Reducing AC losses and magnetization in coated conductors is the most important issue for HTS application to electric power devices and magnets. Multifilament structure is a method to reduce AC losses as well as magnetization. From the view point of improving the robustness of a multifilament coated conductor for local normal transitions, it is preferable to have a finite transverse conductance between the filaments because it facilitates current sharing between the filaments. When copper is plated over the superconductor filaments to allow current sharing, the effect of multifilament structure to reduce AC losses and magnetization can be obtained only after the decay of coupling currents flowing through the transverse conductance and the superconductor filaments. To make coupling time constant shorter, we proposed the spiral twist of the copper-plated multifilament coated conductor.

 In this study, we discuss what is required for electromagnetic field analysis model of spiral copper-plated striated coated-conductor cables (SCSC cables). SCSC cables have multiscale configuration: superconductor filaments connected by plated copper, spiral geometry of multifilament coated conductors, and periodic overlap of multifilament coated conductors. Because size of meshes in finite element methods should be defined by the smallest scale, the number of meshes and degree of freedom must be quite huge in the analysis of SCSC cables.

 We started to develop large electromagnetic field analysis model for SCSC cables. To handle large degree of freedom in the analyses, we use hierarchical matrices. The analyzed SCSC cables should not be modelled as cables having infinite length using periodic boundary condition, but as cables having finite length. This is because the analysis model will be used for comparison with experiments and extended to model for coils wound with SCSC cables. In the presentation, we will report analysis results of a finite long and straight SCSC cable as an example. The analysis results will be compared with results by past modelling of infinite long SCSC cables.

This work was supported in part by JST-Mirai Program Grant Number JPMJMI19E1, Japan.

Keywords: electromagnetic field analysis, SCSC cable, multifilament, large-scale simulation