Diagnosis of Mixed Eccentricity in 400 kW Induction Machine Based on Inspection of Stator Current Spectrums

This paper dealing with diagnosis of induction machines affected by combined eccentricity via analyzing the sator curents, inspection of the current spectrums and predict the harmonics that present in the spectrums and represent an indication for this ailment . The machine under invistigation is a 400 kW, four pole-pair, squarelcage induction machine. The current spectrums were calculated for the cases of full symmetry and mixed eccentricity. The calculations presented in this paper, are based on the poly-harmonic model that accounting for static and dynamic eccentricity, stator and rotor slotting, parallel branches as well as cage asymmetry. The calculations were followed by Fourier analysis of the stator currents in steady state operation. The inspection of the current spectrums focusing on two main zones these are the 50 Hz fundamental harmonic zone and the main slot harmonic zone. The paper will include the zooms of the above mentioned zones to demonstrate the harmonics presented in each zone. The calculated spectrums will be compared with the spectrums of the real measured currents.