• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.87-89
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• 2005

In this paper, we analyzed that characteristics of flux-lock type superconducting fault current limiter (SFCL) using the third winding to fault current limiting. The flux-lock type SFCL using the third winding consists of the first and seconding windings which are wound in parallel each other a iron core. Also it connected inductively the third winding connected resistance of series. Because of the hysteresis according to the increased voltage, the distortion of current in the flux-lock type SFCL occurs. It is a disadvantage to increase the capacity of SFCL. We conformed that the third winding of the flux-lock type SFCL prevented the distortion of current. Also, the third winding did not affect the initial fault current of the flux-lock type SFCL.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.8
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• pp.62-68
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• 2014

The series connection type superconducting fault current limiter (SFCL) with added third winding, which was magnetically coupled in one iron core, was proposed. The proposed SFCL was expected to be more improved by just adding third winding into the conventional series connection type SFCL with two coils. To analyze the contribution of the third winding for the current limiting and the recovery characteristics of the SFCL, the short-circuit tests for the series connection type SFCL with the added third winding were performed together with the analysis on its electrical equivalent circuit. From the comparative analysis on the amplitude of the limited fault current and the power burden of the high-TC superconducting (HTSC) element comprising this SFCL, the improved current limiting and recovery characteristics of the series connection type SFCL using the third winding could be confirmed.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.213-217
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• 2008

The flux-lock type superconducting fault current limiter(SFCL) can apply the magnetic field into the high-$T_C$ superconducting(HTSC) element by adopting the magnetic field coil in its third winding. To apply the magnetic field into the HTSC element effectively, the capacitor for LC resonance is connected in series with the magnetic field coil. However, the current waveform of third winding for the application of the magnetic field is affected by the LC resonance condition for the frequency of the source voltage and can affect the waveform of the limited fault current. In this paper, the current waveform of the third winding in the flux-lock type SFCL according to LC resonance condition during a fault period was analyzed. From the differential equation for its electrical circuit, the current equation of the third winding was derived and described with the natural frequency and the damping ratio as design parameters. Through the analysis according to the design parameters of the third winding, the waveform of the limited fault current was confirmed to be influenced by the current waveform of the third winding and the design condition for the stable fault current limiting operation of this SFCL was obtained.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.1033-1037
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• 2013

Coercion transformer is commonly used in the electrical grid which in three phase of distribution system. The accident of the electrical grid is divided into a single, a double, a third line-to-ground faults and a double, a third line-to-line faults. A single line-to-ground fault accounts for nearly 75[%] among them. In this research, when a Superconducting Fault Current Limiters (SFCL) was applied to the three phase power system, operation in a single line-to-ground fault and limiting characteristics of fault current according to turns ratio of third winding were analyzed. When a single line-to-ground fault happened, secondary winding's circuit was open. Then third winding's circuit with a SFCL was closed. So fault current was limited by diverted circuit. At this time, we could find out that size of the limited fault current could be changed according to third winding rate. We confirmed that limiting operation of the fault current was carried out within one-period. These results will be utilized in adjusting the size of the SFCL.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.472-477
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• 2017

In this work, the current limiting and recovery characteristics of a flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils were effectively improved by adding a third winding into the conventional flux-lock type SFCL with series connection of two coils. To confirm the contribution of the third winding to the current limiting and recovery characteristics of this type of the SFCL, short-circuit testing was carried out with consideration of the third winding, and the effect of the third winding on the current limiting and recovery characteristics was examined by comparative analysis of the amplitude of the limited fault current and the power burden of the high-TC superconducting (HTSC) element comprising the SFCL. Through the analysis of both the limiting impedance and the operational current as the main design parameter of the SFCL, the improved current limiting and recovery characteristics of the flux-lock type SFCL using the third winding could be verified.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.289-293
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• 2016

The flux-lock type superconducting fault current limiter (SFCL) connects the two parallel windings in parallel with a ferromagnetic core. We suggest that the double quench flux-lock type SFCL should add a third winding. We analyzed characteristics of the fault current and the peak current using the quench of the high-Tc superconducting element. The proposed SFCL's inductances of a primary winding and the third winding were fixed and the amplitude of inductance of the secondary winding was changed. We found that the fault current can be more effectively controlled through the analysis of the equivalent circuit and the short-circuit tests.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.20-26
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• 2014

To enhance torque density by harmonic current injection, optimal slot/pole combinations for five-phase permanent magnet synchronous motors (PMSM) with fractional-slot concentrated windings (FSCW) are chosen. The synchronous and the third harmonic winding factors are calculated for a series of slot/pole combinations. Two five-phase PMSM, with general FSCW (GFSCW) and modular stator FSCW (MFSCW), are analyzed and compared in detail, including the stator structures, star of slots diagrams, and MMF harmonic analysis based on the winding function theory. The analytical results are verified by finite element method, the torque characteristics and phase back-EMF are also taken into considerations. Results show that the MFSCW PMSM can produce higher average torque, while characterized by more MMF harmonic contents and larger ripple torque.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.3
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• pp.330-334
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• 2010

We tried to combine a transformer with a superconducting element and investigated the current limiting characteristics. When a superconducting element was connected to third winding of the transformer, the fault current was limited to about 90 % effectively. The fault current and consumption power were able to be controlled by the turn's ratio of secondary and third windings. It gives flexibility of the rating of a transformer in the power grid. As a result, power burden of a superconducting element was reduced by the decrease of turn's ratio in third winding of a transformer. It was because the voltage behavior of a superconducting element was dependent on turn's ratio of a transformer while the current characteristic was independent.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.30-33
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• 2013

The studies of superconducting fault current limiter (SFCL) for reduction of the fault current are actively underway in the worldwide. In this paper, we analyzed the characteristics of a new type SFCL using the conventional transformer and superconducting elements combined mutually. The secondary and third windings of this SFCL were connected the load and the superconducting element, respectively. The electric power was provided to load connected to secondary windings of the transformer in normal state of power system. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the ripple phenomenon of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the CT(current transformer) and then turn-on and turn-off switching behavior of the SFCL was performed by the SCR(silicon-controlled rectifier). As a result, the proposed SFCL limited the fault current within a half-cycle efficiently. We confirmed that the fault current limitation rate was changed according to the winding ratio of a transformer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1743-1747
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• 2012

The research of superconducting fault current limiter (SFCL) for reduction of the fault current is actively underway in the worldwide. In this paper, we analyzed the characteristics of a SFCL using the transformer and superconducting elements combined mutually in accordance with the fault types. The structure of this SFCL was composed of the secondary and third windings of a transformer connected to the load and the superconducting element, respectively. The provided electric power flew into the load connected to the secondary winding of the transformer in normal state. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the effect of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the current transformer(CT) and then turn-on and turn-off switching behavior of the secondary line in the transformer was performed by the silicon-controlled rectifier(SCR). As a result, the proposed SFCL limited the fault current within one-cycle efficiently. Also, the degradation of the superconducting element in the normal state was avoided.