Frequency dependence of AC magnetization in stacked Bi-2223 Ag-sheathed tapes

Abstract

The frequency dependence of AC magnetization in stacked Bi-2223 Ag-sheathed tapes is experimentally and numerically evaluated in an external magnetic field perpendicular to their wide faces. The sample consists of 10 pieces of non-twisted Bi-2223 multifilamentary tapes, which are vertically stacked. The magnetization in the external AC field, whose frequency is varied from 1 to 60 Hz, is measured with a saddle-shaped pickup coil. The measured AC magnetization is compared not only with the theoretical curves based on the critical state model but also with the numerically calculated losses which are derived using the voltage–current characteristics represented by the n-value model, where the local electric field is proportional to the power n of local current density. Furthermore, it is shown that the eddy-current losses in a silver matrix cannot be ignored in the perpendicular-field losses at a commercial frequency.