Assessment of power electronic inverter cooling requirements for a rear-axle drive

The work presented in this paper is focused on determining the cooling requirement and its effect on the reliability of a power electronic inverter used in a rear-axle drive for a hybrid car. The cooling requirements are determined through electro-thermal simulations. Several comparative electro-thermal simulations are carried out for different levels of cooling, i.e. convection coefficients, power module integration and mission profiles. The importance of taking the thermal coupling, between devices within the power module, into account is discussed. The results obtained from the electro-thermal simulations are used to estimate how the reliability is affected by the cooling requirements. Two different reliability models are used to estimate the accumulated device damage.