Reduction of transport current losses in Bi-Sr-Ca-Cu-O wires with transposed filaments

A new type of high temperature superconducting wire with transposed filamen ts is fabricated and tested to confirm reduction of transport current losse s. Sample wires of 1 meter long are made of four Bi2223 multifilamentary pr e-tapes which are wrapped spirally into two layers around the silver core w ire without any insulation. The wrapping direction and pitch for the two la yers can be changed easily so that both the opposite and the same direction wires are prepared for the present experiment, The sample parameters are c hosen to achieve uniform distribution of transport currents inside the oppo site-direction wire. These wires, obtained after heat treatment, have relat ively high critical currents of 95-122 amperes in liquid nitrogen in no ext ernal magnetic fields. In the range of currents higher than a half of the c ritical current, the observed hysteresis loss due to sc transport currents in the opposite-direction wire is about 60% as large as that in the same-di rection one. This experimental result for the loss reduction agrees closely with our theoretical prediction.