Practical Estimation of HTS Dynamo Losses

Abstract

In High Temperature Superconducting (HTS) DC magnet applications, the current leads contribute a significant fraction of the cooling load. Higher current operation requires larger current leads and a larger thermal bridge into the cryogenic superconducting components. Removal of current leads into the cryogenic environment would lead to a significant reduction in cooling load and hence reduce ongoing operation costs. Superconducting dynamos are a non-contact method of energising HTS coils, capable of producing significant currents in the connected superconducting circuits that exceed usual current lead arrangements. The use of superconducting dynamos has the potential to reduce the size and mass of a complete magnet system by replacing the power source, current leads, and cryocooler. Previous work on superconducting dynamos has focused on driving larger currents, and understanding the underlying physical principles of operation, but has not investigated the AC losses associated with operation. In this work the losses of a kA class multi-stator squirrel-cage superconducting dynamo are investigated experimentally, and compared to the losses expected in the conventional copper current lead based energisation method. The thermal load associated with conduction cooled copper leads prevents practical application of kilo-amp class dc HTS magnets, however we demonstrated the feasibility of using this superconducting dynamo as an energisation method to enable feasible portable high current HTS magnet systems.