Review of Design Solutions for Internal Permanent Magnet Machines Cogging Torque Reduction

Internal permanent magnet synchronous machinesare spreading in industrial production.They feature high torque density and extended speed rangethat are key issues in many fields of applications, however theircogging torque is typically quite high.Many methods and design guidelines for cogging torquereduction exist in literature and this paper compares them. Forthis purpose, the different design guidelines are applied to acommon reference machine in order to assess their effectiveness.Computer Finite Element Analysis (FEA) are carried out for eachcase in order to compare the cogging torque reduction capabilityof the different techniques. The side effects of these techniques,such as back-emf and rated torque profile distortions, willbe taken into account. The paper contribution is to comparethe various cogging torque reduction techniques and magneticgeometries on a common reference machine to identify the mosteffective ones.