Characterization of Solid-State Switch Technologies for Transformer-Rectifier Flux Pumps Supplying High-Current, High-Inductance DC Magnets

Traditional power supplies for superconducting magnets suffer from significant losses mainly due to thermal dissipation through current leads. Superconducting flux pumps offer a contactless, low-voltage, high-current alternative, effectively reducing dissipation in the power supply system. They are broadly classified into traveling-wave and transformer-rectifier topologies. The latter involves a contactless AC source and a cascaded rectifier unit, usually consisting of superconducting switches driven by temperature or magnetic field, or alternative, of solid-state switches. Solid state switches provide fast switching times with nearly zero losses in the open state but produce non-zero loss during on-state, which affects overall loss performance of the flux pump during quasi-persistent mode operation. This study focuses on transformer-rectifier based on solid-state switches, emphasizing the impact of switch selection on efficiency and performance. To this aim, a characterization of the solid-state switches, both in terms of on-state resistance and switching losses, was conducted where different technologies including Si-MOSFET and GaN devices are considered. The presented characterization provides quantitative guidance for selecting solid-state switches in transformer-rectifier flux pumps supplying high-current, high-inductance superconducting magnets. These results will be used to optimize switch selection for a full-scale transformer–rectifier flux pump designed to supply a toroidal field magnet in a fusion machine, rated at 42.5 kA and 2.2 H.