Analysis of the magnetomotive force of a three-phase winding with concentrated coils and different symmetry features

Permanent magnet machines with windings concentrated around each tooth gain more and more importance. In this paper, the magnetomotive force of a three-phase winding with concentrated coils will be analysed. As an example, a machine with a two-coil zone width with opposing flux is regarded. It will be shown that there are two different winding alternatives with four different rotor pole numbers that can generate a constant torque. All these alternative realizations are characterized as fractional-slot windings. This analysis may serve as a basis for the machine design concerning fundamental torque, as well as for acoustic noise calculation because a major part of the harmonic content of the air-gap field is identified.