• 전력전자학회논문지
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• 제27권2호
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• pp.157-164
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• 2022

This study proposes an enhanced quadruple-Active-Bridge (QAB) converter that can solve power coupling problems. By adopting a multiple winding transformer, the equivalent circuit of a conventional QAB converter has power couplings between arbitrary output ports. This coupling is an unintended power relationship that complicates the regulation of output voltage of the multiple ports. The proposed converter can carry out power decoupling by changing the arrangement of the coupling inductor. Power transfer equations for the proposed converter and its operating principles are analyzed in detail. The power coupling caused by the transformer's leakage inductance is verified by using a proposed coupling factor that presents the relationship between inductance ratio and coupling power. In addition, the decoupling power control performance of the proposed converter is verified by simulation and a 3 kW prototype converter.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.78-82
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• 2014

Power Transformers with more than one secondary winding are not uncommon in industrial applications. But new classes of applications where very large number of independent secondaries are used are becoming popular in controlled converters for medium and high voltage applications. Cascade H-bridge medium voltage drives and Pulse Step Modulation (PSM) based high voltage power supplies are such applications. Regulated high voltage power supplies (Fig. 1) with 35-100 kV, 5-10 MW output range with very fast dynamics (${\mu}S$ order) uses such transformers. Such power supplies are widely used in fusion research. Here series connection of isolated voltage sources with conventional switching semiconductor devices is achieved by large number of separate transformers or by single unit of multi-secondary transformer. Naturally, a transformer having numbers of secondary windings (~40) on single core is the preferred solution due to space and cost considerations. For design and simulation analysis of such a power supply, the model of a multi-secondary transformer poses special problem to any circuit analysis software as many simulation softwares provide transformer models with limited number (3-6) of secondary windings. Multi-Secondary transformer models with 3 different schemes are available. A comparison of test results from a practical Multi-secondary transformer with a simulation model using magnetic component is found to describe the behavior closer to observed test results. Earlier models assumed magnetising inductance in a linear loss less core model although in actual it is saturable core made-up of CRGO steel laminations. This article discusses a more detailed representation of flux coupled magnetic model with saturable core properties to simulate actual transformers very close to its observed parameters in test and actual usage.

• 센서학회지
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• 제10권4호
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• pp.266-272
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• 2001

자동차 엔진오일의 열화상태를 직접 in situ로 측정할 수 있는 코일형 전기용량 센서를 개발하였다. 엔진 오일팬의 드레인 홀의 제한된 공간 속에서 10 pF 이상을 얻기 위하여 코일형으로 설계 제작되었다. 코일의 직경 및 권선 조건, 포머의 재질 및 구조, 차폐조건 등 안정된 전기용량 측정을 위한 설계 요구 조건을 컴퓨터 시뮬레이션과 실험적인 방법에 의해서 찾아내었다. 제작된 여러 개의 센서를 이용하여 동일한 조건의 사용오일 특성을 분석한 결과 0.25% 이내에서 일치하였다. 차량에 직접 장착하여 장기간 측정한 결과, 심한 진동과 온도 및 습도변화와 전자기적 잡음 등 열악한 차량의 조건에서도 매우 우수한 측정결과를 나타내었다.

• 한국지진공학회논문집
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• 제10권5호
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• pp.1-9
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• 2006

본 논문에서는 탄소섬유관으로 구속된 무근 콘크리트 원형 및 각형 기둥에 대한 축하중 및 횡하중 재하 실험을 수행하고, 실험결과를 바탕으로 하여 몬테카를로 해석을 이용한 신뢰성 해석을 수행함으로써 탄소섬유관으로 구속된 무근 콘크리트 원형 및 각형 기둥과 탄소섬유관으로 구속된 철근 콘크리트 원형 및 각형 기둥의 두 가지 경우에 대한 강도저감계수를 예측하였다. 해석 결과, 무근의 경우에는 강도저감계수가 0.7로 예측되었고, 철근이 삽입된 경우에는 강도저감계수가 0.85로 예측 되었다. 이러한 계수값은 원형과 각형인 경우 모두 같은 계수값을 보여주었다.

• 조명전기설비학회논문지
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• 제18권4호
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• pp.83-87
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• 2004

본 논문에서는 Magnetic Levitation Model 시스템을 이용하여 선형 액추에이터의 기본모델을 제안하고 전원 공급부의 입력 주파수의 변화로부터 액추에이터에 나타나는 현상을 Matlab프로그램을 활용하여 간접적 방법으로 고찰하였다. 그 결과는 실제적인 설계에 적용할 경우 설계 프로그램의 자료나 부분적 변경 시 참조 할 수 있으리라 사료된다. 본 논문에서 제안한 에너지 변환을 고려한Linear Actuator M3d진 시스템의 출력은 입력 주파수의 변화로부터 액추에이터가 고주파보다는 저주파에서 권선부에 나타나는 파형의 응답이 기준 입력파형에 더 근접함을 알 수 있었다. 이 결과를 바탕으로 Linear Actuator Model 시스템의 동작 시 특성이 실제 시스템에 활용할 때 간접적 방법으로 상당히 유용함을 확인 할 수 있었다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.47-50
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• 2005

In this paper, we investigate a filtering technique to reduce the adverse effect of long motor leads on H-bridge cascaded 7-level inverter fed ac motor drive. The switching surge voltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. However, the effect of switching surge appears un seriousin high voltage induction motor than low voltage induction motor. Consequently, we demonstrated that the filter connected to the motor terminals greatly reduces the transient voltage stress and ringing, moreover we show lowers the dv/dt of the inverter switching pulse. The results of simulation show the suppression of dv/dt and the reduced peak voltage at the motor end of a long cable.

• 전력전자학회논문지
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• 제20권2호
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• pp.160-166
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• 2015

This study proposes an improved cell balancing circuit for fast equalization among lithium-ion (Li-ion) batteries. A simple voltage sensorless charge balancing circuit has been proposed in the past. This cell balancing circuit automatically transfers energy from high-to low-voltage battery cells. However, the circuit requires a switch with low on-resistance because the balancing speed is limited by the on-resistance of the switch. Balancing speed decreases as the voltage difference among the battery cells decrease. In this study, the balancing speed of the cell balancing circuit is enhanced by using the auxiliary circuit, which boosts the balancing current. The charging current is determined by the nominal battery cell voltage and thus, the balancing speed is almost constant despite the very small voltage differences among the batteries. Simulation results are provided to verify the validity of the proposed cell balancing circuit.

• 전력전자학회논문지
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• 제12권6호
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• pp.472-482
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• 2007

본 논문에서는 PDP TV 전원에 적용된 LLT 변압기를 사용한 LLC 직렬공진 컨버터의 설계과정과 실험결과에 대해 서술하였다. 인덕터와 변압기를 하나의 변압기로 사용한 LLT 변압기는 전선방법과 코어의 공극에 따라 1, 2 차측 누설인덕턴스가 함께 증가한다. 이러한 LLT 변압기의 증가된 1, 2차측 누설인덕턴스는 LLC 직렬공진컨버터의 DC 전압이득에 영향을 준다. 따라서 본 논문에서는 LLT 변압기 적용 LLC 직렬 공진 컨버터의 전압이득 특성과 실험 결과에 대해 Math-CAD 시뮬레이션을 기본으로 한 이론적인 해석 및 600W 시제품을 통해 증명하였다.

• Journal of Power Electronics
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• 제14권6호
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• pp.1197-1207
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• 2014

Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권1호
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• pp.43-49
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• 2005

The high rate of voltage rise (dv/dt) in motor terminals caused by high-frequency switching and impedance mismatches between inverter and motor are known as the primary causes of irregular voltage distributions and insulation breakdowns on stator windings in IGBT PWM inverter-driven induction motors. In this paper, voltage distributions in the stator windings of an induction motor driven by an IGBT PWM inverter are studied. To analyze the irregular voltages of stator windings, high frequency parameters are derived from the finite element (FE) analysis of stator slots. An equivalent circuit composed of distributed capacitances, inductance, and resistance is derived from these parameters. This equivalent circuit is then used for simulation in order to predict the voltage distributions among the turns and coils. The effects of various rising times in motor terminal voltages and cable lengths on the stator voltage distribution are also presented. For a comparison with simulations, an induction motor with taps in the stator turns was made and driven by a variable-rising time switching surge generator. The test results are shown.