Corrosion Model of a Rotor-Bar-Under-Fault Progress in Induction Motors

A corrosion model of a rotor-bar-under-fault progress in induction motors is presented for simulations of induction machines with a rotor-bar fault. A rotor-bar model is derived from the electromagnetic theory. A leakage inductance of the corrosion model of a rotor bar is calculated from the relations of magnetic energy, inductance, current, and magnetic-field intensity by Ampere's law. The leakage inductance and resistance of a rotor bar varies when the rotor bar rusts. In addition, the skin effect is considered to establish the practical model of a rotor bar. Consequently, the variation of resistance and leakage inductance has an effect on the results of motor dynamic simulations and experiments, since a corrosive rotor bar is one model of a rotor bar in fault progress. The results of simulations and experiments are shown to be in good agreement with the spectral analysis of stator-current harmonics. From the proposed corrosion model, motor current signature analysis can detect the fault of a corrosive rotor bar as the progress of a rotor-bar fault. Computer simulations were achieved using the MATLAB Simulink with an electrical model of a 3.7-kW, three-phase, and squirrel-cage induction motor. Also, experimental results were obtained by real induction motors, which had the same specification as the electrical model used in the simulation