The effect of electromagnetic and mechanical stresses on critical current of Nb/sub 3/Sn cable developed for superconducting generator

Abstract

A Nb/sub 3/Sn superconducting cable for use as the field winding conductor of a superconducting generator was developed with the in-situ process. A magnetic field of up to 7 T, and a transverse compressive mechanical force of up to 29.4 MPa were applied to the conductor, and the critical current and strain of the cable were measured. A cyclic compressive mechanical force was also applied in order to simulate DSS operation of the generator for up to 30 years. Over 10,000 loading cycles, the critical current showed no degradation and was constant. By changing the magnetic field direction while maintaining the current direction, both compressive and tensile electromagnetic stresses were applied to the cable, and the critical currents were measured under both conditions. The critical current under compressive stress was smaller than that under tensile stress. Thus, it became apparent that electromagnetic strain must be considered when measuring the critical current of large current capacity Nb/sub 3/Sn superconducting cables.