Current Distribution Measurement of YBCO Thin Film for Superconducting Fault Current Limiter

Current distribution in the superconducting film for a resistive fault current limiter is important because it influences AC loss and a uniformity of S/N transition. The lateral current distribution of the film was reconstructed from the magnetic field distribution, which is measured by multiple Hall probes. The following results were obtained. (1) Non-uniform current distribution in the superconducting film was observed when the current was less than 1.3times critical current (Ic). (2) The current in a superconducting film was uniform when the current was much higher than Ic. The current can be considered uniform when the film works as a fault current limiter because the S/N transition starts at about twice Ic. (3) The validity of the measurement was verified by the comparison with the electric circuit simulation.