• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 F
• /
• pp.2650-2652
• /
• 1999

To satisfy the demand for small size, light weight. high density power supply, the switching frequency of DC/DC converters has been increased. The PWM control of the conventional SMPS have a switching frequency that a level of the conducted noise spectra contribute to switching frequency band. So the electronic equipment is not only affected from that but is restricted to internal regulation like CISPR, FCC, and VDE. In this paper, we analyzed Bi-FM. Bi-FM is two fixed switching frequency with a modulation frequency. So emission spectrum of Bi-FM control signal is spreaded and spectral power level is reduced. In this paper, we analyze the spectral analysis of Bi-FM control signal and the spectral comparison between the PWM control and Bi-FM control. And we confirm that reduced the spectrum power level through simulation using Pspice and experiment.

• Journal of Electrical Engineering and Technology
• /
• 제12권3호
• /
• pp.1187-1194
• /
• 2017

In this paper, a high step-up DC-DC PWM converter with continuous input current and low voltage stress is presented for renewable energy application. The proposed converter is composed of a boost converter integrated with an auxiliary step-up circuit. The auxiliary circuit uses an additional coupled inductor and a balancing capacitor with voltage doubler and switching capacitor technique to achieve high step-up voltage gain with an appropriate switch duty cycle. The switched capacitors are charged in parallel and discharged in series by the coupled inductor, stacking on the output capacitor. In the proposed converter, the voltage stress on the main switch is clamped, so a low voltage switch with low ON resistance can be used to reduce the conduction loss which results in the efficiency improvement. A detailed discussion on the operating principle and steady-state analyses are presented in the paper. To justify the theoretical analysis, experimental results of a 200W 40/400V prototype is presented. In addition, the conducted electromagnetic emissions are measured which shows a good EMC performance.

• 조명전기설비학회논문지
• /
• 제22권5호
• /
• pp.47-52
• /
• 2008

본 논문에서는 모의 GIS 내부에 도전성 파티클, 미소돌기, 연면방전을 모의함으로 전하의 축적과 전계의 집중이 용이하도록 하여 부분방전을 모의하였다. 이때 부분방전 발생과 진전에 따른 방사전자파를 스펙트럼 분석기와 EMI EMC 측정용 안테나($30{\sim}2,000[MHz]$)를 사용하여 측정 분석하였다. 이러한 결과를 바탕으로 0.3[GHz]에서 1.7[GHz]대역에서 UHF법을 활용한 절연진단이 가능한 UHF 구형 센서를 설계하였다. 이러한 연구결과는 $SF_6$를 사용하는 실제 GIS 및 전력설비의 UHF 절연진단 시스템에 적용 가능한 UHF 진단센서로 활용할 수 있을 것이다.

• Journal of Power Electronics
• /
• 제17권6호
• /
• pp.1445-1453
• /
• 2017

In this study, a new zero-voltage transition (ZVT) buck converter with coupled inductor using a synchronous rectifier and a lossless clamp circuit is proposed. The regular buck converter with tapped inductor has extended duty cycle for high step-down applications. However, the leakage inductance of the coupled inductor produced considerable voltage spikes across the switch. A lossless clamp circuit is used in the proposed converter to overcome this problem. The freewheeling diode was replaced with a synchronous rectifier to reduce conduction losses in the proposed converter. ZVT conditions at turn-on and turn-off instants were provided for the main switch. The synchronous rectifier switch turned on under zero-voltage switching, and the auxiliary switch turn-on and turn-off were under zero-current condition. Experimental results of a 100 W-100 kHz prototype are provided to justify the validity of the theoretical analysis. Moreover, the conducted electromagnetic interference of the proposed converter is measured and compared with its hard-switching counterpart.

• Journal of Industrial and Engineering Chemistry
• /
• 제68권
• /
• pp.387-392
• /
• 2018

Various technical approaches and concepts have been proposed to develop conductive super-hydrophobic (SH) surfaces. However, most of these approaches are not usable in practical applications because of insufficient adhesion and cost issues. Additionally, durability and uniformity issues are still in need of improvement. The goal of this research is to produce a large-area conductive SH surface with improved adhesion performance and uniformity. To this end, carbon nanotubes (CNT) with a high aspect ratio and elastomeric polymer were utilized as a conductive filler and matrix, respectively, to form a coating layer. Additionally, nanoscale silica particles were utilized for stable implementation of the conductive SH surface. To improve the adhesion properties between the SH coating layer and substrate, pretreatment of the substrate was conducted by utilizing both wet and dry etching processes to create specific organic functional groups on the substrate. Following pretreatment of the surface, a zirco-aluminate coupling agent was utilized to enhance adhesion properties between the substrate and the SH coating layer. Raman spectroscopy revealed that adhesion was greatly improved by the formation of a chemical bond between the substrate and the SH coating layer at an optimal coupling agent concentration. The developed conductive SH coating attained a high electromagnetic interference (EMI) shielding effectiveness, which is advantageous in self-cleaning EMI shielding applications.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
• /
• pp.499-503
• /
• 2009

In this study, the dynamic characteristic of a contact wire and pantograph suppling electrical power to high-speed trains are investigated from an electrical response point of view. To analysis power line disturbance by induced contact loss phenomenon for high speed operation, a hardware Simulator which considered contact loss between contact wire and the pantograph as well as contact wire deviation is developed. It is confirmed that a contact wire and pantograph model are necessary for studying the dynamic behavior of the pantograph system. One of the most important needs accompanied by increasing the speed of high-speed train is reduced that an arc phenomenon by loss of contact brings out EMI. In case of a high-speed train using electrical power, as comparison with diesel rolling stock, PLD(Power Line Disturbance) such as harmonic, transient voltage and current, EMI, dummy signal injection etc usually occurs. Throughout experiment, it is verified that an arc phenomenon is brought out for simulator operation and consequently conducted noise is flowed in electric circuit by power line disturbance.

• 융합신호처리학회논문지
• /
• 제12권4호
• /
• pp.333-340
• /
• 2011

한국천문연구원은 한일상관센터 (Korea-Japan Correlation Center, KJCC)에 2009년부터 한일공동VLBI상관기(Korea-Japan Joint VLBI Correlator, KJJVC)를 설치하여 운영하고 있다. 한일공동VLBI상관기는 한국우주전파관측망(Korean VLBI Network, KVN), VERA(VLBI Exploration of Radio Astrometry), JVN(Japanese VLBI Network) 및 공동 관측망 등에서 관측한 VLBI(Very Long Baseline Interferometer) 데이터를 상관처리하고, 과학적 목적을 위해 관측데이터를 처리하는 전용 계산기로 사용된다. KJJVC는 각 구성시스템 사이의 데이터 입출력 규격으로 VLBI 국제표준인 VSI(VLBI Standard Interface)를 따르고 있다. 특히 관측된 데이터를 상관처리하기 위해 고속재생기인 Mark5B시스템과 동기재생처리장치(Raw VLBI Data Buffer, RVDB) 사이에는 1024 Mbps급으로 데이터가 전송된다. 고속 데이터 전송에 있어 발생하는 전자기 방해 (Electromagnetic Interference, EMI)는 관측데이터의 손실을 야기 시키며, 전송 케이블의 길이가 길수록 손실 발생빈도가 많고, 디지털 데이터 신호의 전압레벨을 감소시켜 데이터 인식 오류를 초래한다. 따라서 본 논문에서는 VSI 규격의 통신에서 발생하는 EMI 잡음 정도를 측정하고, 데이터 손실을 최소화할 수 있는 방법으로 1) RC 필터를 사용한 방법, 2) Microstrip 라인을 이용한 임피던스 매칭, 3) Differential line driver를 이용한 신호 복원 방법 등을 제안하였다. 각 제안방법들의 유효성을 확인하기 위해 제안방법들은 시뮬레이션과 실험적인 구현을 통하여 성능시험을 수행하였으며, 각각의 제안 방법이 VSI 규격의 고속 데이터 전송에 유효함을 확인하였다.

• 한국추진공학회지
• /
• 제18권3호
• /
• pp.70-77
• /
• 2014

본 논문은 한국형 2.75 인치 로켓 추진기관의 독자 모델 개발에 관하여 기술하였다. 개발된 한국형 2.75 인치 로켓 추진기관은 추진제 그레인의 형상변경을 통하여 화염안정성을 증대시켰으며, 점화장치에 EMI 필터를 장착하여 우발점화 방지기능을 추가하였다. 그리고 노즐 형상 변경 및 날개 수 증가를 통하여 비행안정성의 향상을 가질 수 있었다. 지상연소시험 및 온도충격시험을 통해 추진제의 성능을 검증하였으며, 약 210 발의 비행시험을 통해 기 배치된 추진기관과 비행성능이 동일함을 입증하였다. 성능개량과 더불어 한국형 독자모델 개발로 인한 지적재산권 문제 극복에 기여할 수 있는 근간을 마련했다는데 그 의의가 있다.

• Journal of Electrical Engineering and Technology
• /
• 제10권1호
• /
• pp.205-215
• /
• 2015

Common mode (CM) conducted interference are predicted and compared with experiments in a motor drive system of Electric vehicles in this study. The prediction model considers each part as an equivalent circuit model which is represented by lumped parameters and proposes the parameter extraction method. For the modeling of the inverter, a concentrated and equivalent method is used to process synthetically the CM interference source and the stray capacitance. For the parameter extraction in the power line model, a computation method that combines analytical method and finite element method is used. The modeling of the motor is based on measured date of the impedance and vector fitting technique. It is shown that the parasitic currents and interference voltage in the system can be simulated in the different parts of the prediction model in the conducted frequency range (150 kHz-30 MHz). Experiments have successfully confirmed that the approach is effective.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 학술대회 논문집 전문대학교육위원
• /
• pp.79-82
• /
• 2003

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.