this study proposes a magnetic sensor design and application for monitoring the health of rotor magnets in permanent magnet (PM) electrical machines through in-situ observation of the air-gap magnetic flux density. The reported device employs the concept of Fibre Bragg Grating (FBG) strain sensing fusion with magnetostrictive material to deliver a machine stator slot wedge integrated sensor that allows straightforward installation and retrofit with no invasive action to core elements of the machine. The sensing theory, design, prototyping, calibration and installation of the proposed magnetic sensing scheme are detailed in the paper. The sensor was installed into an inverter driven surface mount PM synchronous machine (SPMSM) and its performance for in-situ observation of rotor PM magnetization conditions validated in a range of healthy and demagnetised PM conditions tests. The obtained experimental data demonstrate the reported device's capability to enable recognition of rotor PMs' magnetisation level and thus their health monitoring. Finally, a fault index is proposed and experimentally validated that allows the application of in-situ magnetic sensor measurements for relative quantification of PM demagnetization fault severity.

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Winding short circuit faults are recognized as one of most frequent electric machine failure modes. Effective on-line diagnosis of these is vital, but remains a challenging task, in particular, at incipient fault stage. This paper reports a novel technique for on-line detection of incipient stator short circuit faults in random wound electrical machines based on in situ monitoring of windings thermal signature using electrically nonconductive and electromagnetic interference immune fiber-Bragg grating (FBG) temperature sensors. The presented method employs distributed thermal monitoring, based on the FBG multiplexing feature, in a variety of points within windings, in proximity to thermal hot spots of interest that arise from fault. The ability of the proposed method to enable fault diagnosis through identification of fault-induced localized thermal excitation is validated in steady-state and transient operating conditions on a purpose built inverter driven induction machine test facility. The results demonstrate the capability of unambiguous detection of inter-turn faults, including a single shorted turn. Furthermore, the winding thermal and electrical characteristics at the onset of inter-turn fault are examined and correlated, enabling better understanding of fault diagnostic requirements. Index Terms-Fiber-Bragg grating (FBG) sensor, insitu thermal monitoring, inter-turn fault detection, inverter driven induction motor.

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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.

Miniature Circuit Breakers (MCB) are protective devices used in low voltage applications. To perform their protection function, MCB contain two different trip systems: a thermal unit and an electromagnetic unit. Current thermal trip unit designs were introduced decades ago and are based on bimetal technology. This paper introduces a new technology based on compliant mechanisms that replaces bimetals in MCB.The proposed architecture uses a thermosensitive compliant mechanism whose design is calibrated to perform as traditional bimetal designs do, but with the advantage of reduced heat losses. An additional advantage of the new design is its monolithic construction, which reduces the number of parts in the MCB. The design of an MCB equipped with this technology is presented. Basic sizing equations for design purposes are introduced. The performance of the thermal trip unit is analyzed using finite element analysis (FEA) models, with special attention paid to the protective function and thermal losses of the new design. Lab experiments with prototypes are also presented. Results indicate that the performance of the proposed design is similar to the bimetal technology it replaces, with reduced power losses. Index Terms-Circuit Breakers, Numerical Simulation, Finite element analysis, Mathematical modelI. 0093-9994 (c)

This paper reports an experimental study aimed at characterising the response of an in-situ fibre optic fibre Bragg grating / magnetostrictive flux sensor when exposed to excitation in orientations aligned with and perpendicular to its optimal performance axes. The study is aimed at improving the understanding of the potential for non-invasive in-situ application of this sensing technology in devices with confined geometries which impose restrictions on possible magnetic excitation axis alignment with that of the sensor, such as those encountered in rotating electric machinery.

Using robotic systems to conduct remote inspections of offshore wind farm HVDC converter stations has been proposed as a promising solution to reduce the operation and maintenance (O&M) down-time and costs. However, the nature of the electromagnetic field environment inside HVDC valve halls presents a challenge for the operation of traditional off-shelf inspection robots. High electrostatic interference to inspection unmanned aerial vehicles (UAV) has been studied in Part A of this paper. In Part B, the impact of the external magnetic field on the operation of an inspection quadcopter‘s propulsion motors is assessed. An experimental method is proposed to identify the maximum magnetic field tolerable by off-the-shelf quadcopter motors. The reported method can be used to test commercial off-the-shelf quadcopter motors to identify their suitability for use in HVDC valve halls inspection robots. The paper experimental results show the failure of direct torque control (DTC) algorithm, that is used in quadcopters speed controllers in mitigating the magnetic field impact on motor‘s speed and current consumption.