AC losses of Ag-sheathed (Bi, Pb) 2Sr 2Ca 2Cu 3O x monofilamentary and multifilamentary tapes

Abstract

The AC losses are investigated at 77 K on the Ag-sheathed (Bi, Pb) 2Sr 2Ca 2Cu 3O x monofilamentary tape and multifilamentary tapes with filament numbers equal to 7, 19, 37 and 61, through an AC transport method under self-fields and an AC magnetic method under longitudinal fields. Although the main contribution to the AC losses around a commercial frequency of 50 Hz comes from the hysteresis loss independent of the measuring methods, the AC transport losses for the monofilamentary tape are larger than the AC magnetic losses by about one order of magnitude. Such a discrepancy is explained by a large aspect ratio of the superconductor core, which lowers only the magnetic losses. The superconductor subdivision in the multifilamentary tapes causes no notable influence on the AC transport losses ascribed to the hysteresis loss. This is compared with the result for the AC magnetic losses that the subdivision suppresses the contribution of the hysteresis loss while enhancing that of the eddy current loss. The density distribution of the AC transport losses obtained from numerical calculations based on a critical state model shows a resemblance between the monofilamentary tape and the multifilamentary tapes, which conforms to the experimental results for the AC transport losses.