• ETRI Journal
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• v.30 no.6
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• pp.844-849
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• 2008

A new transcutaneous energy transmission (TET) system was developed for transmitting electrical power to an implanted device, such as an artificial heart in a patient's body. This new design can maintain a stable output voltage independent of the load resistance. The system includes a compensation capacitor to reduce energy loss and increase power transfer efficiency. Experimental results show that the output voltage of the receiving coil changes very little as the load resistance varies from 14.8 ${\Omega}$ to 15 $k{\Omega}$, which corresponds to a change in output power from 0.1 to 97 W.

• Journal of electromagnetic engineering and science
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• v.13 no.1
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• pp.8-15
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• 2013

This paper presents a novel design for a simple rectangular ring with an open-ended monopole antenna that is well suited to DCS/PCS/UMTS/WLAN applications for dual-band operations. A microstrip-fed rectangular monopole antenna is first designed and then modified to introduce the rectangular ring with an open-ended antenna and a rectangular slit in the ground plane. Prototypes of the proposed antenna were fabricated and tested. The antenna, resonating at 1,405 MHz and 4,840 MHz, has a -10 dB impedance bandwidth of about 1,695 and 1,530 MHz (1,220~2,815 and 4,495~6,025 MHz), or about 79.06 % and 29.09 %. The observed 2D radiation patterns and 3D gain performance of the antenna in the operation bands are discussed.

• Journal of Electrical Engineering and Technology
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• v.4 no.2
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• pp.277-281
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• 2009

The complex resonant frequency problem of a superconductor patch is formulated in terms of an integral equation which is the kernel of a dyadic Green's function. To include the effect of the superconductivity of the microstrip patch, the surface complex impedance of the superconductor film is introduced using the two fluids model of Gorter and Casimir. The Galerkin procedure is used in the resolution of the electric field integral equation. Numerical results concerning the effect of the operating temperature of a superconductor patch on the characteristics of the antenna are presented.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.501-502
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• 2011

Based on the several advantages of high-temperature superconducting cable, there are many researches about HTS cable. In the aspect of power system engineering, since it has very low impedance, approximately zero, it is profitable for large capacity distribution line into the large scale load. In the step of its verifications, the HTS cable had been installed in Icheon substation and operated. In this paper, the protection coordination for Icheon substation had been designed and verified using PSCAD/EMTDC.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.527-528
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• 2011

송전선로에서 발생하는 고장의 대부분은 낙뢰에 의한 상-대지간 섬락이나 외물접촉, 혹은 애자련의 오손에 의한 절연파괴 등이 대부분이다. 그리고 대분의 고장은 큰 고장전류를 흘리게 되어 보호계전기가 동작하여 고장구간을 신속하게 분리하게 된다. 그러나, 본 고장사례는 매우 희귀한 고장 사례로서, 고저항 아크 지락에 의하여 발생하는 과도회복전압(TRV: Transient Recovery Voltage)이 애자련에 섬락을 일으킨 경우이다. 본 연구에서는 EMTP (Electro-Magnetic Transient Program)를 이용하여 고저항 지락시 아크의 단속에 의하여 과도회복전압이 발생할 가능성이 있음을 보였으며, 고장기록장치(Fault Recorder)에 나타난 파형 기록과의 유사성을 확인하였다. 또한, 고저항 지락에 의하여 직류분이 초기에 방전됨으로써 고장전류 파형에 직류분 오프셋이 나타나지 않게 됨을 밝혔다.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.349-352
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• 1997

The EEG amplifier satisfies high gain, high common mode rejection ratio(CMRR), high input impedance, low thermal drift, low noise and good d.c. performance. The Bipolar amplifier of this paper safisfies above categories and aim at minimization of the ESU(electric surgical unit) interference.

• KIEE International Transactions on Power Engineering
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• v.4A no.1
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• pp.1-5
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• 2004

The model of a power system with load dynamics is studied by investigating qualitative changes in its behavior as the reactive power demand at a load bus is increased. The load is created using induction motors parallel with the constant power and constant impedance load. As the load increases, the system experiences various bifurcations such as sub critical and supercritical Hopf, period-doubling and saddle-node bifurcation. The latter may lead the system to voltage collapse. A nonlinear controller is used to control the subcritical Hopf bifurcation and hence mitigate voltage collapse. It is applied to the KEPCO (Korean Electric Power Company) system to demonstrate its validity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.389-392
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• 2001

In this paper, we have explained electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformer were measured under the various conditions of loads and frequencies. We measured resonant frequency from impedance curve. It was shown from experiments that output voltage has increased and resonant frequency has changed according to various resistor loads. Output current has changed inversely proportional to resistances.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.31-38
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• 2004

PMN-PT, a piezoelectric single crystal, has many useful applications such as sensors and actuators. In this paper, all the elastic, piezoelectric, and dielectric constants of the PMN-32％PT single crystals were measured by the resonance method. For the rhombohedral symmetry, a total of twelve independent material constants were measured such as six elastic compliance constants at constant electric field, two dielectric constants at constant stress, and four piezoelectric constants d. Seven sets of crystal samples of each different geometry were prepared for the measurement of length-thickness extensional, thickness extensional, radial, length extensional and thickness shear modes of vibration, respectively. In order to check the validity of the measurement, experimental impedance spectrum of the PMN-PT crystal was compared with numerical data spectrum calculated with the measured material constants. The good agreement between the two spectra confirmed validity of the results in this paper.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1226-1228
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• 2001

In this paper, the modified simulation algorithms of the Auto Transformer (AT) feeding electric train were proposed. To obtain terminal voltage of train by using equivalent circuit of the AT feeding system, the iterative method is proposed for which determine the train voltages. The train voltages are iteratively calculated from the system voltage drop and line impedance. In the case study, the proposed method is verified from actual operation data of the Kwa-Chon line. Also it is verified that the proposed method can be extent to the multi-train simulation tool. The terminal voltage of the multi-train can be calculated by using superposition principle and it is easily applied to the proposed method. Therefore, the proposed method can be a solution for the complexity of the circuit analysis in the existing methods.