• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.1
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• pp.12-17
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• 2002

In this paper, an effective ionization coefficient for 4H-SiC is extracted in the form of c .E$^{m}$ from ionization coefficients of electron and hole. Analytical expressions for critical electric field and breakdown voltage of 4H-SiC p$^{+}$n junction are derived by employing the effective ionization coefficient. The analytic results agree well with the experimental ones reported within 10% in error for the doping concentration in the range of 10$^{15}$ cm$^{-3}$ ~10$^{18}$ cm$^{-3}$ . .

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.123-126
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• 2003

고온초전도테이프의 전력부야 응용에서 자화손실과 함께 매우 중요한 통전손실에 대한 실험적 조사 연구를 한 결과, 외부자장이 커짐에 따라서 직류전압이 급격히 증가하였으며, 자장의 세기가 동일할지라도 교류인 경우가 직류인 경우보다 대단히 크다. 그리고 외부교류자장에 대한 직류전압-전류 특성으로부터 정의되는 동저항 또한 외부교류자장의 세기에 따라서 상이하지만 테이프의 임계전류에서 전기저항$(3.7\;{\mu}{\Omega}/m)$과 비교하여 작게는 수배에서부터 크게는 수백 배까지 증가한다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.455-456
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• 2019

본 논문은 태양광 발전시스템에서 일사량이 급변했을 때 최대 전력점(MPP: Maximum Power Point)을 빠르게 추종할 수 있는 P&O(Perturb and Observe)기반 가변 스텝 알고리즘을 제안하였다. 제안한 기법은 일사량 또는 온도에 의해 환경 변화 시 최대 전력점에서의 전압 변화 특성을 이용하며, 가변 스텝 방식이 적용된 전압제어를 통해 MPP를 추종한다. 임계값 설정으로 일사량 급변을 판단하며, MPP를 빠르게 추종하기 위한 고속 모드로 동작한다. MPP에 도달하면 가변 모드로 전환하여 정상상태 오차를 최소화 한다. PV 시뮬레이터와 태양광 전력변환시스템을 통해 제안한 MPPT 알고리즘의 성능을 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.56-63
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• 2003

This paper studies that torque model considered with decaying phase back-EMF is different In conduction and commutation period and analyzes the torque pulsation components mathematically. In this paper, it is proposed a novel method to suppress torque pulsation due to commutation time. First, it propose commutation delay time control method, which is to compensate current slope of rising phase and decaying phase to control commutation time. Current ripple is minimized at non-commutating current and torque ripple is reduced below critical speed range that dc link voltage is the same as four times of back-EMF voltage. However, torque ripple still exists due to the relation with back-EMF and commutating current and it is increased on a large scale above critical speed range, especially. Secondly, proposed method is commutation time control, which is considered with torque pulsation due to the relation of back-EMF and commutating current. Through the proposed method, the torque pulsation can be minimized in the whole speed range as well as range over critical speed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.849-855
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• 2012

The effect of electric fields on the response of diffusion flames in a counterflow has been investigated experimentally by varying the AC voltage and frequency. The result showed that the flame was stationary with high AC frequency above the threshold frequency, and it increased with the applied voltage and then leveled off at 35 Hz. Below the threshold frequency, however, the flame oscillated with a frequency that was synchronized with the applied AC frequency. This oscillation can be attributed to the ionic wind effect due to the generation of bulk flow, which arises from the momentum transfer by molecular collisions between neutral molecules and ions, where the ions in the reaction zone were accelerated by the Lorentz force.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.16-23
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• 2018

Alternative technologies for sludge treatment and disposal need to be developed urgently because the amount of produced production has increased continuously. In this study, Pulsed Electric Fields (PEF) technique was applied for sludge solubilization and the performance was evaluated. The PEF equipped with electrodes coated by epoxy resin and teflon was inducted to the activated sludge suspension, and the effect of the coating materials on the solubilization was determined. In addition, the effect of the applied voltage on the solubilization yield was investigated as the applied voltage was increased from 6 to 12 and 15 kV. Sludge solubilization was not observed when the epoxy-coated electrode was used for PEF induction regardless of the applied voltage. However, sludge solubilization occurred when 12 and 15 kV were applied to the teflon-coated electrodes. The MLSS decreased to 9%, and the soluble-COD increased to 496% when the applied voltage was 15 kV. But sludge solubilization did not happen under 6 kV condition. The corona discharge was observed at applied voltages of 12 and 15 kV, (Ed- sorry but I cannot understand the following highlight) but if 6 kV, strongly indicating that the corona discharge make the sludge solubilized, which suggests that the critical voltage for sludge solubilization lies between 6 and 12 kV. Consequently, proper selection of electrode-coating materials and the applied voltage of PEF could lead to sludge solubilization by corona discharge.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.151-161
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• 2013

An active power factor correction (PFC) circuit is presented which employs a newly proposed input voltage sensor-less control technique operated in continuous conduction mode (CCM) and critical conduction mode (CRM). The conventional PFC circuit with input voltage sensor-less control technique degrades the power factor (PF) under the light load condition due to DCM operation. In the proposed PFC circuit, the switching frequency is basically 70KHz in CCM operation. In light load condition, however, the PFC circuit operates in CRM and the switching frequency is increased up to 200KHz. So CCM/CRM operation of the PFC circuit alleviates the decreasing of the PF in light load condition. The proposed PFC controller IC has been implemented in a $0.35{\mu}m$ BCDMOS process and a 240W PFC prototype is built. Experimental results shows the PF of the proposed PFC circuit is improved up to 10% from the one employing the conventional CCM/DCM dual mode control technique. Also, the PF is improved up to 4% in the light load condition of the IEC 61000-3-2 Class D specifications.

• Journal of the Korea Society for Simulation
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• v.23 no.3
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• pp.27-32
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• 2014

In this paper, We are going to propose the novel structure with improved behavior than the conventional vertical structure for VLSI CMOS circuits. For this, the proposed structure is the moat shape for STI. We want to analysis the characteristics of simulations about the electron concentration distribution, oxide layer shape of hot electron stress, potential flux and electric field flux, electric field fo themal damage and current-voltage characteristics in devices. Physically based models are the ambient and stress bias conditions of TCAD tool. As a analysis results, shallow trench structure were trended to be electric functions of passive as device dimensions shrink. The electrical characteristics influence of proposed STI structures on the transistor applications become stronger the potential difference electric field and saturation threshold voltage, are decreased the stress effects of active region. The fabricated device of based on analysis results data were the almost same characteristics of simulation results data.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.832-833
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• 2008

초전도 한류 소자의 퀜치 특성은 인가 전압의 크기와 시간에 의존한다. 본 연구에서는 사파이어 기판 위에 박막 형태로 증착된 Au/YBCO의 퀜치 거동을 조사하기 위하여 임의 시간의 고장전류를 인가하고 이 때 발생하는 온도를 검출하여 그 특성을 조사하였다. 시험에 사용된 한류소자는 Au/YBCO/사파이어 기판으로 구성되었으며, 길이 19cm, 폭 2 cm의 stripe 형태를 갖는 초전도 박막이었다. 임계전류는 200A이며 6 주기 동안의 전압인가에 대하여 6 V/cm (상승온도 250 K 기준)의 정격전압을 보였다. 이러한 특성을 갖는 한류소자의 한류 시 온도증가를 조사하기 위하여 한류소자의 뒷면에는 은 박막을 적절한 패턴으로 증착하여 온도 센서로 사용하였으며, 이를 통하여 퀜치 거동을 파악하고자 하였다. 실험 결과, 한류 소자 양단에 250 V의 전압을 인가하고 2 ms 동안 사고 전류를 인가하였을 때, 초전도 박막의 온도는 154 K까지 증가하였으며 다시 초전도성을 회복하기까지의 시간은 약 420 ms가 소요됨을 확인할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.553-556
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• 2003

금속유기물 용액 증착법(MOD)법은 금속유기물 용액을 스핀 코팅하여 고온 열처리를 통해 대면적의 고온 초전도 박막을 만들 수 있으며, 고가의 진공 시스템이 필요하지 않기 때문에 매우 경제적인 박막 증착 방법이다. 본 연구에서는 MOD법을 이용해서 고온초전도체 마이크로파 필터나 터널접합 소자와 같은 전자 소자 응용 연구를 위해 요구되는 높은 임계전류 특성을 갖도록 박막 성장 조건을 변화시켜서 제작된 고온 초전도체 Bi2Sr2CaCu2O8+d (BSCCO2212) 박막을 제작하였다. 박막 특성은 x-ray diffraction (XRD), scanning electron microscope (SEM)으로 표면적, 구조적 특성을 관찰하고 저항-온도 (R-T) 변화 및 전류-전압 (I-V) 특성 측정을 통해 전기적 특성을 연구하여 임계전류를 향상 시킬 수 있는 박막제작 조건에 관해 논의하였다.