Model-Based Comparison of Thermo-Hydraulic Performance of Various Cooling Methods for Power Electronics of Electric Vehicles

This paper presents a thermo-hydraulic comparison of common and less commonly used cooling methods for power electronics used in electric vehicles, based on models available from literature. The current increase in power density of electric motors requires a higher power delivered by the electronics resulting in a higher heat dissipation. To achieve this, an appropriate method should be selected to cool the junction below the maximum operating temperature. A lot of information about commonly used and more advanced cooling methods is available in literature, but it is difficult to compare these methods for a specific application since the performance is determined starting from different boundary conditions and geometries. However, a comparison of the thermal performance based on the total thermal resistance from coolant to junction, is the starting point when selecting the possible cooling methods. In this paper a comparison is made between the different methods starting from the same conditions, to determine whether the maximum junction temperature can be respected by these methods. For each of the possible cooling methods, a suitable model is selected based on a literature study, which is used to predict the thermal performance. These models are combined with the thermal model of an inverter used in the automotive industry, to predict the junction temperature for a certain flow rate and corresponding pressure drop and pumping power. The obtained results about the thermal performance of the different methods can be used to select the most adequate cooling method by taking into account other criteria (cost, complexity,…). These other criteria such as feasibility and total cost of ownership, are however not studied in this paper. The proposed approach and model-based comparison of this work result in an optimized choice of cooling method and a more performant cooling design.