Javier Martinez

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.

SUMMARY: This paper presents a finite element model for the development of stator current diagnosis techniques based on the spectral analysis of the state variables on induction motor. Non‐linearities terms existing in the stator current due to the fault are analysed and concluding that these indicators can lead to a frequency matching of harmonics related to broken bar fault. In addition, this paper covers the limitations that two‐dimensional finite element models are having with respect to conical eccentricity and axial effects in the electric device. Copyright © 2013 John Wiley & Sons, Ltd.

The study presents analysis of the broken bar induction machine, through numerical, analytical and experimental investigations. Numerical finite element analysis is carried out with a commercial software in which coupling between the windings circuit equations and equations of the magnetic field has been implemented and verified through intensive measurements. An analytical model has also been constructed to understand and explain the origin of different frequencies detected in the case of broken bars. The analytical model enabled prediction of frequencies, in a new manner, when the number of consecutive broken bars increases. The novelty of this study arises from derivation of an expression linking stator current harmonics (using the wave number of a broken cage), slip harmonic and saturation harmonic, which is closely related to the number of consecutive broken bars. The model also takes into account the speed ripple. This expression has been validated by both finite element model (FEM) and measurements on a 22 kW induction machine with healthy and faulty rotors.