A new diagnostic instrument to detect generalized roughness in rolling bearings for induction motors

In this paper the external stray flux around a motor has been investigated as a possible new diagnostic instrument to detect generalized roughness. This very common bearing fault has been slightly considered in the literature so far. Stray flux was measured by two probes, one commercially available and one realized in laboratory; the diagnostic content of both signals has been compared also with the measurement of the stator current. The experimental tests have been carried out on an induction motor by substituting one of its bearings with an artificially damaged one, according to three steps of progressive wear. The three measured variables have been analyzed in the frequency domain, by evaluating in particular the characteristic frequencies of the single-point bearing defects. The diagnostic content of the stray flux has been discovered as definitely higher with respect to the stator current and therefore its use to detect generalized roughness is promising.