Diagnosis and characterization of effects of broken bars and connectors idsquirrel-cage induction motors by a time-stepping coupled finite element-state space modeling approach

In this paper, a comprehensive presentation of a Time-Stepping Coupled Fini te Element-State Space modeling approach for diagnosis and characterization of effects of rotor (cage) broken bars and connectors in squirrel-cage ind uction motors is given. The model is used to compute/predict the characteri stic frequency components which are indicative of rotor bar and connector b reakages in the armature current waveforms and developed torque profiles, r espectively. It was found that failures due to rotor connector breakages te nd to degrade the developed torque of the machine considerably more than fa ilures due to rotor bar breakages. Also, the effects and implications of ro tor breakages on core loss distributions are quantified and described. Furt hermore, this model has great potential in future applications to generate data bases for use in overall non-invasive diagnostics of faults or trouble shooting in relation to quality assessments of the state of the motor and the overall drive.