Safety consequences of shorted turns in a cryostable superconducting magnet

Abstract

A combined thermal and electromagnetic analysis has been carried out for a shorted turn in a cryostable superconducting magnet during charging or discharging. Three analyses are reported. In the first, the Joule heat generated in the short and the shorted turn is assumed to heat the turn to a temperature from which that heat will be transferred to the liquid helium coolant. The reduction in heat due to the enthalpy change of the conductor is ignored. The second incorporates enthalpy change of the conductor and heat transfer to the liquid helium. The turn temperature is determined from a heat balance, including the specific heats of all material in the conductor. The effect of current sharing is included. For the third, the electromagnetic analysis has been incorporated into a quench and safety analysis program to provide for current division between the shorted turn and the short and for heat generation at the short. The three analyses have been applied to the superconducting magnet under construction at Argonne National Laboratory for MHD research at the Coal Fired Flow Facility. The analyses predict that for the values that could be expected for short resistance and discharge time, a shorted turn would not lead to high temperature or other serious consequences.