Influence of MMF Harmonics on the Iron Losses of Permanent Magnet Synchronous Machines

Permanent magnet synchronous machines have several advantages like high torque density, small torque ripple and well-established control strategies. Especially the machines with concentrated fractional-slot winding are in the focus of research due to their high winding factor. However, these kinds of windings have some drawbacks due to the high content of harmonics and sub-harmonics of the magnetomotive force in the air gap of the machine. A significant amount of iron losses in the stator and rotor as well as eddy-current losses in the permanent magnets are the consequences. In this paper, the influence of the harmonics and subharmonics as well as the fundamental wave on the machine losses are discussed. With three different models the influences of the harmonics are studied. It is shown that different harmonic orders of the magnetomotive force spectrum have significantly different influences on the stator-, rotor- and permanent magnet losses.