An Overview of Rotor Losses Determination in Three-Phase Fractional-Slot PM Machines

Three-phase fractional-slot PM machines are more and more used in many applications. In spite of the several advantages, these machines exhibit high contents of space harmonics in the air-gap MMF distribution, whose amplitude depends on the particular combination of number of slots and poles. The main consequence of such harmonic contents is the induced losses in the rotor. The aim of this paper is to link the rotor losses to the combination of slots and poles of the PM machine. The effort is to determine a general rule to single out easily if a machine topology is suitable or not, as far as the rotor losses are concerned. Both overlapped and non-overlapped coil fractional-slot windings are considered.