This study investigates a 3D numerical analysis of the thermal behavior of a permanent magnet (PM) motor, performed by Finite Element Method (FEM) by using open source Feel++ software. In the developed FEM model, the windings and the stator are treated as homogeneous medium with equivalent thermal parameters and the effective properties to characterize the thermal behaviour are calculated based on the volume-weighted average over all constituents. In order to check the accuracy of the computed temperatures, experimental tests were performed in the transient-state. The thermal analyses based on the numerical method are compared with the measured results taken from the prototype machine.