Vibration in 2-pole induction motors

VIBRATION and noise in a 3-phase 2-pole a-c motor quite often are characterized by a pulsation or “beat” in the amplitude. That is, the amplitude of the vibration and noise increases and decreases at a uniform frequency which is related to the slip of the rotor. In many applications, these pulsations are not detrimental to the performance of the machine, but they do have an adverse psychological effect upon anyone in the vicinity, because a pulsating noise is much more noticeable than a steady one.