Application of Stray Flux Analysis for Rotor Fault Detection in Soft-Started Induction Motors

The widespread use of induction motors in industry has led to an increase in the importance of predictive maintenance to avoid untimely shutdowns. On the other hand, their extensive utilization has yielded the proliferation of soft starters that are employed to avoid high currents at start-up. Fault diagnosis techniques such as stray-flux analysis are of interest to diagnose and prevent motor failures. In this regard, this paper studies the validity of the stray-flux-based techniques in motors started via soft-starters. More specifically, it is proposed the analysis of the electromotive forces induced under the starting by the stray-flux in external sensors attached to the motor frame. Various levels of failure at different sensor positions are studied. Finally, a fault severity indicator is introduced based on components energies that appear, and different fault levels are compared. The results enable us to prove the potential of the stray-flux based technique for the rotor condition monitoring of soft-started motors.