Analyses for inter-strand coupling loss in multi-strand superconducting cable with distributed contact resistance between strands

Multi-strand superconducting cables are utilized to large superconducting m achines and/or alternative or pulse current ones, such as fusion machines a nd superconducting magnetic energy storages (SMESs). We have been studying for electromagnetic phenomena in multi-strand superconducting cables by usi ng both analytical and experimental methods aiming at such large-scale appl ications. When we are going to evaluate alternating current (AC) loss numer ically, especially inter-strand coupling loss, it is important to establish the model of crossover contact resistance distribution between strands and /or sub-cables. For the cable with multiple cabling stages, the contact res istances between two strands (or two sub-cables) change drastically due to the traces of them. They contact well each other at the places where they a re crossover. On the other hand, when they are separated, there is no direc t contact between them. The relation between AC loss and DC contact resista nce was evaluated for a short sample, which is a 3 x 3 cable with Cr plated Nb3Sn strands. The AC loss was measured by the calorie metric method at LH e temperature. The contact resistances between two strands were also measur ed for the same sample in the same condition. Adapting measured contact res istance distribution to the numerical model, the AC loss calculation was fu lfilled by using the distributed constant electric circuit. Comparing the c alculated loss with the measured one, the modeling method of the contact re sistance distribution was modified suitably. Finally the relation between t he inter-strand coupling loss and the contact resistance distribution were discussed from the viewpoint of construction of the cable. (C) 2001 Elsevie r Science Ltd. All rights reserved.