HTS coil with enhanced thermal stability in over-current operation for fast response magnet power application

This paper examines the effect of improved winding geometry on high-temperature superconducting (HTS) coils for use in superconducting power applications. One of the most important functions in such a superconducting magnetic energy storage system is to charge-discharge the superconducting coils as fast as possible to secure sufficient power demand. The HTS coils are vulnerable to the thermal instability caused by cyclic and/or unexpected charge-discharge variation. Therefore, it is necessary to enhance the safety of the HTS coils under fast response operation at the request of varying loads. In this study, improved thermal stability in over-current operation is demonstrated by implementing the proposed insulation scheme. The performance of the HTS coil with the proposed winding geometry was experimentally evaluated in comparison with a conventional insulation (CI) coil. Cryo-stability characteristics of the proposed coil are verified with a circuit analysis under a charge-discharge operation scenario. The results of this study show the usefulness of the proposed winding coil as a replacement for CI coils, which have drawbacks related to thermal recovery rate in over-current operation.