Diagnosis of Bearing Faults in Induction Machines by Vibration or Current Signals: a Critical Comparison

Mechanical imbalances and bearing faults account for a large majority of faults in a machine, especially for smallmedium size machines. Therefore their diagnosis is an intensively investigated field of research. Recently many research activities were focused on the diagnosis of bearing faults by current signal. This paper compares the bearing fault detection capability obtained with vibration and current signals. The paper contribution is the use of a simple and effective signal processing technique for both current and vibration signals, and a theoretical analysis of the physical link between faults, modeled as a torque disturbance, and current components. The focus of the paper is on the theoretical development between torsional torque and current component amplitudes and a review of fault models used in literature. Another contribution is the realization of realistic incipient faults and their experimental validation. Radial effects are visible only in case of large failures that result in air-gap variations. Experiments are reported that confirm the proposed approach.