Analytical Armature Reaction Field Distribution of Slotless Brushless Machines With Inset Permanent Magnets

An analytical armature reaction magnetic field calculation is proposed for slotless brushless machines with inset permanent magnets (PMs). The rotor/stator back-irons are assumed to have infinite permeability and therefore the analytical solutions are obtained for the winding, air-gap, and magnets regions. The analytical expressions can be used for the brushless slotless surface-inset PM machines with any armature current waveform and any number of phases. The effects of the iron inter-poles on the armature reaction field have been studied. To verify the model, the analytical results have been compared with those obtained from finite-element analyses (FEA).