• Journal of Welding and Joining
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• 제34권3호
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• pp.40-46
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• 2016

The digital controlled SMA welding power source having the hot start current and short circuit waveform control was developed. The inverter power controller was used an analog circuit and the short circuit waveform controller was developed using a 8-bit MCU. For the evaluation of the developed SMA welding power source it were compared with a domestic welding power sources. Using the high titanium oxide type and low hydrogen type electrodes, the characteristics of hot start and short circuit was evaluated. Developed SMA welding power source shows good start performance. Also, arc stability and low current weldability were improved by the short circuit waveform control.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.476-479
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• 2001

Interconnection of new energy sources, such as photovoltaic generation, wind power generation, etc., into the electric power distribution system may result in the increasing short-circuit capacity when a short circuit fault occurs. The short-circuit capacity becomes over the interrupting ratings of circuit breakers, and then they fails to operate in the proper way they prevent fault currents from flowing into the distribution facilities and thus causing them serious damages. This study deals with impacts on the respective short-circuit capacity of both low voltage and extra high voltage distribution systems at which new energy sources are installed. In order to obtain more accurate and all-case values very close to reality in the complicated distribution system, computer simulation tools should be required. In this paper, however, its focus is placed on examining the varying trend of short-circuit capacity, which may happen owing to new energy source interconnection, as a previewing step for exhaustive simulation studies.

• 전력전자학회논문지
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• 제3권4호
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• pp.426-436
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• 1998

Identification of fault current during the operation of a power semiconductor switch and activation of suitable remedial actions are important for reliable operation of power converters. A short circuit is a basic and severe fault situation in a circuit structure such as voltage source converters. This paper presents a new active protection circuit for fast and precise clamping and safe shutdown of fault currents of the IGBTs. This circuit allows operation of the IGBTs with a higher on-state gate voltage, which can thereby reduce the conduction loss in the device without compromising the short circuit protection characteristics. The operation of the circuit is studied under various conditions, considering variation of temperature, rising rate of fault current, gate voltage value, and protection circuit parameters. An evaluation of the operation of the circuit is made using IGBTs from different to confirm the effectiveness of the protection circuit.

• Journal of Welding and Joining
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• 제13권4호
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• pp.75-84
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• 1995

In GMA welding of sheet metal, the short circuit metal transfer mdoe is preferred because of its low heat input and capability of bridging the root gap. The molten electrode is transferred to the workpiece during repectitive short circuit in the model. The waveform of welding current or voltage and the frequency of short circuiting are affected by a number of factors including: magnitude of welding current and voltage, root gap, electrode extension, power supply characteristics, and so on. In this study experimental models were proposed, which are able to determine the relationship between the root gap and short circuit frequency and the relationship between the root gap and appropriate welding speed that produces the good quality of back bead without burn through. Using the experimental models, the root gap can be obtained from measuring the short circuit frequency, and then the appropriate weldig speed to the root gap can be determined. Thus a back bead control system was constructed by controlling the welding speed for maintaining the quality of back bead. The developed system has shown the successful capability of back bead control.

• Journal of Welding and Joining
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• 제16권6호
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• pp.52-58
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• 1998

The effect of Si content in welding wires on th arc stability was investigate, in the region of short circuit transfer and spray transfer. In the region of short circuit transfer, with increasing Si content, average arcing time and average short circuit time were increased. Therefore, droplet transfer frequency was decreased, due to the increase of arcing time and peak current at the moment of arc-reiginition was increased, due to the increase of short circuit time. In the region of spray transfer, the fluctuations of arc current and arc voltage was the most stable in wire with Si content of about 00.60 wt.%.

• Journal of Power Electronics
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• 제16권4호
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• pp.1298-1305
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• 2016

This paper presents the development of a short-circuit protection mechanism on a high voltage switch (HVS) board which is built by a series connection of semiconductor switches. The HVS board is able to quickly detect and limit the peak fault current before the signal board triggers off a gate signal. Voltage clamping techniques are used to safely turn off the short-circuit current and to prevent overvoltage of the series-connected switches. The selection method of the main devices and the development of the HVS board are described in detail. Experimental results have demonstrated that the HVS board is capable of withstanding a short-circuit current at a rated voltage of 10kV without a di/dt slowing down inductor. The corresponding short-circuit current is restricted to 125 A within 100 ns and can safely turn off within 120 ns.

• Journal of Welding and Joining
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• 제17권1호
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• pp.55-61
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• 1999

The effect of S content in welding wires on the arc stability was investigated, in the region of short circuit transfer and spray transfer. In the region of short circuit transfer, with increasing S content, average arcing time and average short circuit time were decreased. Therefore, droplet transfer frequency was increased, due to the reduction of arcing time and peak current at the moment of arc-reiginition was decreased, due to the decrease of short circuit time. In the region of spray transfer, the fluctuation degree of arc current and arc voltage became more stable, with increasing S content.

• 전기학회논문지
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• 제65권7호
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• pp.1186-1192
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• 2016

This paper proposes techniques to diagnose short-circuit faults of both the diodes and power FET in switching mode power supply (SMPS) by using a simple analog tester. The diodes in full-bridge rectifier, power FET, switching transformer, and some sensors are modelled with resistor. The total resistance value measured at the input terminal of a SMPS is analyzed when the short-circuit faults of diodes in a full bridge rectifier or power FET are occurred. The short-circuit faults of one or two diodes in a full bridge rectifier, power FET, and both the diodes in a full bridge rectifier and power FET can be detected by a range of total resistance, which is measured by the analog tester. Through experiments, the theoretical analysis for total resistance under short-circuit faults can be verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1856-1858
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• 2000

This paper describes the principles of reignition system which has newly been developed and used as KERI's high power testing facilities. Synthetic short-circuit testing method is generally adopted to perform the short-circuit test of the ultra high-voltage circuit breakers, which consists of two separated sources such as the current source from short-circuit generator and the voltage source from charged energy in capacitor. And, in case of synthetic short-circuit test, it will be necessary to use the reignition system in order to extending the arcing time of the circuit breaker and provide the arc energy equivalent to the direct testing method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.705-706
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• 2006

Generally Short Circuit Test of transformers are tested according to IEEE std C57.12.00-2000, IEC 60076-5(2000-07), ES148(1998.6.26) or KS C4309(2003). But ES148(1998.6.26) is same as IEEE std C57. 12.00-2000 and KS C4309(2003) is revising coincidence with IEC 60076-5(2000-07). On this study condition of the transformers before short circuit test, calculation method for test current peak value, tolerance on the asymmetrical peak and r.m.s value, short circuit testing procedure, number of short circuit test, duration short circuit test, and detection of faults and evaluation of short circuit test result will be compared with ANSI and IEC.