On the reduction of magnetic pull in induction motors with off-centre rotor

The behavior of an induction motor with off-center rotor is investigated. The Maxwell stress between rotor and stator of an induction machine with static and dynamic eccentricity of the rotor is calculated for two types of connection between stator coils. Theoretical and laboratory results show that connections of coils of the stator winding in parallel, with equalizing branches, lead to drastic reduction in unbalanced magnetic pull. This reduction prevents problems of magnetic pull in machines with imperfectly centered rotors. A secondary effect of minor importance is the appearance of a vibrational component in the magnetic pull, with an amplitude less than 26% of that of the fundamental force component.>