• Progress in Superconductivity and Cryogenics
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• v.6 no.1
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• pp.18-21
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• 2004

This paper presents the optimization for shape design of a field coil used High Temperature Superconducting Motor (HTSM). In materials of HTSM, critical current Ic is more sensitive to magnetic fields directed along the axis or the unit cell ($B_{\bot}$). Thus, in the shape design of the HTS magnet. the maximum $B_{\bot}$ should be reduced to limit Ic. In order to reduce the maximum $B_{\bot}$, the shape optimization of the magnet, which is used for the field coil of HTSM, is necessary. It can be accomplished by using Response Surface Methodology (RSM). Finally, the result of RSM is verified by comparison with these experimental results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1041-1049
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• 1994

Longitudimal and transverse normal zone propagations in the superconducting coil are analyzed and propagation velocity is derived from the heat balance equations in the propagating boundary region. The results of applying to the specific superconducting wire show that propagation velocity is linearly proportional to the transport current and increasing ramp current speeds up the longitudinal velocity by 1.22[m/s] under the applied field of 2T. Transient heat transfer has a significant effect on the normal zone propagation velocity and it decreases longitudinal velocity by 5.2[m/s] under the applied field of 2T as being compared to the steady-state heat transfer. Increasing ramp current speeds up the Z-axis transverse propagation velocity by 0.042[m/s] and transverse velocity of R and Z axis is costant regardless of the current flows.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.232-234
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• 1998

Race-track type superconducting coils are used for wiggler magnets of accelerators and field coils of superconducting generators(S.C.G) and so on. The shape is different from ordinary solenoidal type magnet, so the manufacturing situation and conditions become different and moreover according to these results the output characteristics of magnet also becomes different. In this paper we are dealing with race-track type coil design that is inserted into 30(kVA) S.C.G which will be manufactured before we make l(MVA) S.C.G plant. The design procedure is based on two dimensional electromagnetic analysis including laplace equations in cylindrical coordinate.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.263-268
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• 2003

The Electrical insulation design and testing of high temperature superconducting (HTS) coil for high temperature superconducting fault current limiter (HTSFCL) has been performed. Electrical insulating factors of HTS coil for HTSFCL are turn-to-turn, layer-to-layer. The electrical insulation of turn-to-turn depends on surface length, and the electrical insulation of layer-to-layer depends on surface length and breakdown strength of L$N_2$. Therefore, two basic characteristics of breakdown and flashover voltage were experimentally investigated to design electrical insulation for 6.6㎸ Class HTSFCL. We used Weibull distribution to set electric field strength for insulation design. And mini-model HTS coil for HTSFCL was designed by using Weibull distribution and was manufactured to investigate breakdown characteristics. The mini-model HTS coil had passed in AC and Impulse withstand test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.601-604
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• 2003

The magnetic field generated in the iron core, which is required for the magnetic field to link each coil of the flux-lock type reactor, affects the fault current limiting characteristics of the flux-lock type high-Tc superconducting fault current limiter(SFCL). By applying numerical analysis for equivalent circuit of flux-lock type SFCL, the magnetic field induced in the iron core including currents of each coil was investigated. Through the analysis of magnetic field, we have analyzed that the magnetic field linked the 3rd coil, which is wound in the iron core, prevents the saturation of the iron core, but decreases the impedance of the flux-lock type SFCL.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.22-25
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• 2001

The research results on the superconducting magnet for whole body MRI are presented. The magnet consists of main coil with 6 solenoid coils, shielding coil with 2 solenoid coils and 6 sets of cryogenic shim coil. The ferromagnetic shim assembly is installed on the inside wall of the room temperature bore for shimming inhomogeneous field components generated due to manufacturing tolerances, installation misalignments and external ferromagnetic materials near the magnet. Also, the magnet is enclosed with the horizontal type cryostat with 80cm room temperature bore to keep the magnet under the operating temperature. The magnetic field distributions within the imaging volume were measured by the NMR field mapping system. Through the test, the central field of magnet was 1.5 Tesla and the field homogeneity of 9.3 ppm has been obtained on 40cm DSV(the diameter of spherical volume) and using this magnet, comparatively good images for human body, fruits and water phantoms have been achieved.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.186-188
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• 1998

Acoustic emission monitoring on two racetrack superconducting field winding coil was performed during excitation and quenches to diagnose the integrity of the field winding coils. Two field windings were not impregnated with epoxy The results confirm that the acoustic emission signals are mainly due to conductor motions which cause premature quenching of the winding. The quench current of modified racetrack type field winding coil (Type B) are more higher than that of conventional field winding coil (Type A).

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.177-179
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• 2000

In this paper, we analyzed quench characteristics of field windings using 2 dimensional analysis. The quench origin was assumed to take place at the inner most point in the mid-plane of the coil. The temperature distribution was numerically calculated on the coil cross section using FDM analysis, and was used to estimate the normal zone resistance of the coil. Finally, we obtained voltage current characteristics of the quenched winding coils.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.784-785
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• 2008

In general, in most case of high temperature superconducting (HTS) rotating machinery, HTS field coil is rotated. HTS homopolar motor field coil is nat necessary to be rotated and the torque of motor is not strongly related with the field coil. Therefore, HTS homopolar motor has a superior mechanical stability comparing with other HTS rotating machines. These advantages can make the design of HTS field coil and cryostat much more simple. In this paper, HTS field coil was fabricated and tested. Before test, authors habe estimated the critical current of HTS field coil at 77K by simulation using FEA (Finite Element Analysis) software and power law equation. The experiment details and results are presented in this paper, and discussed. The field windings are made with HTS Bi-2223 wire which operates at 77K.

• Progress in Superconductivity and Cryogenics
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• v.22 no.1
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• pp.12-16
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• 2020

As high homogeneity in magnetic field is required to increase the resolution of MRI magnets, various shimming methods have been researched. Using one of them, the design of the superconducting active zonal shim coil for MRI magnets is discussed in this paper. The magnetic field of the MRI magnet is expressed as the sum of spherical harmonic terms, and the optimized current density of shim coils capable of removing higher-order terms is calculated by the Tikhonov regularization method. To investigate all potential designs derived from calculated current density, 4 sweeping parameters are selected: (1) axial length of shim coil zone; (2) radius of shim coils; (3) exact axial position of shim coils; and (4) operating current. After adequate designs are determined with constraints of critical current margin and homogeneity criterion, the total wire length required for each is calculated and the design with a minimum of them is chosen. Using the superconducting wire length of 9.77 km, the field homogeneity over 50 cm DSV is improved from 24 ppm to 1.87 ppm in the case study for 9.4 T whole-body MRI shimming. Finally, the results are compared with the finite element method (FEM) simulation results to validate the feasibility and accuracy of the design.