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A green revolution has accelerated over the recent decades with a look to replace existing transportation power solutions through the adoption of greener electrical alternatives. In parallel the digitisation of manufacturing has enabled progress in the tracking and traceability of processes and improvements in fault detection and classification. This paper explores electrical machine manufacture and the challenges faced in identifying failures modes during this life cycle through the demonstration of state-of-the-art machine vision methods for the classification of electrical coil winding defects. We demonstrate how recent generative adversarial networks can be used to augment training of these models to further improve their accuracy for this challenging task. Our approach utilises pre-processing and dimensionality reduction to boost performance of the model from a standard convolutional neural network (CNN) leading to a significant increase in accuracy.

Different from traditional EM coil launcher, a new type of primary construction was brought forward in this paper. The energy storage capacitor and primary winding were integrated into one component. The relevant basic equations of mathematical physics were deduced, the finite element simulation was carried out, and the experimental principle prototype was set up for experimental verification, which proves that the new structure is expected to enable the development of more compact and more efficiency EM coil launcher.

With an aim to develop a good coil winding insulation film, fillers of boehmite alumina in the shape of a roughly rectangular plate were added with ratios of 10 and 20 wt% to polyimide. The filler surface was untreated or treated with a methacrylic or an epoxy silane coupling agent. Such prepared polyimide nanocomposites were subjected to various tests to measure the tensile strength, elastic modulus, complex permittivity, and thermal conductivity. It was found that samples with fillers treated using the methacrylic silane coupling agent have the strongest adhesion at the filler/polyimide interfaces and the lowest dielectric loss factor at high temperatures. A positive relationship between the filler/polyimide adhesion and the thermal conductivity is also indicated. These findings are significant since they indicate that the adhesion status at the filler/polymer interface exerts a strong influence on the thermal and electrical conduction processes in the polymer.

Recently, unmanned aerial vehicles (UAVs) based on electric propulsion systems are being increasingly adopted in various fields, including industrial and military applications. Outer-rotor surface-mounted permanent magnet synchronous motors (SPMSMs) are predominantly applied in UAV propulsion systems. However, these motors are vulnerable to the price fluctuations of rare-earth materials and supply chain instability. In addition, the magnets in these motors are prone to detachment at high rotational speeds, and demagnetization under high-temperature conditions may reduce output performance. To address these limitations, research is being actively conducted on non-permanent magnet motors, among which, wound-rotor synchronous motors (WRSMs) offer the advantage of controllable field excitation at high speeds. Furthermore, WRSMs can use both magnetic and reluctance torques, thereby increasing power density relative to other non-permanent magnet motors. However, the adoption of an additional field winding increases copper loss, thus reducing motor efficiency. This study investigates the application of the toroidal winding structure, which is already widely applied in permanent magnet and brushless direct current machines, to WRSMs. The performance of these motors is compared with that of motors using conventional tooth-coil windings. The toroidal windings are circumferentially distributed along both the inner and outer stator yoke paths, effectively reducing the end-turn length relative to that of conventional tooth-coil windings. Two WRSMs, one with tooth-coil and another with toroidal windings, are designed using identical specifications to compare performances via finite element analysis. The armature copper loss in the proposed model decreased by approximately 28% because the toroidal winding structure reduced the end-turn length. As a result, the efficiency increased by about 1.9% due to the reductions in copper, core, and eddy current losses.

The recently discovered non-Hermitian skin effect (NHSE) manifests the breakdown of current classification of topological phases in energy-nonconservative systems, and necessitates the introduction of non-Hermitian band topology. So far, all NHSE observations are based on one type of non-Hermitian band topology, in which the complex energy spectrum winds along a closed loop. As recently characterized along a synthetic dimension on a photonic platform, non-Hermitian band topology can exhibit almost arbitrary windings in momentum space, but their actual phenomena in real physical systems remain unclear. Here, we report the experimental realization of NHSE in a one-dimensional (1D) non-reciprocal acoustic crystal. With direct acoustic measurement, we demonstrate that a twisted winding, whose topology consists of two oppositely oriented loops in contact rather than a single loop, will dramatically change the NHSE, following previous predictions of unique features such as the bipolar localization and the Bloch point for a Bloch-wave-like extended state. This work reveals previously unnoticed features of NHSE, and provides the observation of physical phenomena originating from complex non-Hermitian winding topology. Non-Hermitian skin effect fundamentally challenges the conventional topological description of a system. Here the authors demonstrate a bipolar non-Hermitian skin effect, where bulk eigenstates localize towards two directions, in a one-dimensional non-reciprocal acoustic crystal with twisted topology.

PurposeThe aim of this paper is to provide a simple yet accurate and efficient geometric method for thermal homogenization of impregnated and non-impregnated coil winding technologies based on the concept of thermal resistance.Design/methodology/approachFor regular windings, the periodic microscopic cell in the winding space is identified. Also, for irregular windings, the average microscopic cell of the winding is determined. An approximation is used to calculate the thermal resistance of the winding cell. Based on this approximation, the winding insulation is considered as a circular ring around the wire. Mathematical equations are obtained to calculate the equivalent thermal resistance of the cell. The equivalent thermal conductivity of the winding is calculated using equivalent thermal resistance of the cell. Winding thermal homogenization is completed by determining the equivalent thermal properties of the cell.FindingsThe thermal pattern of different windings is simulated and compared with the results of different homogenization methods. The results show that the proposed method is applicable for a wide range of windings in terms of winding scheme, packing factor and winding insulation. Also, the results show that the proposed method is more accurate than other winding homogenization methods in calculating the equivalent thermal conductivity of the winding.Research limitations/implicationsIn this paper, the change of electrical resistance of the winding with temperature and thermal contact between the sub-components are ignored. Also, liquid insulators, such as oils, and rectangular wires were not investigated. Research in these topics is considered as future work.Originality/valueUnlike other homogenization methods, the proposed method can be applied to non-impregnated and irregular windings. Also, compared to other homogenization methods, the proposed method has a simpler formulation that makes it easier to program and implement. All of these indicate the efficiency of the proposed method in the thermal analysis of the winding.

Due to their compact dimensions, high torque density, high efficiency, and superior flux-weakening capabilities, permanent magnet synchronous machines with tooth-coil winding (TC-PMSMs) are highly suitable for low-power electric transportation applications. This study incorporates the actual duty cycle of an electric motorcycle in the optimization of the slot number for the drive machine. The proposed methodology addresses the shortcomings of conventional design strategies, which typically consider only a limited set of operating points, leading to suboptimal round-trip efficiency under real driving conditions. Firstly, the influence of slot number on torque output, electromagnetic losses, and flux-weakening performance is examined for 10-pole TC-PMSMs using finite element analysis. Subsequently, the optimal slot number is identified by integrating the real duty cycle of the drive motor into the evaluation. To verify the accuracy and effectiveness of the analytical results and design approach, prototypes of stator assemblies with varying slot numbers were fabricated and experimentally tested.

Multiturn coils are required for manufacturing sheet metal parts with varying depths and special geometrical features using electromagnetic forming (EMF). Due to close coil turns, the physical phenomena of the proximity effect and Lorentz forces between the parallel coil windings are observed. This work attempts to investigate the mechanical consequences of these phenomena using numerical and experimental methods. A numerical model was developed in LS-DYNA. It was validated using experimental post-mortem strain and laser-based velocity measurements after and during the experiments, respectively. It was observed that the proximity effect in the parallel conductors led to current density localization at the closest or furthest ends of the conductor cross-section and high local curvature of the formed sheet. Further analysis of the forces between two coil windings explained the departure from the “inverse-distance” rule observed in the literature. Finally, some measures to prevent or reduce undesired coil deformation are provided.

Purpose The difficulty in winding coil-based electrical and electronic devices manually lies in the fact that it takes so much time and effort to perform. Furthermore, it is difficult to achieve accuracy manually, as it is possible to lose count of the number of turns being wound. The purpose of this paper is to detail the design methods and calculations used to achieve a cost-effective, significantly accurate and more efficient method of winding coils. Design/methodology/approach A program flowchart was designed as a guideline for writing the program. An AT89C52 microcontroller was used to control the movement of the two direct current (DC) motors used in the construction of the machine. The circuit design obtained was then simulated using Proteus to test the functionality of the components together. Findings An electromechanical automatic coil winding machine for the coiling of simple, small-sized, coil-based electrical devices was successfully designed and fabricated. The machine was tested by winding a 1 kVA transformer. Diagrams, calculations, results and observations obtained during the design and construction are detailed in this paper. Originality/value This machine solves the problem of tediousness in coil winding, stably and precisely winding 60 turns/min at a 24 V supply and providing a keypad input method. Although portable automatic coil winding machines have been rendered previously, most have applied the use of stepper motors. The application of brushed DC motors alongside an AT89C52 microcontroller is a variation to the pool of renditions, offering better controllability and a sustained output.

This paper analyzes the impact of manufacturing tolerances on the cogging torque of a 24-slot 28-pole tooth-coil-winding permanent magnet synchronous machine with a modular stator core (TCW-MPMSM). Dimensional tolerances and asymmetries associated with the modular topology are studied by means of finite element simulations in order to identify key parameters that increase the cogging torque above the expected values of a faultless machine. Among five selected dimensional parameters, it was found that angular displacement, radial displacement, and tooth–tip width deviations of the stator segments have the most significant impact on the cogging torque. Considering these three key parameters, a full-range tolerance analysis is carried out by means of a proposed superposition-based approach, evaluating all possible combinations of typical deviation values. It is concluded that the cogging torque increment, generated by tolerances, is relatively independent of the faultless tooth–tip width of the stator segments and the arc-to-pole ratio. Robustness of the TCW-MPMSM, regarding cogging torque generation, depends on both the tightness of the tolerances handled in the manufacturing process and the rated cogging torque: the lower the cogging torque of the ideal machine, the less robust is the machine and, therefore, manufacturing imperfections will be required to be tightened.