High-power-density fault-current limiting devices using superconducting YBa2Cu3O7 films and high-resistivity alloy shunt layers

Switching of superconducting thin-film resistive fault-current limiting devices with alloy shunt layers was studied. Au–Ag alloy thin films, whose room-temperature resistivity is about six times higher than that of pure gold, were sputter deposited on YBa2Cu3O7 films on sapphire substrates with high critical current density of Jc=3.05±0.05MA∕cm2. A small sample, 5mm wide and 40mm long, had the capacity of a rated current of 32Arms in normal operation and withstood a high voltage of 107Vrms for 0.1s after switching, resulting in a very high switching power density of ∼1.7kVA∕cm2, which is more than four times higher than conventional devices using gold shunt layers.