Effects of Magnetostriction on Electromagnetic Motor Vibration at Sideband Frequencies

This paper discusses the effects of magnetostrictions (MSs) on the vibrations of stator core of electric motor driven by pulse width modulation controllers. Special attention is given to the vibration shapes at the sideband frequencies of the switching frequency. First, based on the measured vibration shapes of an electric motor, it is shown that the vibration shapes at the sideband frequencies are strongly affected by the electromagnetic force (EM) distribution. Next, we estimate the vibration shapes of the stator by conducting coupled magnetostatic and structural finite-element analyses. It is shown that the computed and the measured vibration shapes at each sideband frequency are in good agreement. It is then demonstrated that the contributions of the EM and the MS on the stator vibration shape at each side band frequency can clearly be explained by the phase pattern of magnetic flux density on the stator teeth and back yoke of the stator core.