AC Losses in (Bi, Pb)2Sr2Ca2Cu3Ox Silver-Sheathed Superconducting Wires

In this study, ac losses in BSCCO silver-sheathed wires, both single- and multi-filamentary, were investigated by means of ac-magnetization and ac-transport techniques. It was shown that the longitudinal magnetization ac loss in a single-filamentary wire could be quantitatively explained by the simple sum of the magnetic hysteresis loss of the superconducting core and the eddy current loss in the silver-sheath, while those in multi-filamentary wires behaved quite differently, possibly being affected by electromagnetic coupling between filaments. On the other hand, the self-field ac loss of all the wires employed was found to be well described by a simple expression derived for a uniform superconducting cylinder based on Bean's model. Namely, the self-field ac loss was determined solely by Ic and Ip/Ic (Ip: peak value of the transport current), regardless of their cross-sectional structure, and the distribution of the current flow is considered to have an elliptical symmetry even for multi-filamentary wires, where the critical state is established from the outermost filaments toward those in the interior. It is suggested that the self-field loss of multi-filamentary wires can be reduced if the distribution of the current flow can be made equivalent for all filaments.