A new method for broken rotor bars and load oscillation diagnosis on induction motors is presented. The proposed strategy is based on the decomposition of the stator currents into their instantaneous active and reactive current components. Such components allow the decoupling of the effects produced by rotor asymmetries from those produced by oscillating loads. This allows not only the proper fault detection but also a correct fault diagnosis. Simulation and experimental results, both from laboratory and industrial cases, are presented to validate the proposal.

The problem of angular shaft misalignment in motors-load systems coupled through flexible couplings is analyzed in this work. A model for the analysis and diagnosis of angular misalignment in induction motors is presented. It allows studying the angular shaft misalignment effects over the motor torque, instantaneous power and currents through dynamic simulation. Additional effects introduced by the mixed eccentricity produced by the shaft misalignment are also analyzed through experiments. The results show that angular misalignment can be detected from electrical motor variables, but its correct diagnosis is difficult. The study is completed by vibration and thermography analysis.