Slot combinations of induction motors

AMONG the suggestions advanced as to the cause of irregularities in the shape of the speed-torque curves of polyphase induction motors which cause them to crawl at reduced speeds or to have excessive vibration and noise, is that the harmonic fluxes introduced by the distribution of the stator and rotor windings in slots may cause these irregularities. However, the conclusions of this analysis are not borne out by the facts, and the investigations on which this article is based show that the most powerful disturbing effects are due not to the distribution of the windings, but to the presence of the slot openings in the stator and rotor.