Magnetic and Structural Finite Element Analysis of Rotor Vibrations Due to Magnetic Forces in IPM Motor

We present a method to analyze magnetically induced rotor vibrations in an interior permanent magnet motor by simultaneously considering the excitation of radial, tangential, and axial magnetic forces and the gyroscopic effect. We show that the magnetic forces acting on rotor poles are multiples of the half slot harmonic originating from A+A-B-B+C+C- winding as well as slot harmonics. We determine the equivalent friction forces of ball bearings and apply them to the structural finite element model to prevent numerical divergence of angular velocity of the rotor. The results of simulation show that rotor vibrations are mainly affected by the slot harmonics of the magnetic forces, and it was validated by the experiments measuring rotor vibrations with an accelerometer and a slip ring.