Recovery time of Bi-2223/Ag HTS tape after quench by short-time over-current

Recovery time of Bi-2223/Ag HTS tapes after quench by short-time AC over-current has been observed. The experiment is carried out using an electromagnetic switching circuit. In order to confirm the state of the tape, a small DC current is fed continuously to the tape. The HTS tape is immersed in liquid nitrogen bath. The duration of the over-current is about 100-200 ms (5-10 cycles in 50 Hz), and the magnitude of the transient AC current is 150 A which is about 3 times larger than the DC critical current of the tape. The experimental result shows that the normal voltage generated by the over-current disappears about 2 ms after the end of the over-current. In addition to the experiment on HTS tapes, an experiment on a HTS coil wound by Bi-2223/Ag HTS tape is carried out. Also from this experiment good superconducting-to-normal-conducting recovery characteristics are confirmed. These experimental results will encourage the possibility of many applications of HTS tapes to power apparatus.