Monitoring Journal-Bearing Faults: Making Use of 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 the journal-bearing condition in the field relies mainly on the 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 article, we evaluate the feasibility of applying motor current signature analysis (MCSA) for the remote monitoring of mechanical instabilities in journal bearings produced by oil-whirl and bearing-clearance problems. In addition, we present a small-scale journal-bearing test setup that can be implemented in low-voltage motors for testing journal-bearing faults under controlled conditions. 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 can remotely monitor journal-bearing oil whirl and excessive clearance to prevent motor failure. The results of vibration analysis are also presented for comparative evaluation.

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