AC transport losses of Ag-sheathed Bi2223 multifilamentary twisted tapes

Abstract

The ac transport losses are investigated at 77 K on the Ag-sheathed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/, multifilamentary twisted tapes with filament number N=19 and twist length of 13 mm, through an ac transport method under self-fields. The losses for the twisted tapes are independent of the frequency, so that the main contribution to the losses are the hysteresis loss in the superconductor filaments. The absolute values of the losses agree with the results of Norris theory for an elliptical superconductor with the same critical current. In addition, the resistive voltages on the twisted tapes have a dependence on the potential-taps configurations, which is found in the monofilamentary tape and multifilamentary untwisted tapes. Furthermore, the wave-forms of axial electric fields are similar to the theoretical results for a superconducting cylinder. These results suggest that the distribution of the transport current in the superconductor filaments is not equalized for the twisted tapes and the twisting of filaments causes no notable influence on the at transport properties when the tapes are examined in self-fields.