Relation between inter-sub-cable contact resistance and coupling loss in multiple-stage stranded cable

Abstract

AC losses in superconducting multi strand cables, those that are used in large scaled applications, e.g. fusion, are governed by contact resistances between the strands. Especially, in the cable with multiple-stage twisting, a variety of magnetic field diffusion time constants exist and these correspond to the quantities of inter-strand coupling losses in each cabling stage. The rate of magnetic field change is less than several T's in usual fusion machines. In this condition, the magnetic field penetrates well into the cable and the coupling current circuit with the larger time constant shows larger AC loss. Here, the time constant is equal to the leakage inductance divided by resistance along the coupling current loop. Therefore, evaluating the coupling current in the larger loop, which consists of a higher twisting stage, e.g., usually the final cabling stage, loss in the whole cable could be expected. The leakage inductance between sub-cables could be estimated considering electrical centers of them. On the other hand, inter-sub-cable contact resistances have not been evaluated until now. In this study, by establishing the inter-sub-cable contact resistance model, the AC loss in the cable with multiple cabling stage was evaluated numerically. We discussed the modeling of contact resistance between sub-cables intensively.