Detection of eccentricity and bearings fault using stray flux monitoring

The article describes the possibilities of employment of external magnetic field for detection of rotor eccentricity and for bearing fault diagnosis. Proposed method uses the magnetic flux density in proximity of induction motor as a diagnostic signal and it reaches the relatively high sensitivity in case of rotating air gap asymmetry represented by dynamic eccentricity. Since the bearing fault is the most frequent type of failure, the feasibility of applying this method is investigated. The results of experimental tests are introduced, including the motors with dynamic eccentricity and with artificially damaged bearing on the inner race. Both the stray flux and stator current are measured and compared in frequency domain.