Slip-related vibration
http://www.dliengineering.com/vibman/sliprelatedvibration.ht...

Irregularities in the rotor bars will cause vibration at the slip frequency times the number of poles in the motor. For instance, in a two-pole motor, any particular rotor bar will be aligned with the rotating magnetic pole created by the stator at two times for every "slip cycle". The slip cycle is the synchronous speed divided by the slip speed. For instance, in a 3450 RPM motor, the synchronous speed is 3600 RPM, and the slip frequency is 3600 - 3450 = 150 RPM. Then, 3600 ¸ 150 = 24, which is the slip cycle. This means for every 24 revolutions of the rotor, the same rotor bar will be exactly aligned with the same polarity of the rotating magnetic pole, and will be aligned with the opposite rotating pole once every 12 revolutions.
If one rotor bar has more resistance than the others due to a crack or break, it will have less current induced in it when it is aligned with the poles, and this will produce a little less torque at this point in its slip cycle. Thus, the torque will be modulated at the slip frequency times twice the number of poles. This frequency is also called the pole pass frequency. Pole pass is seen in a vibration component in the signature, and also results in sidebands around the 1X vibration component and around the 120 Hz component.

. זאת, כדי לקיים את התנאים להשראת כח אלקטרו מניע וקיום זרם בסלילי הרוטור. ההפרש s בין המהירויות נקרא "חליקה" (slip).

An asynchronous motor requires slip - relative movement between the magnetic field (generated by the stator) and a winding set (the rotor) to induce current in the rotor by mutual inductance.