Analytical thermal modelling for permanent magnet synchronous motors

This paper concentrates on the development and analysis of a new generic steady state thermal model for mapping the heat transfer throughout a permanent magnet synchronous motor by considering its individual components as elements of an overall thermal equivalent circuit. This model includes (a) conduction resistances for the stator laminations and housing, conduction resistances between the copper winding and the stator teeth and yoke, between the housing and the stator, and between the housing and the flange, (b) heat flow in the air-gap for vortex and turbulent flow, (c) natural convection and forced cooling for the housing surface and the mounting flange surface, and (d) radiation resistance for the housing surface and mounting flange. The results obtained from the model are compared with corresponding experimental tests for the stall and rated performance with natural and forced cooling for two different motors, one with a rated speed of 1500 r/min and 130 Nm stall torque having 30 slots and 10 poles, and the other with a rated speed of 3000 r/min, and 15 Nm stall torque having 18 slots and 6 poles. The results achieved demonstrate a good correlation between the experimental results and the theoretical results obtained from the thermal model.