• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.101-103
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• 2018

This paper describes -40kV high voltage solid state pulse power modulator (SSPPM) for driving a magnetron, which is used as a RF power source of LINAC for cancer treatment systems. In case of the medical LINAC, small size and light weight are required. The SSPPM is 92 liters in size and weighs 50 kg. In this paper, S-band 2.6 MW magnetron load experiment is conducted and impedance matching was applied to obtain a smooth output current. Finally, the experimental results is discussed and the reliability of SSPPM is verified.

• Journal of Power Electronics
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• 제19권2호
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• pp.560-568
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• 2019

This paper studies the inherent relationship between currents and zero-sequence components. Then a precise algorithm is proposed to calculate the injected zero-sequence component to control the DC-Link neutral-point voltage balance, which can result in a more efficient and flexible neutral point voltage balance with a desirable performance. In addition, it is shown that carried-based PWM with the calculated zero-sequence component scheme can be equivalent to space-vector pulse-width modulation (SVPWM). Based on the proposed method, the optimal zero-sequence component of the feasible modulation indices is analyzed. In addition, the unbalanced load limitation of the DC-Link neutral-point voltage balance control is also revealed. Simulation and experimental results are shown to verify the validity and practicality of the proposed algorithm.

• 한국정밀공학회지
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• 제17권4호
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• pp.220-225
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• 2000

This paper develops a finite element model for studying occupant behavior of a mid-size truck equipped with a driver side airbag. The developed model simulates an occupant behavior using PAM-CRASH/PAM-SAFE in super computer SP2. The model is developed based on a sled test. A 50% hybrid dummy III is used for measuring head and chest accelerations and femur loads, and major injury coefficients such as HIC, CA and femur load. Inferior components such as foot rest, seat, kneebolster, crash pad, etc. are roughly modeled and defined by a rigid material model. And contact type II is used for detecting a contact with dummy. Contact type II definition uses force-deflection relationship of each body Such components as steering column which directly affect on the occupant injuy are modeled in detail and defined by an elastic-plastic material model. Airbag cushion is modeled using rivet elements. Airbag cover groove is modeled using rivet elements. Airbag tether is modeled as nonlinear bar elements. Airbag model has two vent holes to ventilating the exploded gas. Airbag is folded close to the real airbag folding procedure, and folded cautiously in order not to have initial penetration. A vehicle pulse acquired from 31mph frontal barrier test is used as input signal for the simulation. The simulation conditions are tuned to the sled test ones. The measured dummy accelerations and major injury coefficients, and filmed dummy behavior and airbag inflation process using high speed camera are compared to the simulation results to verify the developed finite element model.

• 전력전자학회논문지
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• 제19권5호
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• pp.399-406
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• 2014

This study investigates the structure and operation of the ITER VS converter and proposes a sequence control method for six series-connected VS converters to reduce reactive power. The operation and the proposed sequence control method are verified through RTDS simulation. The ITER VS converter must supply voltage/current to the superconducting magnets for plasma current vertical stabilization, and the four-quadrant operation must proceed without a zero-current discontinuous section. The operation mode of the VS converter is separated into a 12- and 6-pulse circulating current and transition modes according to the size of the load current. The output voltage of the unit VS converter is limited because of the rated voltage; however, the superconducting coil must increase the operating output voltage. Thus, the VS converter must be connected in a 6-series to provide the required operating output voltage. The output voltage of the VS converters is controlled continuously; however, reactive power is limited within a minimized value of the grid. In this study, the unit converter is compared with converters connected in a 6-series to determine a suitable sequence control method. The output voltage is the same in all cases, but the maximum reactive power is reduced from 100% to 73%. This sequence control method is verified through RTDS simulation.

• Journal of Power Electronics
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• 제18권5호
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• pp.1336-1346
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• 2018

Wide band gap semiconductor devices such as SiC MOSFETs are becoming the preferred devices for high frequency and high power density converters due to their excellent performances. However, the proportion of the switching loss that accounts for the whole inverter loss is growing along with an increase of the switching frequency. In view of the third quadrant working characteristics of a SiC MOSFET, synchronous rectification discontinuous pulse-width modulation is proposed (SRDPWM) to further reduce system losses. The SRDPWM has been analyzed in detail. Based on a frequency domain mathematical model, a quantitative mathematical analysis of the harmonic characteristic is conducted by double Fourier transform. Meanwhile, a switching loss model and a conduction loss model of inverter for SRDPWM have been built. Simulation and experimental results verify the result of the harmonic analysis of the double Fourier analysis and the accuracy of the loss models. The efficiencies of the SRDPWM and the SVPWM are compared. The result indicates that the SRDPWM has fewer losses and a higher efficiency than the SVPWM under high switching frequency and light load conditions as a result of the reduced number of switching transitions. In addition, the SRDPWM is more suitable for SiC MOSFET converters.

• 한국진공학회지
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• 제15권3호
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• pp.314-324
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• 2006

KSTAR ICRF 안테나의 진공특성을 실험적으로 조사하였다. 제작된 안테나를 총 유효배기속도 1015 l/s의 진공펌프가 장착된 시험용 진공용기에 설치하였으며, 고주파 시험하기 전에 시간에 따른 압력 변화, 총기체 부하, 도달 진공도 등을 측정하였다. 낮은 출력의 고주파를 반복적으로 인가함으로서 세정 효과를 확인하였다. 안테나에 고주파를 인가하여 시험하는 동안 진공도 변화를 측정하였으며, 압력 상승에 의해 방전이 유발되는 한계 압력을 조사하였다. 본 안테나의 경우 고주파 인가 중에 진공용기의 압력이 $10^{-4}$ mbar 이상이 되면 방전이 일어났다. 장펄스 시험에서 안테나의 온도와 시험용 진공용기의 압력을 측정하여 안테나를 냉각하지 않은 상태에서 운전이 가능한 전압을 조사하였으며, 냉각했을 때의 결과와 비교하였다.

• 한국방사선학회논문지
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• 제4권3호
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• pp.31-37
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• 2010

본 논문에서는 태양광 발전시스템을 이용한 PWM(Pulse Width Modulation) 전압형 인버터를 전력변환기로 구성하였고, 안정된 변조를 위해서 동기신호와 제어신호를 56F8323 마이크로프로세서에 의해서 처리하였다. PWM 전압형 인버터는 태양전지가 연속 발전할 수 없는 단점을 보완하기 위해 일반 상용전원과 연계함으로써 약 10~20[%]의 전력 절감 효과를 얻을 수 있는 에너지 절약 전원 복합형 전력변환장치로 구성하였다. 그리고 PWM 전압형 인버터와 위상동기를 위해서 계통전압을 검출하고 계통전압과 인버터 출력을 동상 운전하므로 잉여전력을 계통과 연계할 수 있게 하였다. 또한, 고조파를 절감한 출력을 유지함으로써 부하와 계통에 전력이 안정하게 공급될 수 있도록 제어 시스템을 적용하여 좋은 결과를 얻을 수 있었다.

• 한국안전학회지
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• 제32권5호
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• pp.62-68
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• 2017

It is necessary to analyze on the compressive strength among material properties of concrete for confirming damages of architectures due to large explosion. A non destructive test is known as the representative methods estimating compressive strength and ultrasonic pulse velocity, rebound hardness test are widely used because of their simplicity, convenience. But combined method supplementing two types is applied at now as they are affected by the characteristics of test specimen. In this research to check damages on the members of structure before and after explosion, the characteristics of compressive strength are compared and analyzed through a real explosion test prior to full scale structures. The test results showed that the larger the TNT powder and the shorter the distance, the greater the decrease in strength before and after the explosion and that the largest displacement and moment for the explosive load and the greatest decrease in the strength at the central part. Due to the surface condition and the thickness variation of the concrete specimens, the standard deviation value is the smallest in the combining method of fusion of the ultrasonic method and rebound hardness method. Thus, the combining method can be one of appropriate methods to evaluate the strength in the reinforced concrete structures damaged by the explosion.

• 동의생리병리학회지
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• 제16권3호
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• pp.609-615
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• 2002

A medical treatment of alternating current high-voltage electric field therapy is a method in which we get a healing effect, applying electric field to an organism through an artificial device. In order to estimate the clinical effects of alternating current high-voltage electric field load(HEALTHTRON) on the rehabilitation of stroke patients, improvement of a peripheral blood circulation, and psychogenic symptom, we used BEUNZEUNGHEYNG Instrument, NIHSS(the National Institutes of Health Stroke Scale), FIM(Functional Independence Measure)lnstrument to research BEUNZEUNGHEYNG and recovery of rehabilitative funation. and also we used Thermography, Pulse Meter to measure body temperature and pulse, blood elements, and neuro modulators. We have reached the following conclusions after researching the clinical effects of alternating current high-voltage electric field therapy on the recovery of rehabilitative function and peripheral blood circulation. 1. HEALTHTRON efficiently has increased the volume of peripheral blood circulation in stroke patients. 2. HEALTHTRON rapidly has treated the symptoms of sleeplessness, alertness, and dizziness of stroke patients. 3. HEALTHTRON rapidly has improved rehabilitative function of stroke patients and the adjustment to their activities.

• 전력전자학회논문지
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• 제16권6호
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• pp.610-617
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• 2011

본 논문은 공간벡터펄스 변조법(SVPWM, Space Vector Pulse Width Modulation)을 사용하는 3상 인버터의 새로운 데드타임 직접 보상 방법을 제안한다. 제안된 데드타임 보상방식은 인버터에 인가되는 데드타임을 중간상 전류의 방향에 따라, 유효전압이 인가되는 유효전압벡터 인가시간에서 직접 보상하는 방식이다. 3상 인버터에서 각상에 인가되는 전압의 크기는 유효전압이 인가되는 시간에 의해 결정되고, 데드타임의 영향에 따라, 실제로 유효전압이 인가되는 스위칭 시간은 전류의 방향에 따라 손실이 발생하게 된다. 제안된 방식에서는 실제로 전류의 방향에 따라 손실이 발생하는 유효전압벡터의 인가시간에 직접적으로 손실 시간을 더하여 유효전압벡터의 인가시간을 계산하는 방식으로 별도의 전압오차를 보상하기 위한 제어기와 복잡한 d-q 변환을 필요로 하지 않는 장점이 있다. 제안된 방식은 3상 R-L 부하에 대하여 컴퓨터 모의해석과 실험을 통하여 제안된 방식의 데드타임 보상을 검증하였다.