Comparison of magnetic forces for IPM and SPM motor with rotor eccentricity

The permanent magnet motor is often the most important element in many prec ision rotor applications and also a frequent source of vibration and acoust ic noise. The eccentricity between stator and rotor is inevitably introduce d during manufacturing process, such as mass unbalance, shaft bow and beari ng tolerances. This paper investigates radial force density and magnetic un balanced force for IPM and SPM motors when rotor eccentricity exists. For t he magnetic field analysis, a finite element method is used to account for the magnetic saturation and rotor eccentricity. The radial force density an d magnetic unbalanced force are analyzed by Maxwell stress tensor and discr ete Fourier transform. An IPM BLDC motor, mostly chosen to realize high spe ed operation, is significantly affected by rotor eccentricity due to magnet ic saturation.