A study of 2sf beat phenomena in induction motors

The induction motor sometimes produces beatlike vibration and noise at 2sf Hz, i.e., the frequency twice as high as the slip frequency (2sf beat phenomena). It is shown experimentally that 2sf beat phenomena are caused by the dynamic eccentricity component at the rotor. The authors classified the rotor eccentricities into four forms and prepared four experimental motors corresponding to the four forms. Significant 2sf beat phenomena are accompanied by resonance phenomena of the mechanical system. The 2sf beat phenomena occur at a certain frequency (carrier wave) and are significantly not related to vibration and noise of other frequency components