Electrical behavior of Bi-2223/Ag tapes under applied alternating over-currents

As a study for the protection of HTS power machines operated under AC conditions, the electrical behavior of Bi-2223/Ag tapes with applied alternating over-currents was investigated. Using the HTS tape of 57 A I_c and 106 K T_c, we measured the V-I curves for the over-critical current region from 150 A_p to 507 A_p. From the experimental results, 3 matters were investigated. Firstly, using the resistance increase data obtained from the curves, quench development was analyzed as a function of the amplitude and duration of the applied currents. Secondly, to understand these phenomena in detail, we investigated the current distribution between the superconductor and the metal sheath in Bi-2223/Ag tape, applying the equivalent equations and data of V-I curves. Finally, we confirmed the relationship between the resistance and temperature generated by the over-critical current experimentally. As a result, we could find the optimal operating condition considering the protection of the HTS tape against the alternating over-current.