DC critical current estimate of the short HTS cable consisted of Bi-2223 tapes

The 4-probe method with a voltage tap on terminals has been used for the measurement of the critical current of multi-strand high-T_c superconducting (HTS) cables. The critical current of cables is obtained as the measured total current divided by the number of conductors when the terminal voltage exceeds the predetermined criterion of critical current. However, because of the nonuniform current share due to the different critical currents, shapes, and other characteristics of each conductor, this method is not applicable to the multi-strand HTS cable. To determine the critical current of multi-strand HTS cable, the critical current of each conductor must be measured with different method. In this paper, the current share and the critical current of each conductor in multi-strand cable were measured with specially made pick-up coils and voltage taps. It is presented that the real critical current of multi-strand is smaller than sum of each critical current of each path. Different resistances appeared in each HTS wire are the main cause of nonuniform current share.