A method to estimate the worst-case torque ripple under manufacturing uncertainties for permanent magnet synchronous machines

The influences of manufacturing uncertainties on the cogging torque of permanent-magnet (PM) motor have been widely examined, and they are usually estimated by calculating and comparing several design models featuring small deviations to their ideal counterpart. To achieve high quality of the analysis results within a reasonable calculation time, a suitable selection of design variants featuring uncertainties for evaluation are crucial. However, lack of knowledge of the relationship between torque variations and uncertainties, a proper selection is difficult to accomplish. In the previous work related to the worst-uncertaincombination-analysis (WUCA) method, efforts were made to reveal the relationship between the additional cogging torque harmonics and combinations of uncertainties. In this paper, the WUCA method is extended to estimate the on-load torque ripple performance under manufacturing uncertainties in this paper, and its effectiveness in terms of identifying the worst-case combinations is verified through finite element analysis.