Induction Motor Slot Combinations Rules to Predetermine Crawling, Vibration, Noise and Hooks in the Speed-Torque Curve

A theory of coexisting stationary and rotating slot openings is developed with the aid of ``revolving permeances,´´ and the magnitude and speed of the parasitic fluxes due to the slot openings and the fundamental current density wave are found. It is shown that the interaction of the fundamental flux and a parasitic flux of the same order of magnitude as the fundamental flux causes the vibrations, objectionable noises, and crawlings of induction motors. The existence of these ruinous irregularities depends only in the difference of slots, the number of poles, and in some cases on the critical speeds of the rotor for circular or tortional vibrations, and is independent of the number of phases or the type of winding. Three rules are developed for the determination of destructive vibrations and noise, eight rules for establishing crawling speeds, and eight rules for finding hooks in the speed-torque curves of induction motors.