Open Circuit Fault Detection in Stranded PMSM Windings Using Embedded FBG Thermal Sensors

Detection of winding faults in permanent magnet synchronous machines (PMSMs) with stranded winding designs remains a challenging task for conventional diagnostic techniques. This paper proposes a new sensing approach to this problem by investigating the application of dedicated electrically non-conductive and electromagnetic interference immune fibre Bragg grating (FBG) temperature sensors embedded in PMSM windings to enable winding open circuit fault diagnosis based on observing the fault thermal signature. Final element analysis (FEA) thermal and electromagnetic models of the examined practical PMSM design are first developed and used to enable understanding of open circuit winding fault induced signature that can be used for effective diagnostic purposes, indicating in-situ thermal excitation as an optimal diagnostic measurand. A purpose build test rig with an inverter driven commercial PMSM instrumented with in-situ FBG sensors monitoring phase winding hot spots is then used to evaluate the efficacy of the proposed diagnostic scheme. It is shown that unambiguous diagnosis and severity trending of winding open circuit faults is enabled by use of in-situ FBG sensors. A comparison with conventional fault diagnostic technique utilising current signal sensing and analysis is also reported, indicating considerable advantages of the proposed monitoring scheme employing FBG sensors.