Impact of Asymmetric and Symmetric Overhangs on Torque Quality and Axial Magnetic Force Computations in Surface Mounted PM Synchronous Motors

Permanent magnet (PM) motors have become great alternatives to traditional induction motors. Overhang, on either the rotor or the stator, is commonly used in PM motors. In this study, various alternatives of stator or rotor overhang in PM synchronous motors are investigated in detail. Both asymmetric and symmetric overhang cases are considered in the article. The impact of overhang on the torque quality and torque densities is investigated using 3-D finite element analysis (3D-FEA). Axial magnetic forces during assembly with and without overhang are also simulated and variation of axial force for different cases of overhangs is explored. A prototype PM motor with rotor overhang is used to validate the analyses experimentally.