Abstract
A high-temperature superconductor is investigated to be applied to a fault current limiter. However, a current carrying capacity of a single element is too low for a practical use. So parallel connection of superconducting elements is required to increase the current capacity. This paper discusses an a. c. current distribution between two YBa2Cu3O7-x superconducting elements connected in parallel that differ in electrical aspects such as a critical current level and voltage-current characteristic. As the instantaneous value of the current rises from zero to peak, the following processes are observed: (1)The transition from superconducting to normal conducting state is initiated in the element with the smaller critical current. (2) The current value in the element is kept constant until the other element with the larger critical current level becomes normal conducting state. (3) Only when the instantaneous value of the a. c. current exceeds the summation of the individual critical current values of each element, the voltage across parallel-connected elements appears. These results are caused by quick recovery characteristic of our YBCO superconductors from normal conducting state to superconducting state.
