Liquid Metal Magnetohydrodynamic Pump for Junction Temperature Control of Power Modules

Power modules are the most common components to fail in power converters that are employed in mass transportation systems, thus leading to high unscheduled maintenance cost. While operating, high junction temperature swings occur that result in high thermomechanical stress within the structure of the power module reducing the lifetime of the module. Liquid metals as a cooling medium received so far little attention in the area of power semiconductors cooling, despite being able to remove high heat fluxes. This paper shows for the first time how liquid metal is used to reduce actively the junction temperature swing. A magnetohydrodynamic (MHD) pump has been designed for this purpose allowing active control of the flow rate of the liquid metal that impinges against the baseplate of the module. The pump has been 3D printed and forms with the power module a unique unit. A closed-loop temperature control system is implemented, able to estimate the IGBT's junction temperature and thus, control the MHD power. The paper presents simulation and experimental results showing reductions in the temperature swing over the full load cycle with 12oC as the highest observed reduction rate. The paper shows also detailed designs of the MHD pump and the controller hardware.