[2F1] Loading effect on induction motor diagnostics using motor current signature and vibration analysis
S Ganeriwala
SpectraQuest Inc, USA
Diagnostics of induction motors is a serious issue for improving plant reliability. Broken rotor bars and air gap eccentricity between the rotor and the stator can lead to power loss, a decrease in efficiency, current spikes and other complications resulting in premature failure of the motor. Motor current signature analysis (MCSA) and vibration data are commonly used for diagnosing induction motor problems; however, the effect of mechanical loading on the fault signature is not clear. This paper presents a comparison of vibration and motor current signals for induction motors subjected to different levels of torque, unbalance and misalignment loading air gap eccentricity fault signatures. Experiments were performed on intentionally faulted motors with varying degrees of static air gap eccentricity. Different levels of mechanical torque, unbalance and misalignment loadings were applied to the rotor side. The data was analysed using both vibration and motor current sensors. The results indicate significant components in motor current signature due to rotor eccentricity and torsional mechanical loadings. Vibration spectra do not provide a clear picture of air gap eccentricity fault but vibration data provide a better indication of mechanical faults than the motor current data. The results suggest that both motor current and vibration measurements are required for more complete diagnostics of induction motors.
