Detection of incipient rotor cage fault and mechanical abnormalities in induction motor using global modulation index on the line current spectrum

Asynchronous motors is nowadays the most used in industrial process. In this paper we describe a new approach to detect incipient broken rotor bar and mechanical abnormalities. We use the magnitude of components created in the line current and the instantaneous power spectra of one stator phase to detect the presence of these faults in induction motors. We show that the study of components created by space harmonics in the stator current allows us to differentiate a broken rotor bar to a load torque variation. First, we have looked the effects of these faults with a simulation model. Tanks to this study, fault components we have to supervise are localized in power spectra. Secondly, a load torque oscillation and several rotor cage faults were studied with various load level. Experimental results prove the efficiency of the proposed method.