Torque components in integral- and fractional-slot IPM machines

The anisotropic interior permanent magnet (IPM) synchronous machine is characterized by two torque components: the PM torque and the reluctance torque. The aim of this paper is to investigate the torque components of such a machine. Both integral- and fractional-slot windings are analyzed. To this aim different machine geometries, e.g slot and pole combinations, are considered. The impact of stator winding and rotor poles on the torque mechanism is evaluated, focusing on the correlation of the rotor geometry and the preponderance of one of the two torque terms. The results confirm that the rotor anisotropy play a fundamental rule on the machine features. Then is has to be to maximized since the reluctance torque is still present and relevant even if a fractional-slot wingding is adopted. In addition, the two torque components are analyzed when the machine runs at rated torque, as well as under overload operating conditions.