Thermal analysis of permanent-magnet synchronous reluctance machines

This paper presents a thermal analysis of permanent-magnet synchronous reluctance machines (PM-SRM). Particular focus is put on the rotor and two lumped parameter (LP) thermal models of the rotor are implemented and evaluated. The results of the two LP thermal models are compared to thermal simulations using the finite element method (FEM). Induced eddy current losses in the permanent magnets are computed using three-dimensional (3D) FEM computations whereas the losses in the electrical steel are obtained using a 2D FEM model. Based on type of cooling system, two cases are evaluated and the agreement between the two LP thermal simulations and the thermal FEM simulation is generally good but particular differences are highlighted. In the first case, the water cooling system manages to effectively handle the dominating copper losses which results in only a minor temperature difference between the shaft and the inner part of the stator teeth. In the second case, it is assumed that there is a significant temperature difference between the rotor shaft and the stator.