An Odd Number of Pole Pairs to Minimize Cogging Torque With Mechanical Symmetry Preserved

Permanent Magnet (PM) machines are becoming popular in industrial applications as they offer brushless solutions and high torque density, high efficiency compared to conventional electrical machines. One of the major issues of PM machines is torque ripple which is intrinsic in their design. Cogging torque is one of the major components which contribute to torque ripple. This work tries to minimize cogging torque in a 4 pole surface mounted permanent magnet synchronous machines (SPMSM) with PM shifting. But shifting of the PMs causes mechanical asymmetry. Centre of mass of the PM is deviated due to asymmetrical distribution of the PMs. Cogging torque is minimized with PM shifting with mechanical symmetry preserved for an odd number of pole pairs i.e. 6 pole machines by keeping the slots per pole pair and kVA rating of the machine same.