An integrated approach to developing thermal models for automotive electric drives

Numerical simulations of heat transfer in an electronic control unit (ECU) for an automotive application are developed in Ansys (R) Icepak (TM). The approach described in this paper sets a framework that allows a comprehensive and integrated thermal analysis of the ECU under varying loading conditions. The approach lends itself to operating point characterization, design optimization, development of reduced order models and subsequent integration with system models. This is desirable since it saves substantial costs associated with sizing of ECUs, power components and development of test setups for iterative design development. Further, the adequacy of PCB (printed circuit board) traces for transient loads is verified in this work which is very valuable for cost savings and product reliability. Experimental validations are performed to support the analysis with constant and varying power losses through the components. The results obtained from the simulations compare very well, within 5% of the results obtained from experiments. The integrated thermal models developed herein provide an accurate estimation of MOSFET junction temperatures which is crucial for power electronics design.