Rotordynamic Analysis and Comparative Study of High-Speed Outer Rotor Permanent Magnet Motor Designs

High-power density electric motor designs are a requirement in aerospace and automotive applications. Outer rotor permanent magnet motors can offer high power density but have mechanical challenges such as structural stability and rotodynamic issues. In this work, a rotodynamic study was performed for two outer rotor permanent magnet motor designs. The first design was a cantilever design in which the rotor was suspended at one end, supported by four bearings; in the second design, the rotor was simply supported by two bearings in each end. Two different finite element method-based approaches, solid rotor and beam rotor methods, were used to extract the critical speed.