-low loss transformer while the transformer is operating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.198-202
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• 2001

In this study, contour vibration mode piezoelectric transformer with size of 27.5${\times}$27.5${\times}$2.6mm$^3$ using PNW-PMN-PZT ceramic was fabricated. And the piezoelectric transformer was adopted to fluorescent lamp ballast circuit. Electrical characteristics of the piezoelectric transformer were investigated for fluorescent lamp ballast application. The electrical properties and characteristic temperature rise were measured using oscilloscope and infrared temperature sensor. A 28W fluorescent lamp was successfully driven by the fabricated ballast circuit. After driving the lamp using ballast circuit for 24 min, the output power, efficiency and characteristic temperature rise of piezoelectric transformer showed the appropriate values of 28.85[W], 86.3[%] and 15[$^{\circ}C$], respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.350-356
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• 2006

In this study, piezoelectric transformer was manufactured at the sintering temperature of $950^{\circ}C$, and then the feasibility of application to low temperature sintering piezoelectric transformers was investigated by evaluating the electrical characteristics of it. The voltage ratio of piezoelectric transformer showed the maximum value at the resonant frequency of input part, and increased according to the increase of load resistance. The output power and efficiency of piezoelectric transformer showed the superior properties when the output impedance of it coincides with the load resistance. Piezoelectric transformer manufactured at the low temperature of $950^{\circ}C$ showed the heat generation less than $20^{\circ}C$ at the output power of 30 W, and stable driving characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.680-683
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• 2001

The output characteristics of step-down piezoelectric transformer is changed by a structure of layers. In this paper, we simulated output characteristics of multi-layer piezoelectric transformers with variation of output layers. Also, fabricated piezoelectric transformers were compared with simulated data. From simulated piezoelectric transformers, the output voltage decreased with increasing number of layers. From these results, piezoelectric transformers were made and the output electrical power of the transformers was measured at resonance frequency and at other frequency. The electrical power of transformers was measured on each transformer's resonance mode. However, measured value of 12-layed transformer's output power was smaller than that of 6-layered transformer's one. It is supposed that internal capacitance and reactance of the piezoelectric transformer's were effected in this result. Therefore we need to connect other road resistance and capacitance in output circuit, in order to increase electrical power of transformers.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.208-209
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• 2006

Voltage Transformer is used to transform high voltage into low voltage to input signal of protection relay. Most of the Voltage Transformers use the iron core which maximizes the flux linkage. The ratio of the Voltage Transformer depends on the transformer turns ratio. The current which flows in the Voltage Transformer has non-linear characteristic caused by hysteresis of the iron core, it causes a voltage loss in the winding impedances which makes measurement errors. This paper describes an error compensation method considering hysteresis characteristic. The proposed compensation method improves error by calculating the primary current from the exciting current of the hysteresis loop in the Voltage Transformer, compensating the voltage loss.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.184-186
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• 2009

In past, transformer connection study was concentrated on efficiency improvement and life time broadening. But environmental side began to become important recently. In existing, quick transaction of mineral oil used to insulation oil of transformer is possibility to be difficult and causes environmental pollution in case of was outpoured and there is worry of fire occurrence. Accordingly, nonflammable performance becomes many interest in excellent vegetable oil because ignition point is high than mineral oil and environment friendly material. But, vegetable oil is cooling of transformer and insulation problem of insulating paper for cause of insulation oil special quality. Therefore, in this paper, special quality of vegetable oil that there are being a lot of mineral oil and the latest interest examined about problem and consideration item to be solved to analyzed comparison and applies vegetable oil to transformer for electric power.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.1
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• pp.17-21
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• 2005

AC loss is one of the important parameters in HTS (High Temperature Superconducting) AC devices. Among the HTS AC power devices, the transformer is the essential part in the electrical power system. But unfortunately, the transformer is the worst HTS device concerning AC loss because of very large magnetization loss due to high magnetic field applied to the HTS wire. We calculated the magnetization losses in HTS pancake windings for transformer according to the operating temperature. Two kinds of arrangement of HTS pancake windings were adopted for calculation of AC losses of a shell type transformer, and the analysis results were presented and discussed.