An Approach for Estimating the Cogging Torque Performance Considering Manufacturing Uncertainties for the IPM Machine

The design tolerances and material defects are frequently inevitable in the real manufacturing process, where unexpected additional cogging torque might be caused as a result. An approach fast estimating the design performances under manufacturing uncertainties is highly expected. In this paper, the previously proposed worst-uncertain-combination-analysis (WUCA) approach is further modified, where the influences of rotor geometries could be taken into account. A 10-pole-12-slot (10P12S) permanent magnet (PM) machine with non-uniform air-gap considering the rotor uncertainties is taken as an example. The cogging torque robustness for designs with different air-gap saliency ratios are discussed and compared. A medium value of air-gap saliency is suggested to achieve a balance between the ideal and worst-scenario performance under rotor uncertainties. Three prototypes with different air-gap saliency ratios are manufactured, where the possibly worst-case under uncertainties are imitated with a special PM assembling sequence. The deduction is then verified by the experimental results of the prototypes.