Computationally Efficient Method for Identifying Manufacturing Induced Rotor and Stator Misalignment in Permanent Magnet Brushless Machines

A computationally efficient method is presented to investigate additional cogging torque harmonics resulting from misalignment of the rotor and stator caused by assembly and manufacturing tolerances in an axial flux fractional pitch permanent magnet synchronous machine (PMSM). The superposition method creates a complete cogging torque profile by using a library of pole transitions over a single stator slot. The method extends previously published work, and is used to predict the effect of eccentricity misalignment in combination with pole and slot placement inaccuracies on cogging torque. Experimental data are presented supporting the superposition data indicating that static and dynamic eccentricity produce first- and second-order sidebands about the rotor and stator affected harmonics, respectively. There is good agreement between the hybrid superposition method, FEA, and measured experimental data.