Reduction of Cogging Torque and EMF Harmonics in Modulated Pole Machines

This paper discusses a method for reducing cogging torque and harmonic content of back-electromotive force (EMF) waveforms in modulated pole machines (MPMs). Tooth pitching is applied to a separate phase MPM in order to reduce the most prominent harmonics present in a three-phase MPM's cogging torque. Experimental results show that the application of tooth pitching to these machines can reduce the cogging torque and back-EMF harmonics significantly. This comes without a significant impact to the useful output of the machine, which is confirmed by the comparison of measured results for two prototypes. Such a technique can be easily applied to existing machine designs without the need for extra components and for the same production cost.