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 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 and without the need for extra components. Such a technique can be easily applied to existing machine designs without increasing the production cost.