Fast Current Regulation and Persistent Current Maintenance of High-Temperature Superconducting Magnets With Contact Power Supply and Flux Pump

Due to the properties of high-temperature superconducting (HTS) materials, current attenuation is inevitable during the closed-loop operation of HTS magnets. When a contact dc power supply is used to supplement this attenuation, it inevitably creates a huge thermal burden on the cryogenic system. The flux pump is a revolutionary new power source that can charge closed-loop HTS magnet wirelessly. However, for HTS magnets with a large inductance, the flux pump cannot fast adjust the dc current of the magnet due to its small dc output voltage. Here, we present a method to fast regulate the current in a closed-loop HTS magnet using a contact dc power supply and persistent current switch. After current regulation, the HTS magnet is operated in the persistent current mode with a flux pump. Applying the "four-quadrant" control theory of the flux pump allows the current in the HTS magnet to be controlled with high stability. The study provides a power strategy for the fast current regulation and maintenance of persistent current in the HTS magnet, enabling the industrial applications of flux pumps for HTS magnets with large inductance.