Stator Current and Motor Efficiency as Indicators for Different Types of Bearing Faults in Induction Motors

This paper proposes a new approach to use stator current and efficiency of induction motors as indicators of rolling-bearing faults. After a presentation of the state of the art about condition monitoring of vibration and motor current for the diagnostics of bearings, this paper illustrates the experimental results on four different types of bearing defects: crack in the outer race, hole in the outer race, deformation of the seal, and corrosion. The first and third faults have not been previously considered in the literature, with the latter being analyzed in other research works, even if obtained in a different way. Another novelty introduced by this paper is the analysis of the decrease in efficiency of the motor with a double purpose: as alarm of incipient faults and as evaluation of the extent of energy waste resulting from the lasting of the fault condition before the breakdown of the machine.