Model of HTS three-phase saturated core fault current limiter

A small (several hundred watts) model of a three-phase saturated core HTS f ault current limiter (FCL) was developed and tested. Iron yokes of all thre e phases were saturated by a single DC HTS coil. The coil comprised a 60 tu rns single pancake (ID 135 mm), wound after heat treatment from Bi-2223 mul tifilamentary tape in Ag matrix. The critical current of the pancake in liq uid nitrogen was 8A. The tests have shown that the limiting value of the AC current (at 50 Hz)can be easily adjusted in the range from 8A to 20A depen ding on the value of the DC current in the HTS foil. The optimum value of t he latter is 4A, corresponding to the 8 times increase of the differential resistance in the current limiting mode. The response time is very short (l ess that 1 ms). Under tests the short-circuiting event was made in one, two and all three phases. The case of short-circuiting of one phase in the thr ee-phase FCL is especially favorable from the standpoint of the voltages in duced in HTS coil compared to the one-phase FCL.