Explaining the self-field AC loss behaviour of silver-clad (Bi,Pb)-2223 tapes for power engineering applications

The AC losses of mono- and multi-filamentary (Bi,Pb)-2223 silver-sheathed tapes due to an applied AC current have been measured. The data are compared to the Norris equations for the AC loss of elliptical and thin-strip superconductors. Reasons for the observed differences between theory and measurement for these tapes and others in the literature are discussed. It is suggested that the main factors determining the self-field AC loss in such practical superconductors are the transverse J(c) distribution in monofilaments and the filament distribution in multifilamentary tapes. For the latter, evidence is provided that tapes with filaments arranged in columns have a lower loss. For the development of low loss conductors for power applications these factors need to be accurately controlled over long lengths, requiring much improvement to existing processing techniques. (C) 1997 Elsevier Science B.V.