Application of a finite element method to predict damaged induction motor performance

The paper presents the application of a finite element method for predicting the performance of induction motor having electric and magnetic asymmetry of the rotor cage due to some broken rotor bars. Quantities like magnetic vector potential, flux density, force components, rotor and stator currents, mutual and leakage inductance were determined very precisely. The paper takes into account the magnetic materials nonlinearity. The detailed insight in magnetic field distribution of a squirrel cage induction motor forms the basis for further evaluation of its operational behavior. Increasing anomaly in magnetic field distribution due to the increasing number of broken rotor bars results in a degradation of steady-state and dynamic performance of the induction motor and can be determined with computer simulation, eliminating expensive and time consuming laboratory tests. The obtained results are compared with measurements. Correct evaluation of faulty motor performance is a very significant part of condition monitoring and diagnostic procedure in modern supervision systems of electrical drives.