Design of Optimal Structure of AC Superconducting Wire Using 3-D Finite Element Method

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A new method for analyzing 3-D magnetic fields in ac superconducting wires has been developed. The verification of the method for calculating the coupling loss of ac superconducting wire is carried out by comparing the calculated values with measured ones. It is also shown that the opotimal structure of the superconducting wire can be investigated by using the newly developed numerical method. The results obtained can be summarized as follows :1. Development for analyzing 3-D Magnetic Fields in AC Superconducting WiresA new method for analyzing 3-D coupling current in multifilamentary superconducting cable is developed taking efficiently into account the anisotropy of conductivity.2. Pre- and Post-Processors for 3-D AnalysisAs the multifilamentary ac superconducting wire is twisted, ita 3-D mesh is complicated. Then, an efficient graphic system for producing 3-D meshes of ac superconducting wire is developed.3. Measurement of AC LossesThe ac superconducting magnet (60Hz) is produced, and the coupling loss is measured by using the pick-up coil method. It is verified that the ac losscan be divided into hysteresis loss and coupling loss using the two frequency method. The measured coupling loss is compared with the calculated value, and it is shown that the coupling loss is very much affected by the contact resistance between the strands.4. Optimal Structure of AC Superconducting WireThe effects of thestructure of cable and the matrix (CuNi) on coupling losses are investigated. It is shown that the potimal design of ac superconducting wire is possible by using new method developed in this research.