Influence of the magnetic steel encasing of induction motors on the efficiency of the rotor faults diagnosis based on the harmonics of the coil sensors output voltage

Abstract

This paper deals with the influence of the magnetic steel encasing of squirrel cage induction motors on the efficiency of one broken bar and rotor dynamic eccentricity faults diagnosis based on the harmonics of the output voltage of coil sensors placed outside the motor. The effects of the rotor faults on the electromagnetic torque and on the unbalanced force of rotor - stator interaction are evaluated. The most important harmonics for fault diagnosis are determined for a high power low rated slip motor, without and with a magnetic steel encasing thick enough with respect the penetration depth of the main traveling field of the motor.