Manufacturing tolerances: Estimation and prediction of cogging torque influenced by magnetization faults

Permanent magnet excited synchronous motor servo drives are increasingly employed in industrial applications. During mass production deviations from the ideal machine occur. Thereby, parasitic effects such as cogging torque and torque ripple are influenced in particular. For permanent magnet excited machines the magnet´s quality is important. There are many possible failure configurations requiring the study of their influence on the machine´s behavior. In this paper, an approach for the estimation of cogging torque considering magnetization faults is presented. This approach is applied to determine crucial configurations of permanent magnet faults. The intent is to evaluate the influence of the faulty magnetic materials with its asymmetries on the later produced machine. In the process, analytical and numerical methods are combined whereby finally a small computational effort with accurate results is achieved.