Abstract
High Temperature Superconducting HTS current lead has been prepared by the TFA-MOD processed YBCO tapes. The YBCO tape has higher critical current density Jc and better magnetic property than the Bi2223 tape. Furthermore, thermal conductivity of YBCO tape with thin Ag layer is much lower than that of Ag-sheathed Bi2223 tape. The critical current of the YBCO tapes ranges from 150 A to 190 A in liquid nitrogen and self-field. A current lead is composed of eight YBCO tapes, Cu end caps and a pair of stainless steel boards. Rogowski coils and Hall sensors used for estimation of current distribution are attached on each YBCO tapes. The transport current of 1000 A was carried with no voltage on every YBCO tape at 77 K. The voltages between Cu cap and YBCO tapes almost linearly increased with increasing transport current, and they range from 0.206 mV to 0.234 mV and 0.210 mV to 0.230 mV at 1000 A, respectively. The low voltages correspond to 0.206 μΩ to 0.234 μΩ and 0.210 μΩ to 0.230 μΩ. The low contact resistance results in low joule heating at Cu joints. The current calculated by Rogowski coils in eight YBCO tapes varies from 4 A to 179 A at 1000 A and sweep rate of 200 A/s. Therefore, the imbalance among eight YBCO tapes is evaluated to be 175 A. The current of eight YBCO tapes calculated by Rogowski coils sums up to 1001 A, which is the slight difference of 1 A in comparison with transport current of 1000 A. Rogowski coils and Hall sensors are effective at evaluating of current distribution for current lead.
