Estimation of stray losses of skewed rotor induction motors using coupled 2-D and 3-D time stepping finite element methods

A precise estimation of stray losses in skewed rotor induction motors is an important and yet very challenging topic for machine designers. Methods for evaluating the stray losses in skewed rotor induction motors by coupling a 2-D multi-slice time stepping finite element model into a 3-D time stepping finite element method are presented in this paper. The model can take into account the inter-bar currents which are ignored if a 2-D finite element model only is used. New formulae, which are based on the actual changes in the magnetic flux densities and can be easily coupled into a time stepping finite element method for estimating the iron losses, are also described.