Detection of winding asymmetries in wound-rotor induction motors via transient analysis of the external magnetic field
Résumé
In recent years wound-rotor induction motors (WRIM) have received special attention because of their broad use as generators in wind turbine units as well as in some large power applications in industrial plants. Some classical approaches perform the detection of certain faults based on the FFT analysis of the steady state current (MCSA); they have been lately complemented with new transient time-frequency-based techniques to avoid false alarms. Nonetheless, there is still a need to improve the already existing methods to overcome their remaining drawbacks and increase the reliability of the diagnostic. In this regard, emergent technologies are being explored, such as the analysis of stray flux at the vicinity of the motor. Recently, this technique has been applied to detect broken rotor bar failures and misalignments in cage motors, avoiding some drawbacks of well-established tools. However, the application of these techniques to WRIM has not been studied. This work explores the analysis of the external magnetic field under the starting to detect rotor winding asymmetry defects in WRIM by using advanced signal processing techniques. Moreover, a new fault indicator based on this quantity is introduced, demonstrating the potential of this technique to quantify and monitor rotor winding asymmetries in WRIM.