Test and simulation of a textured YBCO superconductor for high current fuse

摘要

A textured YBCO superconductor (high temperature superconductor, HTS) measuring 18 x 2.5 x 0.3 cm has been tested above the critical current in order to characterise it for high current application as a fuse element. The HTS had a I_c of ≈585 A (77 K) and was tested with (a) an asymmetric AC peak current, I_(max), of 2.5 kA falling to 1.6 kA where the HTS survived an over current of 4I_c, and (b) an asymmetric I_(max) of 5.2 kA decreasing to 3 kA where the HTS heats up, quench and break after 80 ms. The rupture is followed by a periodic arc that dies out after 1.5 period as the current is passed through a shunt. In order to act as an efficient current limiting device the fuse should become normal conducting within 5 ms and this can only be obtained by a fault current of more than 8I_c. Calculations indicate that with a current of 16 kA_(rms)/cm~2 or 23 kA_(peak)/cm~2 the HTS element would melt within this time interval, but the HTS element would presumably break at lower current due to the formation of a hot spot.