Comparison of dynamic responses for IPM and SPM motors by considering mechanical and magnetic coupling

The permanent magnet motor is often the most important element in high performance rotor applications and also a frequent source of vibration and acoustic noise. Because of manufacturing imprecision such as mass unbalance, shaft bow and bearing tolerances, rotor eccentricity extensively exists in all kinds of electric machines. This paper investigates magnetic unbalanced forces for IPM and SPM motors which are widely used in a washing machine due to high average torque and dynamic responses of a rotor motor system when rotor eccentricity exists. For the magnetic field analysis, a finite element method is used to account for the magnetic saturation and rotor eccentricity. An IPM motor, mostly chosen to realize high speed operation, shows a worse effect on magnetic unbalanced forces and dynamic responses compared with SPM motor due to magnetic saturation when the eccentricity exists.