Rotor broken-bar fault diagnosis of induction motor based on HHT of the startup electromagnetic torque

This paper presents a new method for rotor broken-bar fault diagnosis of induction motors.The asymmetry of the rotor caused by broken-bar fault will give rise to the appearance of additional frequency component of 2 s sf(s is slip and s f is supply frequency)in the electromagnetic torque spectrum.The startup electromagnetic torque signal is decomposed into several intrinsic mode function(IMF)with empirical mode decomposition(EMD)based on the Hilbert-Huang Transform.Then,using the instantaneous frequency extraction principle of the Hilbert Transform,the rotor broken-bar fault characteristic frequency of 2 s sf can be exactly extracted from the IMF component,which includes the rotor fault information.Moreover,the magnitude of the IMF which includes the rotor fault information can also give the number of rotor broken bars.Experimental results demonstrate that the proposed electromagnetic torque-based fault diagnosis method is feasible.