AC Transport Loss of Coated Conductors in Anti-Parallel Arrangement

AC loss in two stacked coated conductors (CC) carrying opposite currents was investigated by experiments and numerical simulations. This arrangement is a promising option in the design of fault current limiter (FCL) because the transport current loss could be significantly lower than in the self-field configuration of one single tape. The requirements of normal-state resistance indicate that in the particular CC tape developed for FCL application the metallic stabilizing layer should be less than ~10 μm. Considering the electric strength of up-to-date insulations this leads to ~100 μm distance between superconducting layers. Our study shows how sensitively depends the loss on this quantity. Even in the case of coated conductors prepared on ferromagnetic substrate a substantial reduction of the substrate loss can be achieved by putting the tapes in close proximity with superconducting layers facing each other from minimum distance. Another factor influencing the AC loss is the variation of critical current density across the tape width. Then the comparison of calculated and measured loss data allows to assess the tape quality in a non-destructive way.