Quench characteristics of HTS tapes with alternating currents above their critical currents

In this study, the dependence of quench characteristics of HTS tapes on the amplitude of current and duration time was investigated by applying alternating current (AC) that is several times over the critical currents of HTS tapes. When the applied AC/sub peak/ was up to three times of critical current, the joule heat was not cooled down by LN/sub 2/ completely. However, when the over-current reached four times of critical current, the superconducting region began to decrease gradually and the total resistance of HTS tapes increased rapidly. Finally, we analyzed the quench development using voltage-current characteristics and examined the influence of pitch angles on resistance increase.