Electromagnetic properties in parallel conductors composed of Bi2223 multifilamentary wires for power transformer windings

The authors study, theoretically, the AC losses in superconducting parallel conductors exposed to a transverse alternating magnetic field in relation with transposition among the strands. They obtained an analytical expression of the additional coupling loss for the deviation of transposition from an optimum condition. The AC losses for the alternating external field were measured in parallel conductors composed of Bi2223 and NbTi multifilamentary wires. The additional losses can be well explained by the theoretical expression in a wide range of the amplitude of external field. They also estimated, experimentally, the current distribution among the strands in solenoidal coil of the parallel conductor and discussed the effect of transposition on the current distribution.