Transient Thermal Analysis of Epoxy-Impregnated Superconducting Windings in Linearly Ramped Fields

Heat is generated in superconducting windings whenever the magnetic field changes. During these transient periods, the current carrying capability of the superconductor is limited by the temperature distribution inside the winding, especially in epoxy-impregnated winding composites that have limited thermal conductance. A finite-difference transient thermal analysis of a superconducting winding composite is presented. The analysis is employed to predict the critical current of a cylindrical coil and a modular racetrack winding under linear ramping of the magnetic field, when eddy current losses and hysteresis losses prevail. The dependence of these losses on the magnetic field and temperature is properly accounted for. The analytical predictions are compared to experimental data and the agreement is excellent.