• 한국초전도ㆍ저온공학회논문지
• /
• 제9권4호
• /
• pp.32-36
• /
• 2007

We fabricated and tested a novel hybrid superconducting fault current limiter (SFCL) of three-phase $24kV_{rms}/630A_{rms}$ rating. In order to apply conventional resistive SFCLs into electric power systems, the urgent issues to be settled are as follows, such as initial installation price of SFCL, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. The ac loss and high cost of superconductor and cryostat system are main bottlenecks for real application. Furthermore in order to increase voltage and current ratings of SFCL, a lot of superconductor components should be connected in series and parallel which resulted in extreme high cost. In addition, the method to quench all components at the same instant needs very sophisticated skill and careful operation. Due to these problems, the practical applications of SFCL were pending. Therefore, in order to make practical SFCL, the price of SFCL should be lowered and should meet the demand of utilities. We designed novel hybrid SFCL which combines superconductor and conventional electric equipment including vacuum interrupter, power fuse and current limiting reactor. The main purpose of hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of superconductor and high fast switch. Consequently, it was possible to get the satisfactory test results using this method, and further works for field tests are in the process.

• 조명전기설비학회논문지
• /
• 제12권1호
• /
• pp.35-44
• /
• 1998

본 연구에서는 전류스트레스 및 필터소자의 용량저감을 고려한 다이오드 정류기의 입력LC필터 설계법을 기술하였다. 입력교류전류의 제3고조파 성분에 대하여 무한한 임피던스를 갖도록 LC병렬 공진회로와 출력측 직류콘덴서로 구성된 새로운 필터를 단위법(Per Unit)에 의해 설계하였다. 제안된 LC필터를 다이오드정류기에 적용하여 정상상태에서 실험한 결과, 입력교류전류의 제3고조파성분을 8.8〔%〕로 감소시켰으며, 입력역률은 종전의 표준형의 입력역률이 0.76인데 비하여 0.913으로 개선시켰다. 또한 필터소지자의 전압.전류용량감소와 함께, 설계된 입력LC필터는 다이오드 정류기계통에 악영향을 미치지 않았으며, 따라서 종래의 표준형 LC필터에 의한 방법과 비교하여 제안된 방법이 83.5〔%〕의 저용량의 필터로도 고역률의 정류가 가능함을 입증하였다.

• 한국인터넷방송통신학회논문지
• /
• 제21권3호
• /
• pp.35-42
• /
• 2021

초고주파 대역에서 TWTA(Traveling Wave Tube Amplifier)를 대체하기 위한 증폭기 연구가 활발히 이루어지고 있다. 반도체형 소자를 결합하여 높은 출력을 얻는 SSPA(Solid State Power Amplifier)의 경우 상대적으로 낮은 단일 소자의 출력으로 요구 출력을 충족하기 위해서는 저손실, 고효율의 결합 기술이 필요하다. 본 논문을 통해 8-way 도파관 결합기를 설계, 제작하여 20dB 이상의 반사 손실과 85% 이상의 결합 효율을 확인하였다. 전계 분석을 통해 결합기 내부의 임계 전력을 계산하여 안정적인 Power Rating을 확보하였고 전력 모니터링을 위한 커플러를 내장하여 소형화 및 경량화를 이루었다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 B
• /
• pp.1304-1306
• /
• 1996

A regenerative signal amplifying gate driver of self-excited electronic ballast is presented. It can be used for high pressure sodium (HPS) lamp without auxiliary external ignitor. Since the HPS lamp requires very high ignition voltage at start up, the resonant frequency of the circuit must be increased to obtain high voltage oscillations in spite of relatively small resonant current. The presented gate driver amplifies the current of gate drive transformer and raises the gate-source voltage Quickly to turn on the MOSFET switches. Hence, the resonant frequency can be increased more than 100kHz. The HPS lamp used in the simulation and experiment has the rating of 400W input power at 220V input ac voltage source. The experiments show that the resonant frequency is above 150kHz at start up.

• 조명전기설비학회논문지
• /
• 제12권3호
• /
• pp.114-123
• /
• 1998

The multi-resonant converter(MRC) minimizes a parasitic oscillation by using the resonant tank circuit absorbed parasitic reactances existing in a converter circuit. So it si possible that the converter operated at a high frequency has a high efficiency because the losses are reduced. Such a MHz high frequency applications provide a high power density [W/inch3] of the converter. But the resonant voltage stress across a switch of the resonant tank circuit is 4~5 times a input voltage. This h호 voltage stress increases the conduction loss because of on-resistance of a MOSFET with higher rating. Thus, in this paper we proposed the alternated multi-resonant converter (AT MRC) differ from the clamp mode multi-resonant converter and applicated it to the forward MRC. The AT forward MRC can reduce the voltage stress to 2~3 times a input voltage by using two series input capacitor. The control circuit is simple because tow resonant switches are driven directly by the output pulse of the voltage controled oscillator. This circuit type is verified through the experimental converter with 48V input voltage, 5V/50W output voltage/power and PSpice simulation. the measured maximum voltage stress is 170V of 2.9 times the input voltage and the maximum efficiency of 81.66% is measured.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2019년도 추계학술대회
• /
• pp.96-97
• /
• 2019

Pulse Width Modulation (PWM) is a widely adopted technique to drive the motor using the voltage source inverters. Since they generate high frequency Common Mode (CM) Voltage, a high shaft voltage in induction motor is induced which leads to parasitic capacitive currents causing adverse effects such as premature deterioration of ball bearings and high levels of electromagnetic emissions. This paper presents an Active Cancellation Circuit (ACC) which can significantly reduce the CM voltage hence the common mode current in the three phase induction motor drives. In the proposed method the CM voltage is detected by the capacitors and applied to the frame of the motor to cancel the CM voltage hence the CM current. Unlike the conventional methods the proposed method does not insert the transformer in between the inverter and motor, a high power rating three phase transformer is not required and no losses associated with it. In addition the proposed method is applicable to any kind of PWM motor drives regardless of their PWM methods. The effectiveness of the proposed method is proved by the experiments with a three phase induction motor (1.1kW 415V/60Hz) combined with a three phase voltage source inverter modulated by the Space Vector Modulation (SVM).

• 전력전자학회논문지
• /
• 제4권5호
• /
• pp.449-454
• /
• 1999

본 논문에서는 자동차 헤드라이트용 고압방전등 안정기의 새로운 전력변환 구조를 제안한다. 제안된 전력변환 구조는 기존의 안정기와 같이 고압방전등의 전력제어를 하는 고주파 DC-DC 컨버터와 저주파 DC-AC 인버터로 구성되어 있지만, 컨버터에 보조권선을 사용하여 고압방전등의 점등개시용 절연파괴전압을 얻기 위한 고압변압기의 1차측 전압을 DC-DC 컨버터의 직류단과 분리하여 공급하게 되어 있다. 따라서 기존의 시스템에 비해 작은 전압 정격을 가지는 소자를 사용할 수 있어 시스템의 효율 향상 및 가격 절감을 할 수 있다.

• 전력전자학회논문지
• /
• 제14권3호
• /
• pp.235-242
• /
• 2009

본 논문에서는 새로운 비대칭 PWM 제어 방식의 양방향 하프브리지 컨버터를 제안한다. 제안한 컨버터는 구조가 간단하고 넓은 듀티 범위를 가지므로 연료전지와 같은 넓은 전압변동을 가지는 응용에 적합하다. 제안한 비대칭 PWM 방식은 기존의 위상각제어 방식에 비해 스위치 및 변압기의 동작전류를 큰 폭으로 낮추었고 ZVZCS와 동기 정류 방식을 적용하여 높은 효율과 전력밀도를 가질 수 있다. 기존 컨버터와의 비교 분석을 수행하였으며 실험을 통해 본 방식의 타당성을 검증하였다.

• Journal of Electrical Engineering and Technology
• /
• 제2권1호
• /
• pp.55-60
• /
• 2007

This paper proposes a hydraulic pump system that uses a variable speed SR drive and constant capacity pump. For the design of the SRM (Switched Reluctance Motor) and digital controller, base speed and rating torque are determined from the mechanical specifications of the hydraulic pump. In order to minimize the power consumption during the maintaining of preset oil-pressure, the pressure control system changes the maximum oil-pressure band and flow rate according to the motor speed. The DSP control system adjusts the oil-pressure and the speed of the SRM from the pressure sensor signal, due to conservation of power consumption by the hydraulic pump. A 2.2Kw, 12/8 pole SR motor and DSP based digital controller are designed and tested with experimental set-up. The test results indicate that the system has some good features such as high efficiency and rapid response characteristics.

• 전력전자학회논문지
• /
• 제18권4호
• /
• pp.312-321
• /
• 2013

In this paper, high efficiency control method for flyback inverter with synchronous rectifier(SR) based on photovoltaic AC modules is proposed. In this control method, the operation of SR is classified according to the voltage spike across main switch SP. When the voltage spike across SP is lower than the rating voltage of SP, the operation of active clamp circuit is interrupted for reducing the switching loss of auxiliary switch. In this time, the SR is operated for soft-switching of SP. When the voltage spike across Sp is higher than the rating voltage of SP, the operation of active circuit is activated for reducing the voltage spike. The SR is operated for reducing the conduction loss of secondary output diode. Thus, a switching loss of the main switch can be reduced in low power region, and weighted-efficiency can be improved. A theoretical analysis and the design principle of the proposed method are provided. And validity is confirmed through simulation and experimental results.