抄録
The characteristics of a multi-layered conductor, which was an assembly of Bi-2223 Ag-sheathed superconducting wires, were investigated. We confirmed that experimental value of the self-field loss in the multi-layer conductor was nearly identical with a theoretical value based on a critical-state model. In detail, the experimental result was well explained by the power law model assuming that the current-voltage characteristic of the high-Tc superconductor is well approximated as V∝In. We also investigated the AC current distribution of each superconducting layer using 50m/4-layer conductor. As measured with a Rogowski coil, it was found that an unbalanced current distribution occurred in the multi-layer conductor. It is possible to reduce the AC loss by suppressing unbalanced current distribution. As a solution, we suggested to adjust the pitch of the conductor in order to equalize the impedance of all the layers. For this we estimated the condition for a balanced AC current to each layer by calculation.
