Monitoring of journal bearing faults based on motor current signature analysis for induction motors

Most of the failures in oil-lubricated journal bearings are associated with mechanical instabilities produced by lubrication system problems or bearing wear, and result in increased shaft vibration. Therefore, monitoring of the journal bearing condition in the field mainly relies on analysis of proximity probe or accelerometer signals. However, not all motors with journal bearings are equipped with such mechanical sensors due to cost or environmental restrictions. In this paper, the feasibility of applying motor current signature analysis (MCSA) for remote monitoring of mechanical instabilities in journal bearings produced by oil whirl and bearing clearance problems, is evaluated. In addition, a small-scale journal bearing test setup that can be implemented in low voltage motors for testing journal bearing faults under controlled conditions, is presented. An experimental study on a sealless fuel pump motor operating in the field, and on the custom-built journal bearing motor test setup shows that MCSA is capable of providing remote monitoring of journal bearing oil whirl and increased clearance for potentially preventing motor failure. The results of vibration analysis are also presented for comparative evaluation.