Fillet Radius Impact of Rectangular Insulated Wires on PDIV for Turn-to-Turn Insulation of Inverter-Fed Motors

This contribution elucidates the impact of the fillet radius, a geometric feature of rectangular insulated wires not commonly considered, on the partial discharge inception voltage (PDIV) in low-voltage machine turn-to-turn winding insulation. Initial PDIV tests involve edgewise-insulated wire samples with a reference fillet radius. These measurements are performed under constant conditions: 30°C temperature, 35% relative humidity, and atmospheric pressure (1000 mbar). These tests are carried out under AC 50 Hz excitations, following IEC 60034-18-41 guidelines for inverter-fed motor insulation system qualification. Subsequently, a probabilistic PDIV predictive model is developed based on Schumann’s streamer inception criterion (SCSIC). This expanded model then analyses and forecasts the impact of the fillet radius on PDIV and its associated dispersion level, within the context of the 2-parameter Weibull distribution and the given environmental conditions. Furthermore, a novel method is presented to understand partial discharge (PD) phenomenology and its destructive potential in rectangular insulated wires with varying fillet radii. This approach employs SCSIC-derived streamer inception parameters (SIPs): critical field line length (CFLL), air effective ionization coefficient (α_eff), PD inception field (Einc), and firing voltage (Vfiring). The developed probabilistic predictive model enables the selection of an optimal fillet radius value, facilitating the creation of a reliable insulation system with maximum PDIV and minimal PD-related damage

Celebrating five years of innovative care in the community

The Eating Disorder Project (EDP) started as a one-year pilot project, commissioned by local GPs in a borough of London in January 2016.The idea actually sprouted when Miranda Boal now the service lead, left her post in a secondary care eating disorders service to help set something up in the community.Dr Martina Gerada tells us more

Novel integrative options for passive filter inductor in high speed AC drives

This paper presents novel integration options for passive inductor which include: motor-shaped rotational and motor-shaped rotor-less inductor for high speed motor drive system. The novel options have been designed and their performance is compared with the conventional EE core inductor using finite element analysis. It is observed that there is a significant reduction in total losses at fundamental frequency along with substantial reduction in the AC copper loss at 10, 15 and 20 kHz switching frequencies, when the proposed integrated options are utilized. For the motor-shaped rotational inductor, the total losses at fundamental frequency and AC copper loss at different switching frequencies are reduced by 26.1% and 73.8% (at different switching frequencies) respectively. There is a reduction in overall volume by 3.6%, but this comes with 11.7% increase in weight. For the motor-shaped rotor-less inductor, the total losses at fundamental frequency and AC copper loss at different switching frequencies are reduced by 10.4% and 73.8% (at different switching frequencies) respectively. There is a reduction in overall volume by 3.6% but this comes with 6.1% increase in weight. The proposed designs can share the cooling system of the motor thus, eliminating the requirement of separate cooling system

Design optimization of integrated rotational inductor for high-speed AC drive applications

In order to make an efficient and power dense overall system, a close physical and functional integration of passive components is required instead of having a separate sub¬system for passives. Such power dense system is vital in aerospace and marine applications. This paper presents the design optimization of integrated rotational inductors for high speed AC drive applications. Design degrees of freedom like slot-pole combinations along with different winding configurations such as, single layer (SL), double layer (DL), concentrated winding (CW) and distributed winding (DW) are considered. In this paper, the rotational inductors are optimized for these degrees of freedom and compared with a benchmark EE core inductor in terms of total losses, weight and AC copper resistance at both fundamental frequency (1 kHz) and switching frequency (10, 15 and 20 kHz). The comparative analysis between EE core and rotational inductors has shown a significant reduction in total losses and AC copper resistance at fundamental frequency and all switching frequencies. In comparison with EE core inductor, 12 slots 2 poles rotational inductor with SL DW gives lowest total losses at fundamental frequency whereas 6 slots 2 poles rotational inductor with SL DW offers the lowest AC copper resistance at both fundamental and all switching frequencies

Comprehensive monitoring of electrical machine parameters using an integrated fibre Bragg grating-based sensor system

In this paper a multi-parameter, multi-sensor system for comprehensive electrical machine condition monitoring has been developed and the results of an evaluation reported. The FBG-based system developed allows for the simultaneous monitoring of key parameters including machine vibration, rotor speed and position, torque, spin direction, temperature distribution along the stator windings and on the rotor surface as well as the stator wave frequency. This all-optical sensing solution has been designed to be compatible with being fitted in the tight confines of an electric motor and uses the optical nature of the measurement and the insulating nature of the sensor material to avoid problems of electrical interference. The system reduces the component count over conventional sensor systems, i.e., all sensing elements are contained within the machine and operated by a single sensing interrogation unit, thereby reducing cost and allowing for a convenient interface for the user. The design of the system is presented, as are results on the testing and evaluation of the device the sensing system has been successfully integrated into and tested on a permanent magnet motor prototype

Multi-parameter monitoring of electrical machines using integrated fibre Bragg gratings

In this paper a sensor system for multi-parameter electrical machine condition monitoring is reported. The proposed FBG-based system allows for the simultaneous monitoring of machine vibration, rotor speed and position, torque, spinning direction, temperature distribution along the stator windings and on the rotor surface as well as the stator wave frequency. This all-optical sensing solution reduces the component count of conventional sensor systems, i.e., all 48 sensing elements are contained within the machine operated by a single sensing interrogation unit. In this work, the sensing system has been successfully integrated into and tested on a permanent magnet motor prototype

AC losses reduction in Hairpin Windings produced via Additive Manufacturing

One of the key challenges of hairpin windings is the reduction of their high losses at high-frequency operations. Hairpin layouts comprising conductors with variable cross sections have proven good loss performance in previous studies. However, they come at the cost of significant manufacturing complications. The aim of this work is to design hairpin layouts featuring reduced losses compared to classical configurations, exploiting the flexibility enabled by additive manufacturing. In this context, the choice of a proper material with relatively high conductivity and low ecological impact plays an important role. Hence, this article first presents an overview of materials that can be used for the winding additive manufacturing, aiming to select the most suitable one for the application at hand. Then, the loss performance is evaluated and compared against classical copper hairpins. The results demonstrate that opportunely selected alloys featuring asymmetric configurations can compete against classical hairpin windings. © 20XX IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper reflects only the author's view. JU is not responsible for any use that may be made of the information it contains

Modifications to PM-assisted Synchronous Reluctance Machine to Achieve Rare-Earth Free Heavy-duty Traction

Automotive applications require electrical machines designed for high torque density, wide speed range, and low cost. NdFeB magnets can achieve a high torque density and wide speed range, and however, they have a high cost. Therefore, this article explores the capability of rare-earth-free (REF) design through a PM-assisted synchronous reluctance (PM-SynRel) motor. A PM-SynRel design with NdFeB has been used in this study where the NdFeB magnets have been replaced with ferrite magnets. Then, several modifications on the rotor have been made to ensure mechanical safety. Thermal analysis has been conducted last to evaluate the temperatures in the different machine parts to avoid exceeding the required limits. Finally, a prototype has been made and tested to validate the simulation results

Diagnostic value of transvaginal 'tenderness-guided' ultrasonography for the prediction of location of deep endometriosis

BACKGROUND: The aim was to evaluate the diagnostic accuracy of transvaginal tenderness-guided ultrasonography in the identification of location of deep endometriosis. METHODS: Consecutive women scheduled for surgery in our Department for clinically suspected endometriosis were included in this prospective study. All women underwent modified transvaginal ultrasonography using a stand-off in the week before surgery, which also evaluated the painful sites evocated by a gentle pressure of the probe. Five locations of deep endometriosis were considered: vaginal walls, rectovaginal septum, rectosigmoid involvement, uterosacral ligaments and anterior compartment (anterior pouch and/or bladder). Sensitivity, specificity and likelihood ratios (LR1/2) were calculated with 95% confidence intervals (CIs). RESULTS: We included 88 women; surgery associated with histopathological evaluation revealed deep endometriosis in different pelvic locations in 72 patients. With respect to the vaginal walls, transvaginal ultrasonography had a sensitivity of 91% (95% CI, 79 –97%), specificity of 89% (95% CI, 81–93%), an LR1 of 8.2 and an LR2 of 0.09. For endometriosis of rectovaginal septum, transvaginal ultrasonography had a sensitivity of 74% (95% CI, 64–80%), specificity of 88% (95% CI, 4–8%), an LR1 of 6.2 and an LR2 of 0.3. For other locations, the sensitivity was lower (ranging from 67% to 33%) with a comparable specificity. CONCLUSIONS: This technique shows a high specificity and sensitivity in the detection of vaginal and rectovaginal endometriosis. Good specificity associated with a lower sensitivity was obtained in the diagnosis of deep endometriosis of uterosacral ligaments, rectosigmoid involvement or anterior deep endometriosis

Assessment of Edgewise Insulated Wire Bend Radius Impact on Dielectric Properties of Turn-to-Turn Insulation through Thermal Ageing

This study aims to evaluate the impact of the bending radius of edgewise insulated wires on dielectric properties such as partial discharge inception voltage (PDIV), partial discharge extinction voltage (PDEV), dielectric dissipation factor (DDF), and insulation capacitance (IC) through thermal ageing. The tests are performed at room temperature (20°C) and atmospheric pressure (1013 mbar) on unaged and thermally aged polytetrafluoroethylene (PTFE)-wrapped pairs of edgewise insulated wires, models of the turn-to-turn insulation. The accelerated thermal ageing is carried out at 250°C (i.e., 50°C higher than thermal class) for two different ageing periods: 156 and 312 hours. To manufacture a coil, it is generally demanded to shape 90-degree bends out of edgewise enamelled winding wires. Therefore, the obtained experimental results are helpful for the coil manufacturers, providing a clue how the bending radius can impact the dielectric properties of turn-to-turn insulation and introducing an optimum radius which can present better insulation performance