Induction Motors Vibration Monitoring Using a Biaxial Optical Fiber Accelerometer

Abstract

In this paper, the implementation, characterization, calibration, and testing of a biaxial optical fiber accelerometer for vibration monitoring in three-phase induction motors is presented. The optical sensor uses fiber Bragg gratings to measure the displacement of an inertial mass relatively to a support base. The sensor characterization was measured through the impact hammer, allowing the determination of the natural frequencies in both sensitive directions, the values of 747.5 Hz and 757.5 Hz were estimated for the $x$ -axis and the $y$ -axis, respectively. For calibration, an electromagnetic exciter was used to introduce a controlled harmonic excitation at different frequencies, with this analysis, a high SNR was observed, on average over 30 dB for both sensitive directions, and a sensitivity of 100 pm x $\cdot \text{g}^{-1}$ was obtained, up to one third of the natural frequency, in each direction. The tests were developed with the main aim of the analysis in induction motors based in vibration monitoring, the analysis can help to prevent wear in motors, increasing its efficiency, and lowering maintenance costs. The optical accelerometer measurements were compared with the ones from a capacitive sensor, during regular operation and with a broken rotor bar operating with 75% and 100% load. The performed tests with the optical sensor allowed to successfully analyze the frequency components, and its changes, for the regular and damage operation.