Critical state and AC losses in multifilamentary BiSrCaCuO-2223/Ag tapes studied by transport and magnetic measurements

AC losses in two multifilamentary BiSrCaCuO-2223/Ag tapes differing in number of filaments were determined by transport and magnetic measurements. In the latter, the AC field was directed perpendicularly to the wide side of the tape and the model of a superconducting strip was used in the calculations, Comparison of the experimental data with theoretical models confirmed that when the tape carries a transport AC current, strong electromagnetic coupling between filaments leads to non-uniform distribution of current among the individual filaments, On the contrary, the results of magnetic measurements were consistently explained only if we supposed a negligible electromagnetic coupling between filaments, This effect could explain the commonly observed discrepancy between AC transport and magnetic loss measurements. By taking this effect into account, the apparent lack of consistency in the J(c) value of the superconductor derived from transport and magnetic experiments disappears. (C) 1997 Elsevier Science B.V.