Analytical determination of the instantaneous airgap field in a brushless permanent magnet DC motor

An analytical technique is presented for predicting the airgap field distribution in radial-field topologies of brushless motors under any load condition, accounting implicitly for the corresponding stator winding current waveforms and the effects of stator slot-openings. It is based on a 2-D analysis of the airgap/permanent magnet region, and combines an analytical calculation of the armature reaction field with an analytical prediction of the phase current waveforms and the field produced by the magnets to permit the instantaneous field distribution to be predicted under any steady-state load and specified commutation strategy