Thermal Management and Sensitivity Study of Air Cooled SMPM Motor

High temperatures in the surface mounted permanent magnet (SMPM) synchronous motor adversely affect the power output at the motor shaft. Temperature rise may lead to winding insulation failure, permanent demagnetization of magnets and encoder electronics failure. Prediction and management of temperatures at different locations in the motor should be done right at the design stage to avoid such failures in the motor. The present work is focused on the creation of Lumped Parameter Thermal Network (LPTN) and CFD models of SMPM synchronous motor to predict the temperature distribution in the motor parts. LPTN models were created in Motor-CAD and Simulink which are suitable for parameter sensitivity analysis and getting quick results. Air is assumed to be a cooling medium to extract heat from the outer surface of motor. CFD models were useful in providing elaborate temperature distribution and also locating the hot-spots. Correlation models by both the methods, viz. LPTN and CFD, were generated. The effect of changing the motor orientation, magnitude of air inlet velocity, direction of air-flow and the effect of axial fins on motor housing, on the temperature of motor parts was investigated using the correlated CFD model. The increase in inlet velocity and provision of axial fins substantially improves the cooling. Further, the sensitivity analysis was done considering a perfect fit between the motor parts and then increasing the interface gap values. It is noticed that with increase in the interface gap between stator lamination and housing the winding hotspots are developed.