Transport ac losses in (Bi,Pb)SrCaCuO-2223/Ag multifilamentary tapes with different filament arrangements

Transport ac losses in multifilamentary (Bi,Pb)SrCaCuO-2223/Ag tapes with d ifferent filament arrangements have been measured. The samples were untwist ed and had seven filaments, which were arranged in columns, in slanted colu mns, or evenly distributed across the tape cross-section. The aspect ratio of the samples as well as their filamentary regions was the same. Special c are during processing ensured that the filaments had the same orientation o r arrangement along the sample length and that filament bridging was avoide d. The ac losses were measured in the frequency range 40 Hz-120 Hz. Two dif ferent methods of determining the critical current were used: from de curre nt-voltage characteristics and from the saturation value of ac losses. The experimental results were compared with theoretical models. The normalized ac losses approximately follow the theoretical dependence of a tape with re ctangular cross-section of similar aspect-ratio. It was found that the samp le with filaments stacked in columns had slightly lower normalized losses a t low normalized currents (I-o/I-c < 0.2) compared with other filament arra ngements. There was no difference in the loss data for the three different filament geometries in the range I-o/I-c > 0.2. It was also observed that t apes containing bridged filaments, but having similar critical currents, ha d variable normalized ac loss. (C) 1999 Elsevier Science B.V. All rights re served.