The Propagation Mechanism of Fault Signatures in Squirrel Cage Induction Motor Drives

Abstract

This work presents a new approach for analyzing the propagation mechanism of fault signatures in squirrel cage induction motor drives. The used method is based on the analysis of different currents of solid states converters and the fault signatures are investigated when motor is supplied by the volt-per-hertz control mode. Analytical expressions of currents at different location for broken bar, mixed air-gap eccentricity, unbalanced voltage supply are developed using switching functions of both inverter and diode rectifier. Experimental results are provided throughout the paper, to underpin the theoretical analysis. The results show that capacitor current spectrum can give useful information about the state of squirrel cage induction motor. However, due to the low-pass filter composed by capacitor only the fault signatures at low frequency range can be detected from the rectifier supply line current spectrum.