Influence of tape's critical currents and current distributions on AC loss measurement in a multi-tape conductor

AC loss is an important issue to design high temperature superconductor power cables, which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have intrinsically different critical currents, and they are electrically connected to each other and current leads. This makes loss measurements considerably complex, especially for short samples. In this work, we have prepared a multi-tape conductor composed of Bi-2223 tapes. The ac losses of the conductor have been experimentally investigated. The loss tests indicate that the effect of critical currents of each tape on AC loss measurement in the multi-tape conductor is negligible only if currents in the tapes flow uniformly. Moreover, the measured loss of the conductor is in good agreement with the sum of the transport loss in each tape. However, in the case of nonuniform current distribution, the measured AC loss considerably depends on the current distribution parameter /spl gamma/, and the positioning of a voltage lead. Thus it should be very careful to measure the AC losses in the short power cable samples.