Investigation of Using Fibre Bragg Grating Sensing Technology for Thermal Condition Monitoring In Electric Machinery

Abstract

This thesis reports an investigation of the design, development, implementation and use of in-situ thermal sensing systems utilising Fibre Bragg Grating Sensing Technology (FBGST) for low voltage electric machine (LVEM) thermal condition monitoring applications. The thesis first investigated the key design and operational features of the in-situ FBG temperature sensor for thermal hot spot monitoring in stand-alone prototype random wound components. Vital sensing aspects such as the sensor characterisation, packaging material choice, in-situ calibration requirements, use of multiplexing for distributed sensing, the installation procedure and the thermal measurement sensitivity to machine vibration were investigated. The reported findings enable a much improved understanding of the performance implications of embedded FBG sensor design features and the attainable in-situ hot spot thermal monitoring performance in random wound coils. It is shown that reliable, improved fidelity information on the coil’s thermal status can be obtained from application of wound coil embedded FBG thermal sensing systems. The thesis then reported the use and performance evaluation of the devised in-situ FBG temperature sensor in operational LVEMs. Different in-situ FBG thermal sensing configurations were designed and embedded into two standard LVEM topologies: an induction machine and a permanent-magnet synchronous machine. The in-situ system’s on-line thermal monitoring performance was experimentally examined under different thermal conditions, ranging from typical healthy continuous and periodic running duty cycles, to a deteriorated cooling system and winding fault conditions. It was demonstrated that the presented scheme has the potential to provide competent on-line measurement of critical machine thermal hot spots that are largely beyond effective reach of conventional thermal monitoring solutions. In addition, the ability of the proposed system to enable fault diagnosis through identification of fault induced localised thermal signature is also reported. The results demonstrate the capability of unambiguous recognition of inter-turn faults, including a single shorted turn, and diagnosis of fault severity, location and fault critical-thermal operating conditions. Finally, the winding thermal and electrical characteristics at inter-turn fault onset were investigated, enabling advanced understanding of fault thermal signature manifestation in a wide range of operating conditions. The thesis also investigated the use of the FBGST multi-physical sensing feature for extracting simultaneous thermal and mechanical information of rotary components for condition monitoring purposes. It is shown that a single FBG embedded in a bearing or rotor structure can enable simultaneous understanding of component’s thermal and mechanical operating conditions, and thus improved understanding of their health status.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alexander Smith (Supervisor) & Sinisa Durovic (Supervisor)