FAULT DIAGNOSIS OF INDUCTION MOTOR USING CURRENT SIGNATURE

Abstract

This work addresses the application of motor current signature analysis for the detection of various faults in induction machines. Vibration monitoring is currently used to detect the presence of a fault condition. Since these mechanical vibrations are associated with vibrations in the physical air gap of the machine, the air gap flux density is modulated and stator currents are generated at predictable frequencies related to the electrical supply and vibrational frequencies. This work takes the initial step of investigating the efficacy of current monitoring for fault detection by correlating the relationship between vibration and current frequencies caused by incipient bearing failures and supply unbalance. The bearing frequencies associated with the physical dimensions and construction of the bearings are defined. The effects on the stator current spectrum due to bearing conditions are described. This is an important result in the formulation of a fault detection scheme that monitors the stator currents. Experimental results which show the vibration and current spectra of an induction machine with different bearing faults are used to verify the relationship between the vibrational and current frequencies. The test results clearly illustrate that the stator current signature can be used to identify the presence of a fault. vi