Chapter 114 - AC loss characteristics of Bi-2212 multifilamentary round wires and their cables

Abstract

This chapter describes AC loss properties of Bi-2212 multifilamentary round wires and their Rutherford-type cables, which may be one of candidates for large-capacity windings in the electrical devices such as future superconducting magnetic energy storages (SMES) and so on, from a viewpoint of feasibility study. The strands are not twisted. Their AC loss properties in a transverse magnetic field are to be like those of monofilamentary wires in spite of the multifilamentary structure. The experimental results partially support the prediction that the AC loss is hysteretic. The experiments also give unexpected results that the effective diameters of the filamentary region evaluated from the measured AC losses are much smaller than the actual ones. The AC losses obtained for the strands were scarcely dependent upon the frequency of the external field in the range from 0.02 Hz to 10 Hz. This suggests that the hysteresis loss in a tightly coupled filament bundle be dominant. A remarkable improvement in the AC loss characteristic by reducing an effective diameter of the filament bundle are observed, while twisting the filaments itself does not contribute to the reduction in the AC loss. It is also found from the comparison between the AC losses in the strands and the cables that the AC losses in the cables mainly came from the individual strands.