Concentrated winding axial flux permanent magnet motor for industrial use

This paper introduces a new cost-effective, energy-saving, axial flux permanent magnet (PM) motor type for industrial use. The particular features of the machine are based on the study of using concentrated winding open slot constructions of permanent magnet synchronous machines in the normal speed ranges of industrial motors, for instance up to 3000 min^-1, without excessive rotor losses. In an axial flux permanent magnet motor with the two-stator-single-rotor construction, where the magnetic flux travels through the permanent magnets from one stator to another, the rotor of the machine can be kept totally ironless. If the open stator slot structure can be used with concentrated windings, prefabricated coils can simply be inserted around the stator teeth, and the winding process becomes very cost-effective compared for example with double-layer short-pitched normal integral slot windings. However, open slots expose rotor surface magnets to large flux pulsations, and the losses of bulky sintered magnets cannot be neglected. Divided sintered neodymium iron boron (NdFeB) magnets may be used instead, but the magnet configuration must be carefully analyzed to attain an acceptable eddy current loss level in the magnets.