• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.378-381
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• 2002

This paper describes a novel multilevel ad/dc power converter suitable for the protection of frequent output short-circuit. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there is no overshoot of the do voltage because the dc output capacitors keep undischarged state. Analysis and simulations are carried out to investigate the operation and usefulness of the proposed scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.652-658
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• 2006

This paper deals with an electronic ballast for hish intensity short-arc discharge lamps, which consists of a boost converter, a step down converter operated as a current source with power regulation and a low frequency inverter with external ignition circuit The ignition circuit generates high voltage pulses of 130[Hz] up to 5 [kV]. A reignition circuit is equipped in the ballast, and it operates the lamp at a regular interval for protection when an ignition fails. Acoustic resonance phenomenon was eliminated by operating a low frequency square wave voltage and current. The measured lamp voltage, current and consumption power were 123.8 [V], 8.1 [A] and 1,002 [W], respectively. From the experiment, we confirmed that the prototype ballast operates the lamp with a constant power.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.61-68
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• 2011

The circuit breaker of power distribution board is essential part for the protection of electrical disaster from load short, trouble of power system. For the normal operation of circuit breaker, trip coil of the circuit breaker can cut the mechanical contact of circuit breaker from the detection of power system troubles. This paper presents a design and experimental results of trip coil fault detection system for the real time monitoring of the circuit breaker. The designed system is consisted by the trip coil fault detector which is connected to the each circuit breaker and remote monitoring unit. The trip coil fault detector can detect the impedance and operating voltage of the trip coil, and the detected values are compared with the normal state. And the remote monitoring unit can be connected to the 32 channels of trip coil fault detectors by serial communication. From the designed system, the fault and normal states of the trip coil can be remotely monitored in real time. The designed system is verified by the practical circuit breaker of power distribution board. And the results shows the effectiveness of the designed system.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.4
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• pp.387-392
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• 1997

This paper describes a combination surge generator for carrying out performance tests on the surge protection circuits of shipboard electrical systems. Pspice simulations were performed to decide the values of the parts required and to analyze the characteristics of the generator circuitry. The surge generator fabricated can produce four of the most common surge test waveforms : the O.5i/S/100kHz Ringwave, the 1.2/50$\mu$S voltage, the 8/20$\mu$S current, and the lO/lOOOi/S voltage wave¬forms specified in ANSI Std. C62. Source impedances of the surge generator are 12$\Omega$ in the O.5$\mu$S/100kHz mode, O.5$\Omega$ in the 1.2/50$\mu$S and 8/20$\mu$S mode, and 40$\Omega$in the l0/1000$\mu$S mode, and are determined by the ratio of the maxi¬mum open - circuit voltage to the maximum short - circuit current. Experimental results show that the surge generator provides most of the outputs required for the testing of the surge protection circuits on shipboard electrical systems.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.90-95
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• 2015

This paper describes IEC 61727 standard of Photovoltaic (PV) systems -Characteristics of the utility interface. IEC 61727 standard tests include utility compatibility and personnel safety and equipment protection of PV inverter performance functions. Especially utility compatibility part includes test items of 1) voltage, current and frequency, 2) normal voltage operating range, 3) flicker, 4) DC injection, 5) normal frequency operating range, 6) harmonics and 7) waveform distortion, 8) power factor of PV inverter. Also personnel safety and equipment protection part includes test items 1)loss of utility voltage, 2)over/under voltage and frequency, 3)Islanding protection, 4)response to utility recovery, 5)earthing, 6)short circuit protection, 7)Isolation and switching of PV inverter. In this paper, each item of IEC 61727 standard test is studied and analyzed and finally full tested by PV inverter performance function.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.4
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• pp.433-439
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• 2015

Enclosures for CCTV internal short circuit are prevented due to wetting to maintain a constant humidity and temperature, to avoid condensation due to temperature difference, a constant temperature and humidity requirements of the equipment, such as high-temperature resistant and a constant temperature of the structure, degree of energy utilization is optimized for developing this corresponding housing automatic control system and humidity is required. Device being an expensive imaging equipment in side of the enclosure according to the temperature conversion from a hazard protection, there is a need for a constant temperature and humidity control apparatus that can prevent a short-circuit failure. This is a system in which the accessory device is absolutely required for the storage and transmission of an image in recording reliability and field conditions.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.608-611
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• 1989

The full-bridge series resonant converter is analyzed to limit the maximum values of the current and the voltage across resonant capacitor in the case of load short. If the converter is operated in the optimal region derived in this paper, the maximum value of short-circuit current will be smaller or equal to that of the current in steady operation. Since the additional facilities for the protection against load short do not need, converters have advantages in weight, size, and cost.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1313-1317
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• 2013

With increasing demand of power, the equipment of power system is enlarging and the absolute capacity is going up. As a result, when a fault occurs, the fault current is consistently increasing. Therefore, I suggested some solution for limiting the fault current more efficiently. This study shows the characteristics of superconducting limiting elements and normal conducting elements combined with a transformer. We performed a short-circuit test about the fault current by using SCR switching control system operated from a CT. When short circuit accidents happened in the secondary side of a transformer, fault currents flowed and a SCR switching control system was operated. It resulted in a decrease of the fault current in the limited elements of third winding connected in parallel. For this test, we used YBCO thin films and normal conducting elements as the limited elements. Within a cycle, a superconducting fault current limiter with YBCO thin films reduced more than 90% of fault current because the resistance of superconducting elements sustainedly grew. On the other hand, the limiter with normal conductors limited as much as a set value because its resistance characteristic was linear. Consequently, in case of the limiter with superconductor, limiting range of the circuit was wide but the range of protective detection was undefined. In contrast, as for the limiter with normal conductors, limiting range and protection duty were appropriate.

• Journal of Power System Engineering
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• v.4 no.1
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• pp.45-50
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• 2000

Circuit breakers have traditionally employed mechanical methods to interrupt excessive currents. According to power semiconductor technology advances in power electronic device, some mechanical breakers are replaced with solid state equivalents. Advantages of the contactors using semiconductor devices include faster fault interrupting, fault current limiting, no arc to contain or extinguish and intelligent power control, and high reliability. This paper describes the design of a static $100{\pm}10%V$ and 0 to 50A DC self-protected contactor with 85A "magnetic tripping" and 100A interruption current at $2.2A/{\mu}s$ short circuit of load condition using a new power device the HARRIS MCT (600V-75A). The self-protection circuit of this system is designed by the classical ZnO varistor for energy absorption and turn-off snubber circuit ("C" or "RCD") of the MCT.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.55-59
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• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.