• Journal of Magnetics
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• v.21 no.3
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• pp.413-420
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• 2016

The permanent magnet synchronous motor has high efficiency driving performance and high power density output characteristics compared with other motors. In addition, it has good regenerative operation characteristics during braking and deceleration driving condition. For this reason, permanent magnet synchronous motor is generally applied as a power train motor for electrical vehicle. In permanent magnet synchronous motor, the most probable causes of fault are demagnetization of rotor's permanent magnet and short of stator winding turn. Therefore, the demagnetization fault of permanent magnet and turn fault of stator winding should be detected quickly to reduce the risk of accident and to prevent the progress of breakdown of power train system. In this paper, the fault diagnosis method using high frequency low voltage injection was suggested to diagnose the demagnetization fault of rotor permanent magnet and the turn fault of stator winding. The proposed fault diagnosis method can be used to check the faults of permanent magnet synchronous motor during system check-up process at vehicle starting and idling stop mode. The feasibility and usefulness of the proposed method were verified by the finite element analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.499-504
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• 2016

In this paper, we analyzed the operational characteristics of the fault current limiting according to the amplitude of the fault current for the transformer type superconducting fault current limiter (SFCL). If the fault current happens, the superconducting element connected to the secondary coil is occurred quench and the fault current is limited. When the larger fault current occurs, the superconducting element connected to the third coil is occurred additional quench and the peak fault current is limited. We found that the fault current can be more effectively controlled through the analysis of the fault current limiting and the short-circuit tests.

• Journal of Power Electronics
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• v.17 no.1
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• pp.242-252
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• 2017

This paper deals with the blocking of DC-fault current during DC cable short-circuit conditions in HVDC (High-Voltage DC) transmission systems utilizing Modular Multilevel Converters (MMCs), where a new SubModule (SM) topology circuit for the MMC is proposed. In this SM circuit, an additional Insulated-Gate Bipolar Translator (IGBT) is required to be connected at the output terminal of a conventional SM with a half-bridge structure, hereafter referred to as HBSM, where the anti-parallel diodes of additional IGBTs are used to block current from the grid to the DC-link side. Compared with the existing MMCs based on full-bridge (FB) SMs, the hybrid topologies of HBSM and FBSM, and the clamp-double SMs, the proposed topology offers a lower cost and lower power loss while the fault current blocking capability in the DC short-circuit conditions is still provided. The effectiveness of the proposed topology has been validated by simulation results obtained from a 300-kV 300-MW HVDC transmission system and experimental results from a down-scaled HVDC system in the laboratory.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.100-105
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• 2022

This paper applies the arc detection algorithm to prevent the false detection in photo voltaic series arc detection circuit, which is required not only to detect the series arc quickly, but also not falsely detect the arc for the non-arc noise. For this purpose, this study proposes a rapid and preventive false detection method of single peak noise and short noise signals. First, to prevent false detection by single peak noise, Discrete wavelet transform (DWT)-based characteristic parameters are applied to determine the shape and the amplitude of the noise. In addition, arc fault detection within a few milliseconds is performed with the DWT iterative algorithm to quickly prevent false detection for short noise signals, considering the continuity of serial arc noise. Thus, the method operates not only to detect series arc, but also to avoid false arc detection for peak and short noises. The proposed algorithm is applied to real-time serial arc detection circuit based on the TMS320F28335 DSP. The serial arc detection and peak noise filtering performances are verified in the built simulated arc test facility. Furthermore, the filtering performance of short noise generated through DC switch operation is confirmed.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1305-1309
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• 2013

The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL's application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

• 전기의세계
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• v.25 no.5
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• pp.75-78
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• 1976

The most difficult problem encountered in impulse test of transformer is the determination of exact fauly for coil layer short. This paper is to establish one of improved standards in the above case by means of wave form analysis, based on the equivalent circuits and experimental investigation. During the fault occurs, the local oscillation in fault circuit is applicable where as the reflection wave is utilized to the main circuit. The result current wave form at neutral impeadance point is similar to the wave form by impulse test and has the singular wave form respectively.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.14-17
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• 1996

We analyzed the characteristics of a power system with superconducting fault current limiter and showed the possibility of the application of a superconducting fault current limiter to a real power system through manufacturing of and experiment about 220Vrms/100Apeak class superconducting fault current limiter. We experimentally confirmed that the overvoltage of superconducting fault current limiter increased as the rate of current sharing to the limiting coil grew. The fault current could be limited within a few milliseconds when it was applied to a power system in series. Therefore, we could confirm that superconducting fault current limiter was effective in protection of a substation or power plant at short-circuit fault. (author). 7 refs., 7 figs., 2 tabs.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.9-13
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• 2007

Coated conductor(CC) is recently in actively progress for the research and development, and its can be used various stabilizer lot the specific requirements for each application. Among various superconducting applications, coated conductor applied to superconducting fault current limiters(SFCLS) bypasses fault current to its stabilizer, where the surge is abruptly reduced ; thus, stainless steel, which has large resistivity can be a suitable stabilizer for SFCLS. Despite high n-value of the YBCO, CC stabilized with stainless steel did not effectively limit the first peak fault current. In the short circuit test results of AMSC's 344S, a half period delay was observed between the fault and the generation of resistance(60Hz). In this paper, we performed short-circuit experiments with stacked and unstacked CC and compared the test results to analyze effective fault current limiting characteristics. we compared time of the generated resistance as the fault current limiting characteristics and made the samples one is the stacked CC and the other is unstacked CC. These samples were used equal numbers of pieces of CC. In addition, comparison and analysis was made for the stacked structure by measuring fault current limiting characteristics with respect to thermal insulation by impregnating with epoxy resin.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2342-2348
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• 2009

Even though underground transmission cable is an essential transmission method to supply stable power for downtown and population center, the interaction of electromagnetic force by fault current is very large comparing to overhead transmission line due to restricted installation space such as tunnel, and close consideration is required for it. This paper presents countermeasures to reduce and release the effect of electromagnetic force with rope binding and installation of spacer and describes its efficacy through three phase short-circuit test, which will be utilized as basic materials for improvement and development of cleat, hanger, etc. to reduce and release effect of electromagnetic force in the future.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1272-1280
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• 2014

This paper presents solutions for fault detection and diagnosis of two-level, three phase voltage-source inverter (VSI) topologies with IGBT devices. The proposed solutions combine redundant standby VSI structures and contactors (or relays) to improve the fault-tolerant capabilities of power electronics in applications with safety requirements. The suitable combination of these elements gives the inverter the ability to maintain energy processing in the occurrence of several failure modes, including short-circuit in IGBT devices, thus extending its reliability and availability. A survey of previously developed fault-tolerant VSI structures and several aspects of failure modes, detection and isolation mechanisms within VSI is first discussed. Hardware solutions for the protection of power semiconductors with fault detection and diagnosis mechanisms are then proposed to provide conditions to isolate and replace damaged power devices (or branches) in real time. Experimental results from a prototype are included to validate the proposed solutions.