Analytical modelling of unbalanced magnetic pull in isotropic electrical machines

The phenomenon of the unbalanced magnetic pull is analytically modelled, referring to cylindrical rotor a.c. machines. Even if under some simplifications (sinusoidal space distribution of the current density, no slotting, no saturation, no parallel paths), various compact and significant expressions of field and force are obtained, for any number of pole pairs: the model is based on a critical re-formulation of the air-gap m.m.f., by discussing the homopolar term. Some FEM simulations confirm the soundness of the proposed approach.