Structural Analysis of a High Speed Double-Sided Axial Flux Permanent Magnet Motor Vertically Suspended by Magnetic Bearings

This paper presents the mechanical vibration and stress analysis of an axial flux permanent magnet (AFPM) motor for a high speed (30000 rev/min) rotor which is vertically suspended by active and hybrid magnetic bearings. In the analysis, a prototype AFPM motor with a double sided rotor and a coreless stator between the rotors are considered. Rotor disks of the motor are constructed of two 10 mm-thick steel disks with 6.35 mm-thick permanent magnets which represent around 70% of the total weight of the machine. Firstly, an analytical solution is carried out to determine natural frequencies of the rotor-shaft system. Then rotor disk thickness was determined based on a rotor axial displacement due to the attractive force between the permanent magnets placed on opposite rotor disks. Finally, 3D finite elements analysis (FEA) are carried out to verify the analytical results.