Thermal analysis for design of high performance motors

Thermal analysis is very important to the design of low cost and long lifetime motors. This paper presents CFD results of air flow and heat transfer around a totally enclosed, fan cooled motor housing, which is the motor's final passage of heat rejection to ambient air. The detail geometries of finned housing, fan, shroud, inlet grill, rail supports and ground are modeled. The heat fluxes are prescribed at the inner surface of the housing. The effects of inlet grill geometry, fan rotation direction and the thermal conductivity of the housing material are examined. The inlet grill has a strong effect on fan inflow and motor temperature, whereas the rotation direction has less impact on overall temperature but results in some local variation. A good conductive ground reduces the housing temperature near the ground and an aluminium housing has a more uniform temperature distribution than cast iron. The computed temperature distributions and mass flow rate of air drawn through the motor are compared with experimental data, and they are in good agreement. The averaged convection heat transfer coefficient is obtained and can be used for future motor designs.