• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2795-2797
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• 1999

Several power factor correction(PFC) circuits are presented to achieve high PF electronic ballast for both voltage-fed and current-fed electronic ballast. The proposed PFC circuits use valley-fill(VF) type DC-link stages modified from the conventional VF circuit to adopt the charge pumping method for PFC operations during the valley intervals. In voltage-fed ballast, charge pump capacitors are connected with the resonant capacitors. In current-fed type, the charge pump capacitors are connected with the additional secondary-side of the power transformer. The measured PF and THD are higher than 0.99 and 15% for all proposed PFC circuits. The lamp current CF is also acceptable in the proposed circuits. The proposed circuit is suitable for implementing cost-effective electronic ballast.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.266-269
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• 1999

Several power factor correction(PFC) circuits are presented to achieve high PF electronic ballast for both voltage-fed and current-fed electronic ballast. The proposed PFC circuits use valley-fill(VF) type DC-link stages modified from the conventional VF circuit to adopt the charge pumping method for PFC operations during the valley intervals. In voltage-fed ballast, charge pump capacitors are connected with the resonant capacitors. In current-fed type, the charge pump capacitors are connected with the additional secondary-side of the power transformer. The measured PF and THD are higher than 0.99 and 15% for all proposed PFC circuits. The lamp current CF is also acceptable in the proposed circuits. The proposed circuit is suitable for implementing cost-effective electronic ballast.

• 전력전자학회논문지
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• 제4권6호
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• pp.515-522
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• 1999

형광등용 전자식 안정기의 개발에 있어서, 최근 선전류 고조파 성분의 제한에 관한 여러 가지 규제를 만족시키기 위해 역률 개선 회로를 부가하는 것이 권장되고 있다. 일반적으로는 부스트 컨버터를 가장 많이 사용하고 있지만 전체 제품의 가격 상승 및 EMI 발생 등의 단점 때문에 설계에 있어서 상당한 제약을 받게 된다. 본 논문에서는 역률 개선을 수동소자로만 이용하여 전압원 및 전류원 방식의 공진형 인버터를 채택하는 형광등용 전자식 안정기를 저가격화, 고역률화하는 것을 목적으로 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.260-265
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• 2001

This paper describes total flow control of an ice slurry system for pump energy saving. Similar turbo machinery has a characteristic that input power ratio is proportional to the three time of revolution speed ratio. To reduce the energy cost of brine pump in ice slurry storage systems, inverter is adapted instead of 3-way valve to control the speed of brine pump motor. One type of cooling load profile was used as driving load of the system, generated by a boiler and warm water storage tank. As results of the laboratory test, energy consumption and cost of the pump were reduced by 11.4%.

• 한국추진공학회지
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• 제9권3호
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• pp.25-37
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• 2005

터보펌프 공급방식 발사체 추진기관은 공급 시작 시점에서부터 종료되는 시점까지 산화제 터보펌프 입구에서의 온도 요구조건을 충족시켜야 한다. 이러한 조건이 만족되지 못할 경우 터보펌프 입구에서 캐비테이션이 발생하여 펌핑(pumping) 성능이 저하되고, 심한 경우 펌프의 손상을 초래할 수 있다. 따라서 극저온 액체산소를 사용하는 액체로켓 추진기관에서는 액체산소의 온도 상승에 대한 적확한 예측이 필수적이다 본 논문에서는 탱크 내의 액체산소 온도상승과 관계된 탱크 내 해석 방법을 체계적으로 제시하였고, 부력동기 경계층 이론을 적용하여 터보펌프 공급방식 로켓 추진기관의 충전, 대기, 선가압, 비행 등의 전 과정을 통하여 탱크에 충전된 액체산소의 온도상승을 예측할 수 있는 모델을 제시 하였다.

• 한국추진공학회지
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• 제8권3호
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• pp.27-36
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• 2004

본 논문에서는 AMESim을 이용하여 터보펌프 모사 장치 중 압력조절계에 대한 시뮬레이션을 수행하였다. 시스템의 최적화를 통하여 압력조절계의 과도 및 정상상태의 특성과 응답성을 확인하였다. 연구결과들은 향후 제어밸브의 성능 검증 및 제어로직 검증을 위한 추력제어시스템 성능 시험장치 및 엔진공급계 인증시험설비의 설계와 운용 시 적극 반영할 계획이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.227-230
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• 2001

This paper deals with a bidirectional ac-dc converter used in ups system application. We propose a Voltage-Source-Charge-Pump-Power-Factor-Correction(VS-CPPFC) ac-dc converters. First of all, we propose a charge pump power-factor-correction converter. Secondly, we derive and analyse a unity power factor condition. The proposed topology is based on a half-bridge for the primary and a current-fed push pull for the secondary side of a high frequency isolation transformer. The advantage of bidirectional flow of power achieved by using the same power components is that the circuit is simple and efficient. And the galvanically isolated topology is specially attractive in battery charge/discharge circuits in ups system. We design equivalent model for the steady-state circuit and analyse operation waveforms for each mode. We show that the proposed model can be applied to ups system by simulation processes.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.211-215
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• 2004

For design of cryogenic propellant feeding system, one of the main requirements is to meet temperature requirement for satisfying turbo-pump NPSH requirement. In this paper improved method of estimating the thermal stratification in liquid oxygen tank is presented to help design. In the case of liquid rocket using turbo-pump, the inner pressure of liquid oxygen tank is maintained low, so vaporization of liquid oxygen is generally occurred. In this paper, inner process of LOX tank is analyzed by two phase flow modeling. The vaporization rate and required helium mass is investigated.

• 전력전자학회논문지
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• 제27권5호
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• pp.425-430
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• 2022

A pumped storage power station is an important means to solve the problem of peak load regulation and ensures the safety of power grid operation. The doubly fed variable-speed pumped storage (DFVSPS) system adopts a doubly fed induction machine (DFIM) to replace the synchronous machine used in traditional pumped storage. The stator of DFIM is connected to the power grid, and the three-phase excitation windings are symmetrically distributed on the rotor. Excitation current is supplied by the converter. The active and reactive power of the unit can be quickly adjusted by adjusting the amplitude, frequency, and phase of the rotor-side voltage or current through the converter. Compared with a conventional pumped storage hydropower station (C-PSH), DFVSPS power stations have various operating modes and frequent start-up and shutdown. This study introduces the structure and principle of the DFVSPS unit. Mathematical models of the unit, including a model of DFIM, a model of the pump-turbine, and a model of the converter and its control, are established. Fast power control strategies are proposed for the unit model. A 300 MW model of the DFVSPS unit is established in MATLAB/Simulink, and the response characteristics in generating mode are examined.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.777-785
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• 2015

In agricultural systems, significant amount of energy is consumed during irrigation periods. Therefore operating irrigation systems with electrical energy produced by solar energy is very important. It is be possible to operate irrigation systems which have small-pump power like drip-irrigation with electrical energy produced by solar energy. Electrical energy produced by photovoltaic panels can vary from the estimated value due to environmental factors. Consequently analysis of a real system's performance is important. Thus, more correct projections can be made for the systems which will be designed. In this study, induction motor-pump mechanism for drip-irrigation system is operated with photovoltaic generator. Solar energy capacity of the established system is evaluated by measurements in irrigation periods. By means of simulations, power values produced by system and gained from the actual system are compared. Additionally the performance of induction motor is analyzed with the help of the driver system that increases the efficiency and controls the motor. As regards of results, design values of the drip-irrigation systems fed with solar energy in Southeastern Anatolian Regions of Turkey are obtained. Performance results of induction motor controlled with driver are also provided.