• Proceedings of the KIEE Conference
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• 2004.11d
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• pp.63-66
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• 2004

It is widely known that the ultra high frequency (UHF) method that detects the electromagnetic wave of the PD pulses in the gas insulated space is one of the most competitive methods for its high sensitivity. From the above point of view, this paper describes the characteristics of GIS PD signals measured with ultra wide band (UWB) GIS PD defecting system in which PD signals are defected into the dual UHF band. Thc UWB PD detection system consists of the UWB UHF coupler, the UWB low noise amplifier (LNA) and the oscilloscope. The dual bands for PD signals are 0.5-2GHz(full band) and 1-2GHz(high band). As results, it was found that the partial discharges of each defect have their own characteristic pattern and the ratio of High hand to Full band increases with gas pressure.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.214-220
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• 2008

Most of converter system could obtain almost unity power factor and make input current sinusoidal waveform, but they have many problems, such as electromagnetic interference and switching losses caused by switching noise in main switch. To solve these problems in hard switching PFC converter, soft switching converter using a resonant between capacitor and inductor is invented In this paper, advantages and disadvantages of conventional ZVT(Zero-Voltage-Transition) soft switching converter using a auxiliary resonant circuit is discussed. Then Improved ZVT soft switching converter proposed. This improved ZVT converter's operation principal, specific property, design scheme of main are described. From Simulation and experiment results of conventional ZVT soft switching and improved ZVT soft switching converter with active snubber, characteristics of the converter are confirmed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.9-14
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• 1998

One of the areas in the continuous casting process that up to this point, has not been definitively instrumented is a method of reliably locating the part of a continuously cast strand that remains liquid for a period after the outer portion has solidified. To solve the problem. Electromagnetic Trandsducers(EMAT) which operate across an air gap without the need for a coupling medium has been developed. The system was designed to employ a through transmission technique which enhanced the signal-to-noise ratio. The Al 75$\times$75mm and 75$\times$100mm simulators with 2, 4, 8, 16, 32 mm hole respectively has been produced in order to verify the developed EMAT system and to measure to liquid core in continuous casting strand. The system developed can be employed for the optimization of torch cutting speed and for the final cut length of the bloom as well as calculation of average bloom temperature.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.455-462
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• 2003

Switching PFC converters are widely used not only to comply the power quality specification but also for maximum efficiency. However switching PFC converters generate serious electromagnetic interference(EMI). In this paper to solve this problem, we applied the APW(Anti-Phase Winding) and RPWM(Random PWM) technique to PFC boost converter and obtained good results. Simulation and experimental results show the improved harmonics and reduced EMI effect in air-conditioner system.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.494-497
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• 2002

Conducted electromagnetic interference (EMI) from switch mode power supplies (SMPS) has become a major problem due to the proliferation of these devices employing dc-dc converters using standard pulse width modulation (PWM). In this paper, we proposed the sigma-delta modulation $({\sum}{\Delta}M)$ as an alternative switching technique to reduce the conducted EMI in SMPS. A comparative investigation on conducted EMI generated by PWM and ${\sum}{\Delta}M$ techniques are experimentally performed on a 300W Boost converter.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.793-797
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• 2003

Switching PFC converters are widely used not only to comply the power quality specification but also for maximum efficiency. However switching PFC converters generate serious electromagnetic interference (EMI). In this paper to solve this problem, we applied the APW(Anti Phase Winding) and RPWM(Ran-dom PWM) technique to PFC boost converter and obtained satisfactory results. Simulation and experimental results show the improved harmonic and reduced EMI effect in air-conditioner system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.410-413
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• 2001

In this paper, we present results of this that design of the multi-layer VCO(Voltage Controlled Oscillator), which is composed of the resonation circuit and the oscillation circuit, using EM simulator and nonlinear RF circuit simulator. EM simulator is used for acquiring EM(Electromagnetic) characteristics of conductor pattern as well as designing multi-layer VCO, Acquired EM characteristics of the circuit pattern was used like real components at nonlinear RF circuit simulator. Finally VCO is simulated at nonlinear RF circuit simulator. The material for the circuit pattern was Ag and the dielectric was DuPont #9599, which is applied for L TCC process. The structure is constructed with 4 conducting layer. Simulated results showed that the output level was about 1[dBm], the phase noise was 102 [dBc/Hz] at 30[kHz] offset frequency, the harmonics -8dBc, and the control voltage sensitivity of 30[MHz/V] with a DC current consumption of l0[mA]

• Journal of KSNVE
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• v.5 no.1
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.39-46
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• 1998

For permanent magnet brushless DC motors used for high speed fuel pumps, torque ripple is an important origin of vibration, acoustic noise and speed fluctuation. In this paper, the output torque profile of a PM motor with one phase energized is decomposed into the commutation torque, the reluctance torque and the armature reaction torque according to their source origins. It verifies that the output torque profile is qualitatively equivalent to the BEMF profile for low reluctance motors. This paper discusses the effect of magnet pole shaping and magnet arc length on the output torque and torque ripple. A magnet edge shaping is proposed to design a trapezoidal BEMF motor without torque ripple, with minimal sacrifice of the maximum output torque.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.766-768
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• 1998

Optical Temperature Distribution measurement System (OTDS) is completely different from conventional electric point sensor in that it uses the optical fiber itself as the sensor. This new concept in temperature measuring system requires only one fiber to be laid. The use of optical fiber also gives the advantage of small diameter, light weight, explosion resistance, and electromagnetic noise resistance. The OTDS is a sensor which is capable of making a precise measurement over a wide range of areas using only a single optical fiber. Since current temperature sensors, such as the thermocouple, are only used to measure temperaturea of point, they are almost impractical for measuring a wider range because of the extremely high cost. In comparision with current sensors, the optical fiber distributed temperature sensor can make much quicker and more precise measurements at a comparatively low cost.