Two-Phase Immersion Cooler for Medium-Voltage Silicon Carbide MOSFETs

Medium-voltage (MV) silicon carbide (SiC) MOSFETs play a pivotal role in various industrial applications, including electrical vehicles, DC fast charging stations, and renewable energy conversion systems, among others. Compared to their silicon counterparts, the MV SiC MOSFETs feature higher efficiency, faster switching speeds, lower heat generation, and higher power density. Despite their advantages, SiC MOSFETs also lead to higher cooling demands. To address this challenge, we have developed a two-phase immersion cooler, in which the base plate is immersed in the liquid pool, and vapor generated from coolant boiling on the base plate is condensed on the top surface of the immersion cooler under external air cooling. To further improve the cooling capacity, the base plates are textured with microchannels. Experimental tests have been performed to characterize the thermal performance of the two-phase immersion cooler with a state-of-the-art 6.5kV SiC device. The immersion cooler with microchannels exhibits decreasing thermal resistance with the power load and is shown to be superior to conventional air-cooled heat sinks when the power loads are beyond 70 W. Leveraging the feature of reduced thermal resistance with the power load, the fan power can be tuned based on the power load to increase the lifetime of the fans.