Detection of induction motor faults: A comparison of stator current, vibration and acoustic methods

In this paper we present the comparison results of induction motor fault detection using stator current, vibration, and acoustic methods. A broken rotor bar fault and a combination of bearing faults (inner race, outer race, and rolling element faults) were induced into variable speed three-phase induction motors. Both healthy and faulty signatures were acquired under different speed and load conditions. To address the detection capabilities of the above methods, comparisons are made in both the time and joint time-frequency domains. In the frequency domain, spectral differences are compared and characterized under constant speed conditions. To evaluate the detection sensitivities under non-stationary conditions (e.g. startup), a joint time-frequency method called the smoothed pseudo Wigner-Ville distribution (SPYWD) is employed to analyze non-stationary signatures. The SPWVD is a powerful technique for revealing non-stationary characteristics of motor signatures. Experimental results show that the stator current method is sensitive to the broken rotor bar fault while the vibration method is sensitive to bearing faults. The acoustic method is very attractive in that it contains less noise and interference within the analyzing frequency band. With the proper selection of monitoring and analysis methods, induction motor faults can be detected accurately under both stationary and non-stationary states.