• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.255-258
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• 1998

In this paper. we designed and simmulated a ring-dot type piezoelectric transformer. As the result, piezoelectric transformer of 25${\times}25{\times}3.5mm$ size (Dot electrode diameter of Ilmm) show the maximum displacement, stress and output power. When the Input voltage of piezoelectric transformer was 155V. Output voltage show 30V and output power 9W at the load resistance of $100\Omega$

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.295-300
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• 2007

High temperature superconducting (HTS) windings for an HTS transformer which have been developed have two kinds of type, one is the layer winding and the other is disk winding. The layer winding has adopted for an HTS power transformer so far because of the small AC losses of the HTS windings. The disk windings have surface of the HTS wire. We propose a new winding method for a high voltage HTS transformer which has advantages of both type of HTS windings, and we call it continuous disk winding. This new HTS winding consists of pile of HTS disk windings. The continuous disk winding was fabricated with multi-stacked HTS wires for dover HTS transformer. We can check the potential possibility from the characteristic test of the fabricated winding. The new type HTS windings can be applied to HTS power transformers, especially to the high voltage ones.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.293-296
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• 2001

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 inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, The design procedure of a novel HVC embedded high frequency transformer is proposed for down-sizing and cost reduction of Inverter-type power supply. Also, equivalent circuit mode] is derived by FEM analysis and impedance measurements. And the operation of proposed HVC embedded transformer is verified by simulations and experimental results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.171-177
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• 2004

Voltage step-down characteristics in Ring/Dot type piezoelectric transformer were examined as a function of the area of input electrode when the area of output electrode is fixed. The effects of driving frequency and load resistance on the voltage step-down characteristics were also examined. Voltage gain was greatly dependent on the driving frequency and load resistance, and showed a maximum gain at resonance frequency of the step-down transformer. The frequency where the maximum cutout voltage appears increased about 0.2％ as the load resistance increased from 10 to 150 Ω. As the area of input electrode increased, the voltage gain and the efficiency of the transformer increased. Frequency dependence of efficiency of the step-down transformer revealed a similar tendency with the voltage gain curves. The maximum efficiency remarked 94% when the input voltage and the load resistance were 20 Vpp and 120 Ω, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.722-725
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• 2004

Voltage step-down characteristics in Ring/Dot type piezoelectric transformer were examined as a function of the area of input electrode when the area of output electrode is fixed. The effects of driving frequency and load resistance on the voltage step-down characteristics were also examined. Voltage gain was greatly dependent on the driving frequency and load resistance, and showed a maximum gain at resonance frequency of the step-down transformer. The frequency where the maximum output voltage appears increased about 0.2% as the load resistance increased from 10 to $150\Omega$. As the area of input electrode increased, the voltage gain and the efficiency of the transformer increased. Frequency dependence of efficiency of the step-down transformer revealed a similar tendency with the voltage gain curves. The maximum efficiency remarked 94% when the input voltage and the load resistance were 20 $V_{PP}$ and $120\Omega$, respectively.

• Progress in Superconductivity and Cryogenics
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• v.19 no.2
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• pp.44-47
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• 2017

In this paper, the current limiting characteristics of the transformer type superconducting fault current limiter (SFCL) with the two coupled secondary windings due to its winding direction were analyzed. To analyze the dependence of transient fault current limiting characteristics on the winding direction of the additional secondary winding, the fault current limiting tests of the SFCL with an additional secondary winding, wound as subtractive polarity winding and additive polarity winding, were carried out. The time interval of quench occurrence between two superconducting elements comprising the transformer type SFCL with the additional secondary winding was confirmed to be affected by the winding direction of the additional secondary winding. In case of the subtractive polarity winding of the additional secondary winding, the time interval of the quench occurrence in two superconducting elements was shorter than the case of the additive polarity winding.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.10
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• pp.630-634
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• 2016

In this paper, we analyzed the power consumption and the accumulated energy in HTSC (high-TC superconducting elements) according to the resistance of HTSC element and the winding current of transformer type SFCL (superconducting fault current limiter) using double quench. For the analysis, two different inductances of the one secondary winding among two secondary windings comprising the transformer type SFCL were selected and the short-circuit tests were carried out. The consumed power and the accumulated energy in HTSC element connected into the secondary winding with larger inductance were analyzed to be larger compared to the one connected into the secondary winding with lower inductance.

• 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 ${\pm}4.45%$

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.301-308
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• 2011

This paper deals with the coupled electromagnetic-mechanical field analysis for short-circuit electromagnetic force of the dry-type transformer. The short-circuit currents are calculated using external circuit in accordance with short-circuit test equipment. According to short-circuit current, the generated magnetic leakage flux density in dry-type transformer model is calculated by finite element method. The radially-directed electromagnetic forces in windings are calculated using electromagnetic field analysis and then axially-directed electromagnetic forces in windings are calculated using electromagnetic-mechanical field analysis. The calculated axially-directed electromagnetic forces in high voltage winding are compared to those of measured ones and showed good agreement with experimental results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.2090-2091
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• 2007

We investigated the characteristics of transformer type SFCL with neutral line. The transformer type SFCL having neutral line has achieved the simultaneous quench because the secondary winding has acted as parallel reactor. The fault current of SFCL was limited according to ratio of turn number between primary and secondary windings. Therefore, the power burden of superconducting element can be reduced by reduction of ratio of turn number between primary and secondary windings. As a result, we could expect reduction of it's volume in the transformer type SFCL.