On stability of multistrand cables with insulated or highly resistive matrix strands

摘要

The stability of multi-strand superconducting cables or cables-in-conduit is degraded by rapid changes in current or field (ramp rate limitation or current degradation). The maximum achievable AC current is significantly less then the sum of DC critical currents of strands. Measurements of the dependence of quench current on ramp rate were made for one, two, and three strand cables. Samples had different strand types and lengths. It was shown that although the theory of thermomagnetic instability explains single strand performance very well, it does not explain the reduction of quench current observed in multi-strand cables. The influence of joint resistance between cable strands and current leads is shown to be the most probable reason for the reduction.