Static eccentricity fault diagnosis using the signatures analysis of stator current and air gap magnetic flux by finite element method in saturated induction motors

Abstract

Static eccentricity produces low frequency air gap flux components, however they can be observed in stator current spectrum only under mixed eccentricity, and for high degrees of rotor shifting. Unlike motor current signature analysis, the air-gap magnetic flux signature analysis allows to detect small degree of purely static eccentricity. The simulation results are obtained by using time stepping finite elements method. In order to indicate the influence of the magnetic saturation upon the analysis of the faulty induction motor, two constant and non-liner permeability; are included in this paper. It is shown that the fault index amplitudes of obtained signals from the constant permeability are larger than that of the real case. In this paper the amplitudes of characteristic frequency components $$ f_{ecc} = \left| {f_{s} \pm k{\kern 1pt} f_{r} } \right| $$ with low degrees of purely static eccentricity fault are detected using air-gap magnetic flux signature analysis. Moreover, new index signatures are detected around the third time harmonics in air-gap magnetic flux density spectrum for saturated motor, those components are expressed by $$ f_{ecc} = mf_{s} \pm f_{r} $$ .