HYBRID SUPERCONDUCTING AC FAULT CURRENT LIMITER PRINCIPLE AND PREVIOUS STUDIES

One of the most promising uses of the low a.c. loss ultra fine wires in electrical devices is the fault a.c. current limiter. The superconducting a.c. current limiters may be separated in two kinds: the resistive and the inductive one. For the resistive limiter the superconducting winding triggers and assumes the limitation. For the inductive one the superconducting winding plays only as trigger while the fault current is limited by another winding superconducting or normal. In this case it may be hoped a limited heating of the superconducting coil and then a very short recovery time. It will enable to quickly restore the service. On the other hand the current in the trigger coil may be chosen lower than the rated current so that the choice of the superconducting wire may be easier. The use of a judicious magnetic circuit increases the performances of the inductive current limiter as it decreases the voltage drop in rated operation and the heating of the superconducting coil during fault.