In-Situ Thermal and Mechanical Fibre Optic Sensing for In-Service Electric Machinery Bearing Condition Monitoring

This paper reports a feasibility study of fibre Bragg Grating (FBG) sensing application for simultaneous extraction of thermal and mechanical information on electric machine bearings operational status for condition monitoring purposes from the same optical sensing head. The underlying aim is to examine the potential of using the readings from a single FBG head embedded in the bearing structure to infer information on both thermal and mechanical operating conditions observed at sensor location. To this end, experiments were undertaken on an FBG instrumented drive-end bearing of an operating inverter driven squirrel cage induction motor. Key features of the in-situ FBG sensor design, installation and calibration procedures along with the analysis of the obtained experimental measurements are reported. It is shown that the acquired measurements contain concurrent thermal and mechanical information that can be distinguished to enable understanding of the examined motor bearing thermal only and mechanical only operating conditions.