Influence of ferromagnetic slice on the charging performance of a through-wall HTS flux pump employing a magnetic coupler

High-temperature superconducting (HTS) magnets have been investigated widely for their higher upper critical magnetic field, larger engineering critical current density and simpler cryogenic system compared with low-temperature superconducting magnets. However, in order to keep the permanent-current mode of the HTS magnets, the external power supply is usually employed to charge the magnet via copper current leads, which is a considerable heat source to the cooling system. Thus, in order to avoid the heat disturbance brought by the current leads, a new 'through-wall' dynamo-type HTS flux pump using a pair of magnetic couplers is proposed, realizing the truly wireless power transfer, and exploring its possible application for the conduction cooled system. Based on the proposed structure, the heat conduction, which was calculated to be about 7.75 W, and heat convection could be minimized. In addition, to further improve the charging performance of the dynamo-type flux pump, a ferromagnetic (FM) slice was added at different positions of the system. The effect of the FM slice on charging performance is studied numerically and experimentally. According to the results of simulations and experiments, adding an FM slice under the HTS stator improves the saturated current and the charging speed of the dynamo-type flux pump by 20%-30%.