Modelling of failure states of induction machines

The paper presents the mathematical model of a squirrel cage induction motor with higher space harmonics taken into account and the computer simulation of induction motor fault states. We have studied the case of broken rotor bars as the source of rotor electrical asymmetry. Based on the mathematical model, the computer simulation of the influence of rotor cage defect on magnetic field distribution in the cross-section, torque and stator current characteristics of induction machine at different slip values, is performed. The laboratory tests of a healthy motor and one with broken rotor bars show good agreement with simulation results. The ability to model different types of failure states with a digital computer represents a modern practical tool for monitoring and diagnostics of the possible defects or emergency states of industrial drives.