• 조명전기설비학회논문지
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• 제14권1호
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• pp.82-88
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• 2000

본 논문은 궤환 권션을 갖는 $S^4-PFC$ 컨버터에서 기존의 DC 버스 전압 제한 능력과 높은 효율을 유지하면서 입력 전류 파형을 개선시킬 수 있는 저비용의 보조회로펀 제안하였다. 제안한 컨버터를 검증하지 위하여 궤환 권선을 갖는 컨버터를 분석하였다. 제안한 컨버터의 성능응 입증하기 위해 상용 라인 입력 전압범위에서 5[V], 65[W] 출력과 스위칭 주파수 100[kHz]에서 동작하는 컨버터 설계하였다. 그리고 실험을 통하여 기존 컨버터에 비하여 라인 전류 파형의 첨두값이 50[%] 감소하고 라인 주기에서 전력이용률이 증가하였다.

• 한국수소및신에너지학회논문집
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• 제31권3호
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• pp.307-313
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• 2020

The 3.9 liter diesel engine with a mechanical fuel injection system was converted to di-methyl ether (DME) engine and performance optimized. In order to switch to the DME engine, the plunger of the high pressure fuel pump was replaced and the diameter of the injector nozzle was increased. Through this, the disadvantage of DME having low calorific value per volume can be compensated. To optimize the performance, the number of injector nozzle holes, injector opening pressure, and fuel injection timing were changed. As a result, the optimum number of injector nozzle holes was 5, the injector opening pressure was from 15 MPa to 18 MPa, and the injection timing was 15 crank angle degree before top dead center (CAD BTDC). The power was at the same level as the base diesel engine and nitrogen oxides (NOx) emissions could be reduced.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.265-267
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• 2008

As generally recognized, the driving performance of a SRM at higher speed will be degraded due to the effects of back electromagnetic force (EMF). This phenomenon can be improved via voltage boosting. So in this paper an improved converter of enhancing the performance for four-phase switched reluctance motor (SRM) is proposed. By using one additional capacitor and switches, an extra controllable boosted voltage can be produced during the rise and fall periods of a motor phase current. Then this active boosted voltage can reduce the effect of EMF on the current, particularly at high speeds. The attractive features of the proposed converter are as follows: obtaining boosted voltage to improve performance of SRM with same numbers of switch and diode as asymmetric converter, having higher control flexibility and capability of boosting voltage compared with passive boosting converters, possessing lower cost and simple control in comparison with existing active boosting converters. The performances of the proposed circuit are verified by the simulation and experiment results.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.28-31
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• 2005

To verify the feasibility of bifilar winding type superconducting fault current limiter (SFCL) using BSCCO tape, two types of magnets were fabricated and tested by short-circuit in this research. Even if the FCL using high Tc superconducting (HTS) tape has zero resistance in normal state, it needs to be wound as a bifilar winding for zero inductance. Solenoid type and pancake type bifilar winding magnets are designed and fabricated with the same length of BSCCO tape. The test system consists of AC power supply, transformer, fault switch, load and bifilar winding magnet. The applied AC voltages during fault duration, 0.1s, were from 0.5V to 20V. The test results without bifilar winding magnet were compared with those with each type magnets. The test results include voltage against magnet, transport current and generated resistance curve. Thermal stability, the recovery time, was studied from the results of two type magnets. The pancake type was the most effective to limit fault current but the solenoid type was thermally the most stable. From this research, short-circuit characteristics of the two types were obtained.

• ETRI Journal
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• 제29권4호
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• pp.421-429
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• 2007

This paper presents a direct-conversion CMOS transceiver for fully digital DS-UWB systems. The transceiver includes all of the radio building blocks, such as a T/R switch, a low noise amplifier, an I/Q demodulator, a low pass filter, a variable gain amplifier as a receiver, the same receiver blocks as a transmitter including a phase-locked loop (PLL), and a voltage controlled oscillator (VCO). A single-ended-to-differential converter is implemented in the down-conversion mixer and a differential-to-single-ended converter is implemented in the driver amplifier stage. The chip is fabricated on a 9.0 $mm^2$ die using standard 0.18 ${\mu}m$ CMOS technology and a 64-pin MicroLead Frame package. Experimental results show the total current consumption is 143 mA including the PLL and VCO. The chip has a 3.5 dB receiver gain flatness at the 660 MHz bandwidth. These results indicate that the architecture and circuits are adaptable to the implementation of a wideband, low-power, and high-speed wireless personal area network.

• 전자공학회논문지S
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• 제36S권8호
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• pp.113-122
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• 1999

본 논문에서는 스위칭 손실을 저감시키고, 높은 주파수 동작에 적합한 새로운 Watkins - Johnson 공진형 컨버터를 제안하였다. 정상상태 해석에서는 제안 된 공진형 컨버터의 전압이득은 스위칭 주파수에 의존하게 된다는 것을 밝혔다. 따라서 컨버터의 출력전압을 안정시키기 위해서는 부하 전류 변화에 따라 스위칭 주파수도 함께 변화시켜야한다. 또한 해석결과를 토대로, 스위치의 전압 스트레스를 최소화시키고, 영전압 스위칭되는 조건하에서 컨버터의 공진소자 값을 결정할 수 있는 최적의 설계방식을 제시하였다. 끝으로 Watkins-Johnson 공진형 컨버터의 실험회로를 구성하여 최적 설계방식의 타당성을 입증하였다.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1310-1315
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• 2003

GIS(Gas Insulated Switchgear) is power equipment with excellent dielectric strength and is economy merit in high confidence and stability. But, because of structural characteristics, this is difficult to monitor externally and provide much loss in the event of an accident. Recently, because equipment of GIS is occurring problem of confidence used for a long time, development of diagnosis technique have been importantly recognized. therefore, measurement and analysis of PD much has been generally used for equipment of GIS. But, in case of measurement of PD at field, real trouble signals is difficult to classify noise. Accordingly, a variety of trouble conditions for DS are simulated, and detected signals are analyzed by the application of electrical and mechanical methods. For this analysis, detected signals are accumulated according to phase-magnitude with the application of induction sensor, and then we analyzed the characteristics. For the simulation experiment, we make DS for 170KV GIS and analyze the characteristics of detected signals with the application of neural network algorithm. last, we have measured DS for GIS at field, and then have analyzed detected signals.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.838-848
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• 2018

This paper proposes a single-phase buck-boost AC-AC converter. It consists of three legs with six switching units (each unit is composed of an active switch and a diode) and its input and output ports share a common ground. It can provide buck-boost voltage operation and immune from shoot-through problem. Since only two switching units are involved in the current paths, the conduction losses are low, which improves the system efficiency. The operation principle of the proposed circuit is firstly presented, and then, various operation conditions are introduced to achieve different output voltages with step-changed frequencies. Additionally, the parameters design and comparative analysis of the power losses are also given. Finally, experimental results verify the correctness of the proposed converter.

• 전기학회논문지
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• 제65권5호
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• pp.785-793
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• 2016

This paper analyzes an LCL-type isolated dc-dc converter operating for constant output voltage in the continuous conduction mode(CCM) with resistances of parasitic losses-static drain-source on resistance of power switch, ESR of resonant network(L-C-L)-using a high loaded quality factor Q assumptions and fourier series techniques. Simple analytical expressions for performance characteristics are derived under steady-state conditions for designing and understanding the behavior of the proposed converter. The voltage-driven rectifier is analyzed, taking into account the diode threshold voltage and the diode forward resistance. Experimental results measured for a proposed converter at low input voltage and various load resistances show agreement to the theoretical performance predicted by the analysis within maximum 4% error. Especially in the case of low output voltages and large loads, It is been observed that introduction of both rectifier and the parasitic components of converter had considerable effect on the performance.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권1호
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• pp.54-61
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• 2000

Conventionally, ZVS FB DC/DC converter was controlled by monolithic IC UC3879, which includes the functions of oscillator, error amplifier and phase-shift circuit. Also, microprocessor and DSP have been widely used for the remote control and for the immediate waveform control in ZVS FB DC/DC converter. However the conventional microprocessor controller is complex and difficult to control because the controller consists of analog and digital parts. In the case of the control of FB DC/DC converter, the output is required of driving a direct signal to the switch drive circuits by the digital controller. So, this paper presents the method and realization of designing the digital-to-phase shift PWM circuit controlled by DSP (TMX320C32) in a 2,500A, 40㎾ ZVS FB DC/DC converter.