Quench Protection of Bi-2223/Ag Tape Using SFCL Made of YBCO Thin Film

As a fundamental study for the safe operation of high temperature superconducting (HTS) machines, AC over-current characteristics of HTS tapes and the method for the protection using superconducting fault current limiters (SFCLs) were investigated. Firstly, the AC over-current characteristics of a Bi-2223/Ag tape were investigated. Various amounts of AC over-currents were applied and the quench behavior was analysed, measuring resistance increase with applying time. Secondly, based on the over-current characteristics of the HTS tapes, SFCLs made of YBCO thin films was applied to the protection of the HTS tapes for the safe operation. At this time, the quench characteristics of the HTS tape and the SFCL were considered simultaneously and each electrical operation was compared. At the transition range from super- to normal state in the HTS tape, quench behavior of both materials was investigated in detail. From the experiments, the safe operation state of HTS tapes was achieved and the optimal design factors for the SFCL applications were acquired.