Thermal stability analysis of high temperature superconducting magnet coils under overcurrent pulses

This paper presents some numerical simulation results of thermal behavior on the high temperature superconducting (HTS) magnet coils wounded by Bi2223/Ag multifilamentary tapes subjected to an overcurrent pulse using the finite element method (FEM). The analytical results show that the time-varying spatial temperature distribution of the HTS magnet coils under the condition of different overcurrent pulses has an important influence on its stability estimation, and the temperature dependence of minimum propagation current plays a key role in the stability analysis of the HTS magnet. Through the FEM analysis, the permitted duration time of 5-multiple overcurrent pulse has been obtained for the HTS magnet under the various operating conditions and cooling conditions. In this paper, an analytical method for determining the stability of the HTS magnet coils subjected to an overcurrent pulse has been proposed and a stability criterion has been presented. The critical current and minimum propagation current can be chosen as the restrictive condition of operating current in the HTS magnet coils subjected to an overcurrent pulse.