Permanent magnet synchronous machines with concentrated coil armature windings: analysis and test validation of Single Stator – Double Rotor, axial flux machines

Some design and operation aspects of axial flux permanent magnet synchronous machines, employing armature windings with concentrated coils wound around the stator teeth, are presented. The e.m.f. control is based on the variation of the windings flux linkage, obtained by modifying the stator (or rotor) configuration. Thanks to the high number of poles and the excellent waveform quality, even with deep field weakening, these machines exhibit a satisfactory operation at low speed, both as generators and motors. In the paper, the main constructive machine features are discussed, together with some design and FEM results. A test on a prototype has also been carried out.