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

Abstract

Transport ac losses in multifilamentary (Bi,Pb)SrCaCuO-2223/Ag tapes with different filament arrangements have been measured. The samples were untwisted and had seven filaments, which were arranged in columns, in slanted columns, or evenly distributed across the tape cross-section. The aspect ratio of the samples as well as their filamentary regions was the same. Special care during processing ensured that the filaments had the same orientation or arrangement along the sample length and that filament bridging was avoided. The ac losses were measured in the frequency range 40 Hz–120 Hz. Two different methods of determining the critical current were used: from dc current–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 rectangular cross-section of similar aspect-ratio. It was found that the sample with filaments stacked in columns had slightly lower normalized losses at low normalized currents ( I o/ I c<0.2) compared with other filament arrangements. 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 tapes containing bridged filaments, but having similar critical currents, had variable normalized ac loss.