Thermal Analysis of Housing-Cooled Integrated Motor Drives

Integrated motor drives (IMDs) combine power electronics and motor in a single enclosure to improve power density. Conventionally, the cooling of power electronics is one of the most significant challenges of IMDs. The use of wide-bandgap (WBG) devices makes it possible to reduce the cooling system, creating opportunities to take advantage of the motor housing to cool down the power electronics. This paper develops a closed-form analytical expression that provides a fast estimate of the housing temperature profile in IMDs where the power electronics is mounted axially, in either of the machine end-bells. Radiation and convection heat transfer mechanisms are taken into account. The developed expression is compared with the results of finite element analysis (FEA) simulations. The results demonstrate that the analytical expression is quite accurate, justifying its use as guidance during early stages of the design to quickly evaluate the IMD's cooling system requirements. These results of a closed-form solution can also provide insights into the influence of various machine parameters, helping the designer to make better choices when iteratively setting up the FEA thermal simulations.