800 V Traction Inverter Power Stage with Double-Side, Direct-Liquid-Cooled Phase-Leg Modulets

Abstract

For SiC-based traction inverters, advanced device packaging and cooling are key improving power density and reducing costs. This thesis describes the design, simulation, fabrication, and testing of a power stage for 800 V traction inverters, utilizing 6 1.2 kV, 139 A SiC MOSFETS. The design comprises three double-side cooled phase-leg modulets integrated into a direct liquid cooling jacket, with sintered silver acting both as a die attach material and as DSC interposers in the modulets. Steady-state thermal simulations were used to estimate a modulet junction-case thermal resistance of 0.17 ℃/W. Parasitic extraction simulations showed a parasitic induction of 7.19 nH from the DC+ to DC- terminals of the modulet. Full conjugate heat transfer simulations performed on the full system to inform design parameters and estimate junction-water thermal resistance. A prototype of the modulets and cooling system were fabricated and assembled for experiments on a custom-built performance test bench. Fluid and thermal characteristics were determined both in absolute and area-normalized terms, with a specific junction-coolant thermal resistance of 22.3 (℃∙〖cm〗^2)/W at 20.7 mW/〖cm〗^2 of pumping power. A volumetric power density for the power stage was estimated at 273 kW/L. Simulated and experimental results were compared and analyzed, and areas for performance improvement were identified.