Fault Current Limiting Properties of ${\rm MgB}_{2}$ Superconducting Wires

Abstract

We have investigated magnesium diboride wires as an element in a resistive superconducting fault current limiter using a pulsed system, which could deliver a fixed number of AC cycles to avoid burnout due to thermal instabilities. Experiments have been carried out in both liquid helium and at 27 K on magnesium diboride mono-core wires in stainless steel tubes, in a CuNi sheath with an Fe barrier and also on multifilamentary wires with Nb barriers. Experiments showed good current limiting in the first cycle and no damage after six cycles. Also wires with a number of voltage contacts spaced at about 1 cm intervals to assess the effect of inhomogeneity were tested. Relatively small differences in local J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> led to large differences in the local temperature rise although in no case did this lead to failure of the conductor. The results were compared with those on Bi-2223/Ag tapes and YBCO coated conductors measured in liquid nitrogen.