FBG Thermal Sensing Ring Scheme for Stator Winding Condition Monitoring in PMSMs

This article proposes a random wound stator winding thermal monitoring scheme for permanent-magnet synchronous motors (PMSMs) utilizing an end-winding embedded, ring-shaped, fiber Bragg grating (FBG) thermal sensing array. The scheme enables in situ measurement of winding distributed thermal conditions, which is key to their effective health diagnosis and protection. It is designed to provide a thermal sensing point per each individual end-winding coil-end span and thus enable monitoring of the entire winding structure. This was achieved by utilizing FBG thermal sensing multiplexing in a ring-shaped sensor array inserted into the end-winding assembly to ensure desired in situ placement of separate sensing elements. The scheme was implemented on an inverter-driven PMSM and its performance examined in tests under healthy and faulted winding conditions. The results demonstrate the capability of effective monitoring of healthy windings distributed thermal status and that of unambiguous identification of localized overheating originating from winding fault, providing monitoring functionality that is largely unattainable by conventional thermal sensing techniques. Finally, the proposed scheme also enables straightforward advanced graphical visualization of the windings' thermal status and, hence, a more effective diagnostic interpretation of thermal data to extract knowledge on locations of increased thermal stress.