• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.6
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• pp.304-308
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• 2002

We demonstrate a simple pulsed $CO_2$ laser with millisecond long pulse duration in a tube at a low pressure of less than 30 Torr. The novel power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply doesn't need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. To control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of SCR(Silicon Controlled Rectifier) gate is varied from 30。 to 150。. A ZCS (Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control precisely the gate signal of the SCR. The maximum laser output of 35 W is obtained at a total pressure of 18 Torr, a pulse repetition rate of 60 Hz, and a SCR gate firing angle of 90。 . In addition, the resulting laser pulse width is approximately 3㎳(FWHM). This is a relatively long pulse width, compared with other repetitively pulsed $CO_2$ lasers.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.456-458
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• 1995

This paper describes a diagnosis of power transformers by on-line detection of ultrasonic signals. Partial discharge in power transformer generates ultrasonic signals. The trend of the ultrasonic signal number can be measured when partial discharge is generated in HV Winding. The trend of the ultrasonic signal number could easily be distinguished by taking moving average. The insulation failure due to partial discharge in transformers can be predicted based in the trend analysis of the number of ultrasonic signals caused by partial discharge.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1142-1147
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• 2002

For the evaluation of the DC motor noise and vibration, usually it is rely on human feeling because some kinds of noise are not definitely represented by measurement Instrument such as sound meter. But when we consider time signal of the noise and vibration. It is possible to represent them. And in this paper. it is suggested to study output current shape of the motor because it Is the source to make speed and torque variation of the motor. If the current shape is not stable. it makes operating state of the motor unstable and produces noise and vibration. By analyzing signal at time and frequency of noise and vibration and current shape. it is possible to automation of the noise and vibration measurement in the Production line.

• Journal of Power Electronics
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• v.6 no.2
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• pp.139-145
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• 2006

This paper describes the ultra precise position estimation of a servomotor using a sinusoidal encoder based on Arcsine Interpolation Method for the cost reduction of circuit design. The amplitude and offset errors of the sinusoidal encoder output signals, from the encoder itself and analog signal processing procedures, are effectively compensated and on-line tuned by utilizing a low cost programmable differential amplifier without any special expensive equipment. For a theoretical evaluation of the practical resolution of this system, the relationship between the amplitude of ADC(Analog to Digital Converter) input signal errors and the anticipated resolution is also addressed. The performance of the proposed method is verified by comparing it with speed control characteristics of the servomotor driving system using a digital incremental 50,000ppr encoder in the experiments.

• Journal of Power System Engineering
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• v.10 no.4
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• pp.165-171
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• 2006

An experiment to observe reduction of pressure fluctuation in the compressing system utilizing snubber has done. The experiment measured pressure at inlet and outlet of snubber. It used an air compressor as a model of hydrogen one. Snubber with buffer and snubber without buffer were used to get comprehensive comparison between both of that snubber. An analysis by using Fast Fourier Transform (FFT) method was conducted to verify working pressure frequency. With this method pure signal of static pressure was filtered from noisy signal. The experiment was run for several speeds of piston movement. It was controlled by adjustable frequency regulator that controled rotation of actuator motor. This was connected to the piston-reciprocating compressor with V-belt. From result obtained, the fluctuation was increasing proportionally when frequency of driver motor was increased.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.155-159
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• 2001

In this paper, an on-line dead-time compensation method based on a time delay control approach is presented. The disturbance voltages caused by the dead time are estimated in an on-line manner by the time delay control without any additional circuits and off-line experimental measurements. And the estimated disturbance voltages are fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.25-29
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• 2010

Safety of railroad is result of reliability which is received from test & evaluation of system. Railroad system is consisted of various sub system such as vehicle, supply of electric power, signal, communication, rail track construction, operation. To secure safety of railroad, evaluation about parts, assembly, sub system, whole system etc.. that compose railroad is essential. In this paper, I wish to describe for results that analyze korean tilting vehicle's derailment coefficient developed by national research achievement. Confirmed that is possible even if speed up, curved line department running speed that estimate korean tilting vehicle's running safety in curved line track of Jungang Line about 20 km/h than present operating speed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.346-346
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• 2009

저손실 고투자율 특성을 갖는 $\alpha$-Fe 나노결정 자심재료를 제조하기 위해 열처리 온도를 변화시켰으며 투자율과 신호전송 특성을 측정한 결과 $510^{\circ}C$에서 열처리된 자심재료에서 가장 우수한 특성을 얻었다. 저주파 대역에서의 신호전송 특성은 자심재료의 자기적 특성에 지배적인 영향을 받으며, 고주파 대역의 신호전송 특성은 임피던스 매칭으로 향상시킬 수 있었다. 에어-캡은 $500{\mu}m$ 이상 적용할 때, 100 A이상까지 안정적인 특성을 발휘하였다. 그리고 고역통과 필터의 설계와 신호결합장치에의 적용을 통해 통신대역 이외의 노이즈를 제거할 수 있었다.

• Journal of Power Electronics
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• v.7 no.4
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• pp.271-277
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• 2007

In this paper, an induction motor rotor fault diagnosis system using current signals, which are measured using the axis-transformation method is presented. Inverter-fed motor drives, unlike line-driven motor drives, have stator currents which are rich in harmonics and therefore fault diagnosis using stator current is not trivial. The current signals for rotor fault diagnosis need precise and high resolution information, which means the diagnosis system demands additional hardware such as a low pass filter, high resolution ADC, an encoder and additional hardware. Therefore, the proposed axis-transformation method is expected to contribute to a low cost fault diagnosis system in inverter-fed motor drives without the need for any additional hardware. In order to confirm the validity of the developed algorithms, various experiments for rotor faults are tested and the line current spectrum of each faulty situation, using the Park transformation, is compared with the results obtained from the FFT(Fast Fourier Transform).

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.693-696
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• 1999

This paper describes a new voltage recorder for the voltage management of a power distribution line by using a new voltage measurement technique. The RMS(Root Mean Square) voltage measurement for the power line under the assumption of a sinusoidal input voltage is taken by the full-wave rectifier, half-adder utilizing operational amplifier(OP) circuit. A/D converter utilizing a dual slope converter converts an analog voltage signal into a serial pulse. The pulse is counted with a single chip micro-controller, converted with the RMS voltage, and saved into a flash memory. In the last, a new voltage recorder with compact size and multifunction is developed. Also, Voltage Management System that can analyze the stored data via RS-232C cable is developed based on Windows 95 and Visual C++.