Periodic behavior of magnetic flux density in flat-type inductive fault current limiter with YBCO thin film discs during AC over-current carrying period

We focus on a flat-type inductive fault current limiter (FCL), which consists of a pancake coil and superconducting thin film discs. This paper describes an experimental and computational approach for the FCL where the primary coil is sandwiched in between two YBCO thin film discs which have different critical current each other. In this experiment, the periodic behaviors of magnetic flux density arising in the FCL were measured by pick-up coil while AC over-current injected to the primary coil of the FCL. It was found out that the magnetic flux density changes hysteretic way for injected current and the YBCO film turns into flux-flow resistive state from superconducting state at the different time. Similar result has been confirmed by the calculation using a finite element method.