Abstract
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 fiber Bragg grating (FBG) temperature sensors embedded in PMSM windings to enable winding open-circuit fault diagnosis based on observing the fault thermal signature. The final element analysis thermal and electromagnetic models of the examined practical PMSM design are first developed and used to enable the 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 the use of in situ FBG sensors. A comparison with conventional fault diagnostic technique utilizing current signal sensing and analysis is also reported, indicating the considerable advantages of the proposed monitoring scheme employing FBG sensors.
Highlights
P ERMANENT Magnet Synchronous Machines (PMSMs) are key elements of a number of contemporary industrial systems, ranging from application as preferred propulsion motor choice in modern electric vehicles (EVs) to being enabling components of military, medical, factory automation, aerospace and wind energy systems [1], [2]
The discrepancy between the in-situ hot spot temperature rise sensed values (Fig. 10) and those predicted by finite element analysis (FEA) thermal study (Table II) is because the FEA simulated fault condition temperatures are for thermal steady-state conditions, while in practical fault experiments the temperature was recorded only for a 60 seconds period for winding protection purpose, due to the potentially destructive nature of the emulated fault if allowed to propagate towards fault thermal steady-state
The presented current measurements further illustrate the importance of ensuring provision of an effective stranded winding PMSM open circuit (OC) fault diagnosis system: conventional phase current based PMSM protection systems will not react to this type of fault, since there is no significant change in the phase current to provide a trip warning for the protection system
Summary
P ERMANENT Magnet Synchronous Machines (PMSMs) are key elements of a number of contemporary industrial systems, ranging from application as preferred propulsion motor choice in modern electric vehicles (EVs) to being enabling components of military, medical, factory automation, aerospace and wind energy systems [1], [2]. Advanced on-line thermal monitoring use for stator winding fault diagnosis has not been widely investigated [20], [21] This is due to operational limitations of conventional thermal sensing techniques used in electric machines, in timely, reliably and effectively accessing and measuring the fault induced thermal signature (i.e. localized hot-spots) within the winding structure. To facilitate the understanding of sensing requirements for effective OC fault signature recognition, this section undertakes a multi-physical FEA model analysis of OC fault electrical and thermal characteristics of a commercial stranded winding PMSM design examined in this work This allows the possible and optimal measurands associated with OC fault presence to be identified and the requirements for their sensing and monitoring to be defined. This illustrates the challenge of detecting this fault type in PMSMs using the current signature monitoring method
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