Investigation of Thermal Distribution in Cryogenically Cooled Inverter for HTS Motor

In superconducting electric propulsion systems, power inverters must operate reliably under cryogenic environments to efficiently drive superconducting motors. Integrating power electronic inverters within the existing cryogenic cooling system for superconducting motor can simplify cooling circuits and enhance system-level compactness. Moreover, the on-state and switching losses of insulated gate bipolar transistor (IGBT) reduce at cryogenic temperature, thereby improving efficiency. Previous studies have shown that the characteristics of power devices are highly dependent on temperature. However, limited research has investigated how inverter design parameters affect thermal distribution when the inverter is directly coupled with a cryogenically cooled superconducting drive system. This paper experimentally investigates both output and switching characteristics to examine the changes in IGBT losses under different temperatures. A comprehensive analysis is given on how design parameters influence thermal distribution in cryogenically cooled inverters with rated power of 100 kW. The results provide practical guidelines for thermal design and integration of power electronics in superconducting propulsion systems.