• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.3
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• pp.214-221
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• 2021

SiC MOSFETs require a faster and more reliable short-circuit protection circuit than conventional methods due to narrow short-circuit withstand times. Therefore, this research proposes a short-circuit protection circuit using a current-sensing circuit based on Rogowski coil. The method of designing the current-sensing circuit, which is a component of the proposed circuit, is presented first. The integrator and input/output filter that compose the current-sensing circuit are designed to have a wide bandwidth for accurately measuring short-circuit currents with high di/dt. The precision of the designed sensing circuit is verified on a double pulse test (DPT). In addition, the sensing accuracy according to the bandwidth of the filters and the number of turns of the Rogowski coil is analyzed. Next, the entire short-circuit protection circuit with the current-sensing circuit is designed in consideration of the fast short-circuit shutdown time. To verify the performance of this circuit, a short-circuit test is conducted for two cases of short-circuit conditions that can occur in the half-bridge structure. Finally, the short-circuit shutdown time is measured to confirm the suitability of the proposed protection circuit for the SiC MOSFET short-circuit protection.

• Journal of Welding and Joining
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• v.23 no.5
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• pp.14-19
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• 2005

In high speed $CO_2$ welding, it has been blown to produce no sound bead with undercut or humping bead. In this study welding phenomena through synchronized high speed camera and output welding voltage and current waveform has been analyzed. For the purpose to improve a welding bead, effect of short circuit current rise slope has been examined. With commercial power source it was produced no sound bead by instantaneous short circuit, long arc period and stubbing at welding speed 2.5mm/min Humping bead or undercut were showed by instantaneous short circuit and long arc period. Also, the weld bead was not formed during the long short circuit period after stubbing start and long arc extinguishment period after wire sticking by failure of arc regeneration, because the droplet was not transferred to weld pool. With increasing short circuit current rise slope the frequency of stubbing was decreased and the normal short circuit rate was increased. A control of short circuit current rise slope was effective factor in high speed welding.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.339-347
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• 2022

This study proposes the mitigation method for overcurrent and oscillation motor current in an active short-circuit operation. This operation is attracting attention as the safe state of electric vehicle traction inverters. However, the active short-circuit operation generates oscillation and overcurrent of motor currents during a transient state. The proposed method uses two different safe states in PMSM, such as active short circuit and freewheeling. The active short circuit is used for safe state in a steady state. To reduce the overshoot and oscillation, a freewheeling state is injected between active short-circuit operation by comparing the motor phase current with an analytically calculated steady-state motor current. Freewheeling state is only used in a transient state. The performance is demonstrated through simulations and experimental results. The peak current of the motor was reduced from 52 A to 40 A, and oscillation time was reduced.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.12-18
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• 2014

This paper analyzes how to calculate the three phase short circuit current calculation procedures used in the IEC 60909 short circuit. It presented the new procedure of the fault current for the interrupting capacity of the circuit breaker. This procedure is applied to the future power system and calculates the fault current. Power demands are increased because of the growth of the economy for this reason, the fault current of the power system is largely increased and the fault current procedure for the proper interrupting capacity calculation of the existing or the new circuit breaker is essential. How to calculate the three phase short circuit current for ac electrical system and select the high voltage and low voltage circuit breaker based on IEC 60909 standards.

• Journal of Power Electronics
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• v.16 no.4
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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.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.473-476
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• 2010

In this paper, we analyzed the short circuit current of a low voltage direct current distribution system. For the analysis, we performed the modeling of the low voltage direct current distribution system with a 6-pulse three-phase thyristor rectifier using the PSCAD/EMTDC, surveyed impedance of sources, transformers and distribution lines to run a simulation. A result of the simulation is that short circuit currents of the direct current distribution system with the rectifier decreased due to a thyristor-ON-resistance(Ron). But in case of the low thyristor-ON resistance, output fault current of the rectifier increased over three-phase short circuit current of an AC power system without a rectifier by regular ratio of the rectifier. Because the output fault current of the rectifier can increase over interrupting the capacity of circuit breakers, studying short circuit currents of a low voltage direct current distribution system with a rectifier is necessary for introducing the direct current distribution systems.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.170-175
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• 2008

This paper describes the exact short-circuit current calculation technique for the single-phase transformer which is installed in the three-phase systems and shorted in the secondary side. Not only the results for a short-circuit current calculation in the existing literatures are wrong, but also little literature deals with the short-circuit current for a single-phase transformer. So, this paper presents a theoretical study and calculation method for a single-phase short current. The validity of the presented method is investigated through Simulation using "Power Tools" and "PSim" program.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.970-973
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• 2003

Abstract An idea to redce the direct-path short circuit current of the CMOS digital integrated circuit is present. The sample circuit model of the CMOS digital circuit is the CMOS current-control digital output driver circuit, which are also suitable for the low voltage supply integrated circuits as the simple digital inverter, are present in this title. The circuit consists of active MOS load as the current control source, which construct from the saturated n-channel and p-channel MOSFET and the general CMOS inverter circuits. The saturated MOSFET bias can control the output current and the frequency response of the circuit. The experimental results show that lower short circuit current control can make the lower frequency response of the circuit.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.700-702
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• 2005

The most electrical apparatus should be able to withstand short-time current and peak current during a specified short time until circuit breakers have interrupted fault current. It defines the short-time withstand ability of electric a apparatus to be remain for a time interval under high fault current conditions. It is specified by both dynamic ability and thermal capability. KERI(Korea Electrotechlology Research Institute) recently constructed the new short-time current and low voltage short circuit testing facilities. This paper shows short- circuit calculation of transformer and describes high current measuring system, and evaluate the result of short-time withstand test used in $3{\phi}$ 90MVA short-time current testing facilities.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1789-1794
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• 2014

This paper suggests an application method for a superconducting fault current limiter (SFCL) using an evaluation index to estimate the risk regarding the short-circuit capacity of the circuit breaker (CB). Recently, power distribution systems have become more complex to ensure that supply continuously keeps pace with the growth of demand. However, the mesh or loop network power systems suffer from a problem in which the fault current exceeds the short-circuit capacity of the CBs when a fault occurs. Most case studies on the application of the SFCL have focused on its development and performance in limiting fault current. In this study, an analysis of the application method of an SFCL considering the risk of the CB's short-circuit capacitor was carried out in situations when a fault occurs in a loop network power system, where each line connected with the fault point carries a different current that is above or below the short-circuit capacitor of the CB. A loop network power system using PSCAD/EMTDC was modeled to investigate the risk ratio of the CB and the effect of the SFCL on the reduction of fault current through various case studies. Through the risk evaluations of the simulation results, the estimation of the risk ratio is adequate to apply the SFCL and demonstrate the fault current limiting effect.