Rotor eccentricity fault detection of a DC motor

Abstract

This paper presents a model of the DC motor with an eccentric rotor. The winding function theory shows the effect of the eccentricity fault on the motor inductances and simulation is done using a nonsymmetric air-gap function. A modified equation is presented to describe the rotor slot harmonics in the DC motor. To detect the fault, a pattern recognition technique is utilized. The proposed algorithm works at steady state and uses armature current as input. In order to provide the appropriate feature for the classifier, the rotor speed is needed, therefore the speed is estimated from armature current, using commutation harmonics. The experimental results obtained from a 3 hp shunt DC motor shows the strength of this method. In order to cover many different motor load conditions, data are collected at different speeds for both a healthy DC motor and a DC motor with an unbalance load which can simulate static eccentricity.