• Advances in aircraft and spacecraft science
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• 제7권5호
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• pp.425-440
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• 2020

The work presented herein is a numerical investigation of the flow field inside a resonant igniter, with the aim of predicting the performances in terms of cavity temperature and noise spectrum. A resonance ignition system represens an attractive solution for the ignition of liquid rocket engines in space missions which require multiple engine re-ignitions, like for example debris removal. Furthermore, the current trend in avoiding toxic propellants leads to the adoption of green propellant which does not show hypergolic properties and so the presence of a reliable ignition system becomes fundamental. Resonant igniters are attractive for in-space thrusters due to the low weight and the absence of an electric power source. However, their performances are strongly influenced by several geometrical and environmental parameters. This motivates the study proposed in this work in which the flow field inside a resonant igniter is numerically investigated. The unsteady compressible Reynolds Averaged Navier-Stokes equations are solved by means of a finite volume scheme and the effects of several wall boundary conditions are investigated (adiabatic, isothermal, radiating). The results are compared with some available experimental data in terms of cavity temperature and noise spectrum.

• 전기학회논문지
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• 제59권4호
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• pp.768-773
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• 2010

In this paper, we study on an optimal design of a triple-band PIFA (Planar Inverted-F Antenna) of 433 MHz, 912 MHz and 2.45 GHz by using evolution strategy. Generally, the resonant frequency of the PIFA is determined by the width and length of a U-type slot used. However the resonant frequencies of the multiple U slots are varied by the mutual effect of the slots. Thus the optimal width and length of U-type slots are determined by using an optimal design program based on the evolution strategy. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is constructed for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The resonant frequencies of initial model are 439.5 MHz, 981.5 MHz and 2.563 GHz. However, the resonant frequencies of the triple-band PIFA yielded by the optimal design program are 430.5 MHz, 907 MHz and 2.4515 GHz. Measured resonant frequencies are 433.5 MHz, 905.5 MHz and 2.454GHz, which show a good agreement with the simulation results.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.842-848
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• 2011

The current study proposes the design of a hybrid series-parallel resonant converter (SPRC) and a three-stage Cockcroft-Walton voltage multiplier for precisely adjusting the power generated by a continuous wave (CW) $CO_2$ laser. The design of a hybrid SPRC, called LCC resonant converter, is described, and the fundamental approximation of a high-voltage and high-frequency (HVHF) transformer with a resonant tank is discussed. The results of the current study show that the voltage drop and ripple of a three-stage Cockcroft-Walton voltage multiplier depend on frequency. The power generated by a CW $CO_2$ laser can be precisely adjusted by a variable-frequency controller using a DSP (TMS320F2812) microprocessor. The proposed LCC converter could be used to obtain a maximum laser output power of 23 W. Moreover, it could precisely adjust the laser output power within 4.3 to 23 W at an operating frequency range of 187.5 to 370 kHz. The maximum efficiency of the $CO_2$ laser system is approximately 16.5%, and the minimum ripple of output voltage is about 1.62%.

• 전력전자학회논문지
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• 제4권1호
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• pp.91-98
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• 1999

본 논문에서는 역률개선용 단일 스위치 부스트 플라이백 결합형 ZCS quasi-resonant converter(QRC)를 제안한다. 제안된 컨버터는 입력전류를 불연속 모드로 동작시켜 역률을 개선하며 입력전류의 zero-crossing-point에서의 왜곡을 개선함으로써 고조파를 감소시켜 역률을 향상시켰으며 좋은 출력전압의 regulation 성능을 가지고 있다. 그리고 체계적인 설계를 위하여 설계식을 제안하였으며 제안된 설계식을 통하여 프로토타입 컨버터를 설계하였다. 실험결과 효율은 약 86%, 역률은 약 0.985이상을 얻었다. 따라서 본 컨버터는 스위칭 주파수가 수백 kHz이상이고 높은 regulation성능을 요구하는 낮은 전압의 소용량 컨버터에 적합하다.

• 조명전기설비학회논문지
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• 제17권6호
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• pp.113-118
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• 2003

비선형 부하는 고조파 발생원으로 고조파 전압원과 고조파 전류원의 두종류로 분류된다. 직렬동조필터는 개인용 컴퓨터 부하와 같이 직류 캐패시터가 있는 비선형 부하로 고조파 전압원에 매우 효과적으로 고조파를 저감시킨다. 병렬동조필터는 교류 구동장치와 같이 직류 리액터가 있는 비선형 부하로 고조파 전류원에 적합하다. 본 논문에서는 직렬 및 병렬 동조 필터의 고조파 저감 특성과 비교를 검토하고 실험하였다. 국제 고조파 관리 기준인 IEC 1000-3-2 으로 직렬 및 병렬 동조필터의 고조파 저감 효과를 평가하고자 한다.

• Journal of Power Electronics
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• 제16권4호
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• pp.1483-1493
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• 2016

Multiple parallel inverters have multiple resonant frequencies that are influenced by many factors. This often results in stability and power quality problems. This paper develops a multiple input multiple output model of grid-connected inverter systems using a closed-loop transfer function. The influence factors of the resonant characteristics are analyzed with the developed model. The analysis results show that the resonant frequency is closely related to the number, type and composition ratio of the parallel inverters. To suppress resonance, a scheme based on virtual impedance is presented, where the virtual impedance is emulated in the vicinity of the resonance frequency. The proposed scheme needs one inverter with virtual impedance control, which reduces the design complexity of the other inverter controllers. Simulation and experimental tests are carried out on two single phase converter-based setups. The results validate the correctness of the model, the analytical results and the resonant suppressing scheme.

• 전기학회논문지
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• 제64권6호
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• pp.885-890
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• 2015

LLC resonant converter has been widely used because of its high efficiency and high energy density. In this paper, we designed a LLC resonant converter as the main power supply of the Nd:YAG pulse laser. First harmonic approximation (FHA) is used to model the LLC resonant converter. FHA equivalent circuit model and the transfer function of the LLC resonant converter is proposed. Soft start technology is also used to suppress the surge current. The laser output simulation test result is identical with the practical test, the laser energy of every pulse can reach up to 2.5J, and the pulse per second (PPS) can be adjusted from 6 to 18. The power system is verified stable and reliable by both of the simulation and experiment results.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.383-392
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• 2016

This paper proposes the design considerations of resonant network and transformer magnetics for 500 kHz high switching frequency LLC resonant converter. The high power density can be effectively achieved by adopting high switching frequency which allows small size passive components in the converter. The design methodology of magnetizing inductance is derived for zero voltage switching (ZVS) condition, and the design methodology of the transformer and output capacitance is derived to achieve high power density at high operating frequency. Moreover, the structure of transformer is analyzed to obtain the proper inductance value for high switching operation. To verify the proposed design methodology, simulation and experimental results will be presented including temperature of passive and active components, and power conversion efficiency to evaluate dominant power loss. In addition, the validity of magnetics design will be evaluated with operating waveforms of the prototype converter.

• 전기학회논문지
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• 제62권8호
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• pp.1101-1107
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• 2013

A light emitting diodes(LED) lighting has been increasingly used due to its low power consumption, long life time, high efficiency, and environment friendly characteristics. Also various power converters has been applied to drive these LED lighting. Among many power converters, a LLC resonant converter could be applied for LED lighting because of its high efficiency and high power density. Furthermore, the function of power factor correction(PFC) might be added. In this paper, 1-stage asymmetrical LLC resonant converter is proposed. The proposed converter performs both input-current harmonics reduction and PFC using the discontinuous conduction mode(DCM). The proposed 1-stage LLC resonant converter approach has the lower voltage stress across switching devices and achieve the zero voltage switching(ZVS) in switching devices. To verify the performance of the proposed converter, simulation and experimental results from a 300[W] prototype are provided.

• 조명전기설비학회논문지
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• 제19권7호
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• pp.107-112
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• 2005

본 논문은 직렬공진 인버터를 이용한 고전압 커패시터 충전형 전원장치(CCPS)에 관하여 기술하였다. 본 논문에서 사용된 고전압 CCPS는 PLL제어를 사용한 45[Khz]의 직렬공진 인버터를 사용하여 고효율제어를 하였으며, 고전압 변압기를 사용하였다. CCPS의 성능을 평가하기 위하여 14[nF]의 부하에 100[kV]의 출력전압을 300[Hz]의 방전주기를 가지고 실험하였다. 실험결과 최대출력은 18.75[kJ/sec]이고, 방전시간은 200[Hz]로 운전하였으며, 충전시간은 4.5[mS]임을 확인하였다.