Eccentricity Fault Diagnosis in Permanent-Magnet Synchronous Motors Using the Stray Flux Vector

This paper introduces a method for detecting rotor eccentricity in Permanent Magnet Synchronous Motors (PMSMs) by monitoring the stray magnetic flux outside the stator yoke. Three sensors are strategically placed at intervals of 120 mechanical degrees around the stator to measure the stray flux. This architectural design enables the representation of the stray flux using a zero-sequence component and a space vector, following the Vector Space Decomposition (VSD) technique. The stray flux is analyzed for each of the three types of eccentricity that the motor may experience, i.e., static, dynamic, and mixed eccentricity. In this study, the stray flux is demonstrated to be a highly reliable condition monitoring indicator, providing significant motor health-related information, particularly when a closed-loop control is employed to keep the stator currents as sinusoidal as possible, even during a failure scenario. The effectiveness of the proposed approach has been verified by Finite Element Method (FEM) simulations.