• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권12호
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• pp.584-590
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• 2002

Crowbar system is usually applied to a pulsed power system in which a capacitor bank is discharged into a load. This provides a free wheeling path for the load current and prevents the capacitor from recharging due to a reverse voltage. Usually diodes have been used as a crowbar switch, but it is not a practical system because the cost of the diodes goes up enormously with increasing the system voltage and current. This paper presents a novel protection scheme of a charging and discharging system of a 300 kJ capacitor bank using a low-cost crowbar system which consists of a crowbar switch and resistors. Triggered vacuum switch(TVS) was used for a crowbar switch, and Rogowski coil was used to determine a trigger time of TVS. When this crowbar system is applied to our pulsed power system which consists of capacitor bank($123muF$), inductor() for forming a pulse, load resistor$(100 m\Omega)$, and a closing switch, instantaneous reversal voltage of capacitor bank could be limited less than 1.8 ㎸ until capacitor bank was charred to 17 ㎸.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.286-292
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• 2014

This paper presents the parameters optimization technology for generating the first short stroke lightning current waveform($10/350{\mu}s$) which is necessary for the performance tests of components of lightning protection systems, as required under IEC 62305 and the newly amended IEC 62561. The circuit using the crowbar device specified in IEC 62305 was applied to generate the lightning current waveform. To find the proper parameters of the circuit is not easy because the circuit consists of two parts; circuit I, which relates to the front of current waveform, and circuit II, which relates to the tail. A simulation in PSpise was carried out to find main factors related to the front and tail of $10/350{\mu}s$. The lightning current generator was developed by utilizing the circuit parameters found in the simulation. In the result of experiments, new parameters of the circuits need to be changed because of the difference between the simulation and the experiment results. Using the iterative method, the optimized parameters of the circuits was determined. Also a multistage-type external coil and a damping resistor were proposed to make the efficiency of generation to enhance. According to the result in this paper, an optimized first short stroke lightning current waveform was obtained.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권7호
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• pp.327-334
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• 2003

We have investigated the quench behavior of the series connection of resistive type superconducting fault current limiter (SFCL) components based on YBCO films. Equal shunt resistors $R_s$ across individual SFCL components successfully produced simultaneous Quenches for 5 components in series, resulting in equal application of voltage to all components. If the two components having the highest and the lowest critical currents ($I_c$) quench safely, others quench altogether The highest shunt resistance is to guarantee the safe quenches of all components, leading to the equal voltage applications within the first half cycle after a fault in the short circuit test. The highest $R_s$ was found to be 28 ［$\Omega$］ for the components in the given quench environment. Considering the safe quenches and protection coordination, the optimal $R_s$ was suggested to be approximately a half of the highest $R_s$,, allowing wide selection of $R_s$ and $I_c$'s. This design provides a practical wav of connecting small SFCL components in series for high voltage application.

• 센서학회지
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• 제16권6호
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• pp.407-412
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• 2007

For $VO_{2}$ sensors applicable to temperature measurement by using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were investigated systematically as a function of the annealing condition. The starting materials, vanadium pentoxide ($V_{2}O_{5}$) powders, were mixed with vehicle to form paste. This paste was screen-printed on $Al_{2}O_{3}$ substrates and then $VO_{2}$ thick films were heat-treated at $450^{\circ}C$ to $600^{\circ}C$, respectively, for 1 hr in $N_{2}$ gas atmosphere for the reduction. As results of the temperature vs. resistance property measurements, the electrical resistance of the $V_{2}O_{5}$ sensor in phase transition range was decreased by $10^{3.9}$ order. The presented critical temperature sensor could be used in fire-protection and control systems.

• 한국산학기술학회논문지
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• 제18권9호
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• pp.42-51
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• 2017

본 논문에서는 전기자동차 배터리의 충전 방안 중 하나로 여겨지는 무선전력전송을 이용할 경우 발생 가능한 보호협조 문제점을 분석한다. 전기충전을 위한 무선전력전송 시스템을 구축하기 위해서는 전원공급장치 개발이 필수적이나, 전원공급장치의 정확한 설치기준이 없기 때문에 운용 시 보호협조 상에 문제점이 발생 할 수 있다. 따라서 본 논문에서는 PSCAD/EMTDC로 무선전력전송 전기충전설비용 전원공급장치를 모델링하여 가능성 있는 사고를 모의해보고, 이를 해결할 수 있는 대안을 제시하고자 한다. 즉, 사고 발생 시, 전원공급장치의 60Hz 대역에서 정격차단용량(12.5kA) 상회 가능성과 20kHz 대역에서의 임피던스 병렬화로 인한 보호기기의 부동작 가능성을 시뮬레이션을 통해 확인하였고, 이에 대한 해결책으로 대칭좌표법을 이용한 사고해석 알고리즘과 사고전류를 저감시킬 수 있는 NGR 산정 알고리즘을 제안하였다. 이를 통해 60Hz 대역에서는 NGR(Neutral Ground Resister)을 도입하여 사고전류를 정격차단용량 이하로 저감시키고, 20kHz 대역에서는 중선선에 CT 설치 및 이에 대한 보호정정을 통해 보호기기 부동작이 방지됨을 확인하였다.

• 전력전자학회논문지
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• 제24권6호
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• pp.411-418
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• 2019

Light-triggered thyristors (LTTs) are essential components in high-power applications, such as HVDC transmission and several pulsed-power applications. Generally, LTT fabrication includes a deep diffusion of aluminum as a p-type dopant to form a uniform p-base region, which needs careful concern for contamination and additional facilities in silicon semiconductor manufacturing factories. We fabricated 4-inch 5,000 V LTTs with boron implantation and diffusion process as a p-type dopant. The LTT contains a main cathode region, edge termination designed with a variation of lateral doping, breakover diode, integrated resistor, photosensitive area, and dV/dt protection region. The doping concentration of each region was adjusted with different doses of boron ion implantation. The fabricated LTTs showed good light triggering characteristics for a light pulse of 905 nm and a blocking voltage (V_DRM) of 6,500 V. They drove an average on-state current (I_TAVM) of 2,270 A, peak nonrepetitive surge current (I_TSM) of 61 kA, critical rate of rise of on-state current (di/dt) of 1,010 A/㎲, and limiting load integral (I²T) of 17 MA²s without damage to the device.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.86-88
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• 1997

The detection of the normal zones in the coil winding and the initiation of the proper dump sequence have been one of the most important areas in the superconducting magnet technology. In this paper, the process to derive optimal dump sequence has been investigated through quench simulation and analysis of magnetically coupled superconducting magnet system. The magnet terminal voltage and maximum temperature rise in the quench initiated point are calculated with respect to various input variables such as operation current, dump resistance, etc. The experimental system is comprised of sc solenoidal coil, data aquisition device, external circuit breakers and dump resistor. The quench behavior of the magnet(e.g., temperature profile and the voltage signal) was measured. From this results, theoretical predictions were found to coincide with the experimental observations.

• 센서학회지
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• 제23권5호
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• pp.337-341
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• 2014

For various additives doped-$VO_2$ critical temperature sensors using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were systematically investigated. As a starting material of $VO_2$ sensor, vanadium pentoxide ($V_2O_5$) powders were used, and CaO, SrO, $Bi_2O_3$, $TiO_2$, and PbO dopants were used, respectively. The $V_2O_5$ powders with dopants were mixed with a vehicle to form paste. This paste was silk screen-printed on $Al_2O_3$ substrates and then $V_2O_5$-based thick films were heat-treated at $500^{\circ}C$ for 2 hours in $N_2$ gas atmosphere for the reduction to $VO_2$. From X-ray diffraction analysis, $VO_2$ phases for pure $VO_2$, and CaO and SrO-doped $VO_2$ thick films were confirmed and their grain sizes were 0.57 to $0.59{\mu}m$. The on/off resistance ratio of the $VO_2$ sensor in phase transition temperature range was $5.3{\times}10^3$ and that of the 0.5 wt.% CaO-doped $VO_2$ sensor was $5.46{\times}10^3$. The presented critical temperature sensors could be commercialized for fire-protection and control systems.

• 조명전기설비학회논문지
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• 제22권10호
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• pp.8-17
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• 2008

본 논문에서는 선박용 HID조명의 방전 개시전압을 조절함으로써 초기 방전전류를 억제하여, HID조명의 안정적인 점등이 가능한 제어방식을 제안하였다. 제안된 제어 방식은 방전 대기전압까지 출력전압을 상승시킨 후, 충전전압의 저항부하 방전을 통하여 전압을 감소시키면서, 설계된 방전개시전압시점에서 이그니터를 점화하여 방전 개시 전류를 제한한다. 방전 후 정상상태에서는 정전류 제어로 조도를 제어하게 된다. 제안된 방식은 별도의 전압제어기를 포함하지 않으면서도, 방전개시 시점을 조절할 수 있으므로, 초기 방전 전류를 크게 제한할 수 있으므로, 안정적인 점등과 조명의 수명을 확대할 수 있는 장점이 있다. 또한 조명의 이상상태를 간단한 이상검출 회로를 통하여 순시적으로 감시하여 전체 시스템의 보호 성능을 개선하였다. 제안된 제어기는 실제 선박용 2.5[kW]급의 HID 탐사조명에 대한 실험을 통하여 검증하였다.

• 전기학회논문지
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• 제65권8호
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• pp.1340-1346
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• 2016

Utilization of Distributed Generations (DGs) using Renewable Energy Sources (RESs) has been constantly increasing as they provide a lot of environmental, economic merits. In spite of these merits, some problems with respect to voltage profile, protection and its coordination system due to reverse power flow could happen. In order to analyze and solve the problems, accurate modeling of DG systems should be preceded as a fundamental research task. In this paper, we present a PhotoVoltaic (PV) generation system which consists of practical PV cells with series and parallel resistor and an inverter for interconnection with a main distribution system. The inverter is based on controllable current source which is capable of controlling power factors, active and reactive powers within a certain limit related to amount of PV generation. To verify performance of the model, a distribution system based on actual data is modeled by using ElectroMagnetic Transient Program (EMTP) software. Computer simulations according to various conditions are also performed and it is shown from simulation results that the model presented is very effective to study DG-related researches.