3D permeance model of induction machines taking into account saturation effects and its connection with stator current and shaft speed spectra

This study presents a 3D-permeance model of induction machines that reproduces the axial evolution of the air-gap flux for skewed rotors. This evolution is presented using the terminology of axial magnetic modes. These axial waves are the result of the interaction between the rotor slot harmonics permeance series and the space harmonic index related to the magneto-motive force generated by the skewed rotor cage. Wavelength of this axial mode is compared with the results of a validated multi-slice finite element model. Axial wave modes in the slice model were processed using estimation techniques giving an excellent matching with the results of the permeance model. Experimental validation has been indirectly carried out comparing different spectral components for both skewed and non-skewed identical motors and comparing their magnitudes. Differences in the magnitude are associated with the existence of axial modes that change the total flux contained in the air gap of the motor. This study mainly focuses on the study of saturation harmonic.