• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.661-662
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• 2006

On the contrary of a conventional motor with very narrow air-gap, it is difficult to calculate the accurate magnetic field distribution and the performance of an air-cored superconducting motor by 2 dimensional analysis, which does not use high permeability material except outer machine shield. This paper aims to do analysis of magnetic field and force distribution from the 3 dimensional modelling of a 1MW class superconducting synchronous motor. Especially, the field coil composed of Bi-2223 high-temperature superconductor and the outer machine shield are modelled by finite element analysis software according to their structures and the self-inductance and Lorentz force are calculated based on the 3 dimensional magnetic field calculation.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.249-251
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• 2008

We investigated a flux-coupling type superconducting fault current(SFCL) limiter. The SFCL consisted of the primary and secondary coils, which were wound in series each other through an iron core. Superconducting unit was connected with secondary coil in parallel. The flux generated from a coil in normal operation is cancelled out by its structure and the zero resistance of the superconducting unit. In this paper. In order to compare the current limiting effects of the SFCL by applied voltage. When a lied voltage was increased, quench time was shortened Fast quench time is important component under the same fault condition because power burden of the SFCL is reduced by that of the superconducting units. The current limiting behavior of flux-coupling type SFCL was dependent upon the applied voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.288-288
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• 2008

The flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO thin films. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO thin film was connected with secondary coil in parallel. In a normal condition, the flux generated from a primary coil is cancelled out by its structure and the zero resistance of the YBCO thin films. When a fault occurs, the resistance of the YBCO thin films was generated and the fault current was limited by the SFCL. In this paper, we investigated the fault current limiting characteristics according to fault current level in the flux-coupling type SFCL. The experiment results that the fault current limiting characteristics was improved according to increase of the fault current level.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.694-697
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• 2009

The separated three-phase flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In this paper, we investigated the current limiting characteristics through winding number of coil 2 and winding direction in the flux-coupling type SFCL. Through the analysis, it was shown that additive polarity condition and lower winding number of coil 2 have advantaged from the point of view of fault current limiting and burned of YBCO coated conductor.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.296-301
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• 2003

A study on the engineering design and numerical thermo-hydraulic analysis for KSTAR TF coil structure cooling system has been conducted. The numerical analyses have been done to verify the engineering design of cooling using the commercial code, FLUENT and in-house code for calculating helium properties which varies with cooling tube's heat transfer. Through the engineering design process based on the steady heat balance concepts, the circular stainless steel tube with inner diameter of 4 mm for TF coil has been selected as cooling tube. From normal operation mode analysis results, total 28 cooling tubes were finally chosen. Also, three dimensional cool down analysis for TF coil with designed cooling tube was satisfied with next three design criteria. First is cooling work termination within a month, second is maximum temperature difference within 50 K in TF coil structure and third is exit helium pressure above 2 bar. Consequently, these cool down scenario results can afford to adopt as operating scenario data when KSTAR facilities operate.

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.49-52
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• 2014

REBCO coated conductor (CC) tapes with superior mechanical and electromechanical properties are preferable in applications such as superconducting coils and magnets. The CC tapes should withstand factors that can affect their performance during fabrication and operation of its applications. In coil applications, CC tapes experience different mechanical constraints such as tensile or compressive stresses. Recently, the critical current ($I_c$) degradation of CC tapes used in coil applications due to delamination were already reported. Thermal cycling, coefficient of thermal expansion mismatch among constituent layers, screening current, etc. can induce excessive transverse tensile stresses that might lead to the degradation of $I_c$ in the CC tapes. Also, CC tapes might be subjected to very high magnetic fields that induce strong Lorentz force which possibly affects its performance in coil applications. Hence, investigation on the delamination mechanism of the CC tapes is very important in coiling, cooling, operation and design of prospect applications. In this study, the electromechanical properties of REBCO CC tapes fabricated by reactive co-evaporation by deposition and reaction (RCE-DR) under transversely applied loading were investigated. Delamination strength of the CC tape was determined using the anvil test. The $I_c$ degraded earlier under transverse tensile stress as compared to that under compressive one.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.723-724
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• 2006

In this study, superconducting coil arrangements and cryostat concept design were conducted for the development of 13.2kV/630A bifilar winding type high temperature superconducting(HTS) fault current limiter(FCL) with YBCO coated conductor(CC) wire. The coil consists of several layers with unique non-inductive solenoid winding method. Six types of HTS coil arrangements were investigated for the optimal insulation design of HTS FCL. And, conceptual design of cryostat was conducted for the decrement of thermal invasion and the prevention of low voltage insulation breakdown in the LHe which is used as pressurization gas in sub-cooling condition of liquid nitrogen(LN2). As the results, it was found that the modified suspended type cryostat with horizontal coil arrangement is beneficial to the insulation design of 13.2kV level bifilar winding type HTS FCL.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.141-143
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• 1995

The design of a 16 tesla/ 45mm bore superconducting magnet is presented. The system consists of an 8.2 tesla(at 4.2K) outer NbTi coil with a bore I.D. of 261mm, a winding O.D. of 453mm and the length of 430mm which is connected in series with a 5.6 tesla(at 4.2K) middle and a 4.7 tesla(at 4.2K) inner insert coil constructed of multifilamentary $Nb_{3}Sn$. The middle and inner insert coil will be reacted after winding. Also, epoxy impregnation will be accomplished at $Nb_{3}Sn$ coils using a low viscosity crack resistant epoxy which is forced into the coil with a series of vacuum and over atmosphere pressure cycle.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.25-29
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• 2009

To reduce the power loss in normal state, non-inductively wound high temperature superconducting (HTS) coils are used for fault current limiter (FCL) application. Non-inductively wound coils can be classified into two types: solenoid type and pancake type. These two types have different electrical and thermal and mechanical characteristics due to their winding structure difference. This paper deals with the current limiting characteristics, magnetic field analysis of the two coils. Simulation using finite element method (FEM) was used to analyze the magnetic field distribution and inductance of the coils. Short circuit test using stabilizer-free coated conductor (CC) was also carried out. We can compare the characteristics of the two types of coil by using the data obtained from simulation and short circuit test. We confirmed the feasibility of FCL application by the analysis about the characteristics of non-inductively wound coil using CC.