Critical current capacity of superconductors at different AC frequencies

The measurement of quench currents of sample coils at frequencies from 0 to 1000 Hz in an external magnetic field are presented. Coils were wound with multifilamentary Nb-Ti wires with various diameters in pure high-resistivity matrices with different resistivities. The influence of cooling on quench in the AC mode was studied. The stability of the wire increased with improved cooling and increased magnetic field. Results were analyzed from the point of view of the theory of stability, which takes into account real voltage-current characteristics of the wires.