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This paper is devoted to the shape optimization of the internal structure of an electric motor, and more precisely of the arrangement of air and ferromagnetic material inside the rotor part with the aim to increase the torque of the machine. The governing physical problem is the time-dependent, nonlinear magneto-quasi-static version of Maxwell's equations. This multiphase problem can be reformulated on a 2D section of the real cylindrical 3D configuration; however, due to the rotation of the machine, the geometry of the various material phases at play (the ferromagnetic material, the permanent magnets, air, etc.) undergoes a prescribed motion over the considered time period. This original setting raises a number of issues. From the theoretical viewpoint, we prove the well-posedness of this unusual nonlinear evolution problem featuring a moving geometry. We then calculate the shape derivative of a performance criterion depending on the shape of the ferromagnetic phase via the corresponding magneto-quasi-static potential. Our numerical frameworkto address this problem is based on a shape gradient algorithm. The nonlinear time periodic evolution problems for the magneto-quasi-static potential is solved in the time domain, with a Newton–Raphson method. The discretization features a space-time finite element method, applied on a precise, meshed representation of the space-time region of interest, which encloses a body-fitted representation of the various material phases of the motor at all the considered stages of the time period. After appraising the efficiency of our numerical framework on an academic problem, we present a quite realistic example of optimal design of the ferromagnetic phase of the rotor of an electric machine. [ABSTRACT FROM AUTHOR]

This study aimed to improve small-scale cabbage harvesting, which usually depends on labour-intensive methods. To solve this issue, an electric cabbage harvester for single-row applications was designed and developed. The harvester integrates different units, such as cutting, conveying, precise cabbage pushing, propelling, power supply (lead acid batteries), storage bin, and handle. The study involved selecting appropriate driving motors, optimising transmission in each unit, and designing the power supply. Critical components, including the cutter, pusher, and propelling shafts, were designed and subjected to static and dynamic analysis using ANSYS R18.0. In the static analysis torque values of 27.52 Nm, 40.99 Nm, and 888.35 Nm were used for the cutter, pusher, and propelling shafts, respectively, with dynamic analysis assuming peak torques 1.5 times higher. Maximum equilibrium stresses in the static analysis were 14.20 MPa, 7.35 MPa, and 36.36 MPa, while the dynamic analysis recorded 22.996 MPa, 9.145 MPa, and 66.88 MPa, all below the material's yield stress. The results confirmed the safety and reliability of these components during field operations. A 2571 × 880 × 742 mm prototype was developed, with hand vibration and noise levels measured at 2.098 m/s2 and 78 dB(A), ensuring ergonomic safety. The harvester presents a promising solution for mechanising small-scale cabbage harvesting. [ABSTRACT FROM AUTHOR]

Helical milling is widely used in aerospace as a key processing technology for Carbon fiber reinforced polymer (CFRP). However, the eccentric machining characteristics lead to an unusually complex pattern of cutting force and residual stress distribution on the work-piece during helical milling processing. Based on the Hashin failure criterion, a 3D FEM model of CFRP helical milling was built for analyzing the changing law of cutting force, then the three factors and three levels orthogonal tests were used to investigate the influence of machining parameters on the axial force, radial force, and minimum principal residual stress, finally, the multi-objective optimization based on grey correlation analysis was realized. The results showed that the errors of axial force and radial force obtained by simulation and experiment were 10.68% and 12.26%, respectively. The axial force and radial force were negatively correlated to the spindle speed, positively correlated to the axial cutting depth, and uncorrelated to the feed per tooth. The minimum principal residual stress was negatively correlated to the spindle speed, positively correlated to the feed per tooth, and uncorrelated to the axial cutting depth. The degree of influence on optimization of machining parameters was: spindle speed > axial cutting depth > feed per tooth. The corresponding average grey correlation degree differences were 0.280981, 0.216859, and 0.013422, respectively. The maximum value of grey correlation degree in the orthogonal test was 0.874372, and the corresponding optimal parameters combination was the spindle speed 8000 r/min, feed per tooth 0.03 mm/z, and axial cutting depth 0.2 mm/r. [ABSTRACT FROM AUTHOR]

This paper describes the detailed design procedure of electric machines using finite element analysis (FEA). The proposed method uses the available findings from the literature and FEA results for the design procedure. In addition to electromagnetic analysis, thermal analysis is executed to examine the capability of the designed machines for handling the load in terms of thermal limits. It allows for considering the normal and overload performance of the electric machines during design. The proposed design procedure is used for designing a 100 kW induction machine (IM) and interior permanent magnet synchronous machine (IPMSM) for a parallel hybrid electric vehicle (HEV). The differences between the performance parameters of the studied machines are discussed, and the advantages and disadvantages of each design are highlighted. The designed machines are compared with commercially available electrical machines in terms of performance and power density. The comparison demonstrates that the developed machines can offer comparable performance to other designs. [ABSTRACT FROM AUTHOR]

This paper presents a method aimed at improving comprehension of AC electric machine principles by facilitating the learning of the Rotating Magnetic Field (RMF) through visualization tools provided by Finite Element Method (FEM) software. First, traditional methods used in textbooks to explain RMF in electric machines are reviewed, with an analysis of various instructional strategies. Acknowledging the limitations of these conventional approaches and the inherent complexity of RMF comprehension, a novel visualization method is proposed. Understanding RMFs in electric machines is fundamental for electrical engineers due to their crucial role in electric machine design and optimization. While textbooks typically rely on mathematical explanations and simple sketches, advancements in computer and software technology offer opportunities to utilize finite element tools for enhanced comprehension. Through dynamic animations and interactive simulations, emphasis is placed on prioritizing conceptual understanding over mathematical descriptions. Furthermore, this paper explores the development of pre‐simulation models in FEM tools to facilitate RMF learning in AC electric machines, and the process of creating a model to teach rotating magnetic fields in electric machines is carefully outlined. This approach holds promise for engineers seeking a deeper understanding of electric machines and can also be utilized by educators to enhance their teaching methodologies. [ABSTRACT FROM AUTHOR]

The authors propose an analytical modelling approach for the linear transverse flux permanent magnet motor using the magnetic equivalent circuit method. The main focus of this study is to predict the phase flux‐linkage characteristic of the motor. Essential equations required for implementation of the model and how to solve it are described clearly so that someone can use it easily. A typical motor is selected to apply the proposed model and simulation results, including static characteristics of flux‐linkage and thrust, are presented. To validate the developed analytical model, the discussed motor is also analysed with 3D finite element method using MAXWELL software and the obtained simulation results are compared to each other. [ABSTRACT FROM AUTHOR]

The paper presents the results of research on the spatial distribution of the multi-phase, distributed windings in electric machines. The focus was on the analysis of the harmonics of the current linkage spatial distributions. To perform calculations for different windings patterns, taking into account the number of phases, pole pairs, and the number q of slots per pole and phase, the dedicated code was developed in the Matlab environment. Nine different multi-phase windings were studied, for which magnetomotive force (MMF) was determined to investigate the harmonic content and total harmonic distortion. The obtained results were compared with a reference three-phase symmetric system. Studies were also carried out on torque ripple and power density for different numbers of winding phases. [ABSTRACT FROM AUTHOR]

The authors present two fast and accurate methodologies for the computation of eddy current losses in the axially laminated rotor of a synchronous reluctance machine. The methodologies are based on different combinations of the finite element method in time and frequency domains with 2D and 3D formulations. First, a comparative study of the 2D and 3D formulations for loss calculation is presented, considering various load angles of the machine to illustrate the problem of eddy‐current losses in this type of machines and its dependence on the load angle. The influence of the iron saturation on the loss calculation is also evaluated in these computations. A novel correction factor based on the computations at two load angles is proposed to convert the losses computed from a 2D model to match those computed from a 3D model. For the sake of generality, investigations are also conducted for various thicknesses of the lamination layers and different machine lengths, and an analytical method to describe the dependency of eddy‐current losses on the load angle of the machine is introduced. Moreover, a simplified method is proposed for modelling eddy currents in the frequency domain and calculating losses in an axially laminated structure based solely on the results of a magnetostatic solution. The results obtained by the simplified model demonstrate excellent agreement with the full 3D magneto‐dynamic simulation. Overall, the findings contribute to understanding and accurately characterising the eddy current losses in axially laminated rotors, offering potential insights for designing and optimising axially laminated synchronous reluctance electric machines. [ABSTRACT FROM AUTHOR]

This paper presents a thermal analysis of a switched reluctance machine (SRM) with a 6/4 pole topology. Employing a two-dimensional thermal finite element model in Maxwell 2D integrated into a lumped parameter thermal network in MotorCAD, the research aims to realize critical temperature points within the SRM, focusing on the windings and laminations to identify potential hotspots. To ensure continuous operation without compromising structural integrity, temperature constraints of 150 °C for the windings and 100 °C for the laminations were enforced. The investigation extends to the cooling domain by utilizing a housing cooling jacket and ethylene glycol and water ratio (EGW) of 60/40 as the cooling fluid. An exploration of various volume flow rates revealed that 15 l/min was the optimal choice, resulting in the lowest temperatures observed in both the winding and lamination regions. This study emphasizes the shift of hotspot temperatures from the stator winding in the low-speed region to the rotor in the high-speed range, impacting the overall continuous operating time. This holistic examination significantly contributes to a broader understanding of electric machine thermal management and offers invaluable insights for practical applications in electric vehicles, manufacturing processes, and various industrial settings. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of corrosion on the magnetic circuit's influence on the induction machine's magnetic characteristics. To achieve this objective, we initially evaluated the magnetic properties of the induction machine's magnetic circuit under both corroded and non-corroded conditions by analyzing hysteresis loops using a vibrating sample magnetometer. We systematically examined magnetic parameters extracted from these experiments, including saturation magnetic flux density, coercive field, remanence, and the squareness ratio. Subsequently, we employed the finite element method to scrutinize the magnetic behavior of the induction machine under both corroded and non-corroded conditions. The magnetic parameters obtained from the experiments were then incorporated into the model representing the induction machine's magnetic circuit. The results demonstrate that corrosion in the magnetic circuit significantly impacts the induction machine's magnetic behavior, ultimately leading to reduced machine efficiency. [ABSTRACT FROM AUTHOR]

As one sort of flux modulation machine based on magnetic gear effect, field-modulated machine features with low speed large torque. A novel hybrid excitation field-modulated machine (HEFMM) is proposed by introducing the concept of hybrid excitation, the flux modulation poles (FMPs) and excitation winding of which are emplaced in stator teeth and the adjacent FMPs. It can be maintained wide speed range operation through the processes of flux-enhancing and flux-weakening with no increasing machine bulk, as well as the numbers of stator and rotor slot. The working principle of proposed machine is deeply studied, as well as basic electromagnetic characteristics are calculated by finite element method, including no-load magnetic flux linkage, no-load back electromotive force, cogging torque and output torque. In addition, the processes of flux-enhancing and flux-weakening are analyzed. Finally, one prototype with one kilowatt was built and its static characteristics were tested. The results show that the proposed HEFMM has the features of high torque density, small cogging torque and wide speed range, which is promising candidate for electric vehicle direct drive field. [ABSTRACT FROM AUTHOR]

The development of electric vehicles (EVs) presents the challenge of optimising electric machines to enhance efficiency, compactness, noise, vibration, harshness (NVH), and affordability, while reducing the dependence on heavy rare-earth materials to reduce the CO2 footprint of electric powertrains. This paper introduces a comprehensive optimization approach for the electromagnetic design of permanent magnet synchronous machines (PMSMs), employing a combination of Design of Experiment (DoE) and Robust Neural Networks (RNN). The optimization framework is utilised to comprehensively address the multiple objectives of an electric machine, including efficiency, noise, vibration, harshness (NVH), and cost. The integration of Artificial Intelligence (AI)-driven modelling has resulted in significant performance improvements, achieving up to 96% total efficiency over the entire load cycle with substantial NVH reductions of up to 20 dB, while reducing the magnet rare earth materials by 35% compared to the baseline. Furthermore, this methodology reduces the simulation time by up to 90%, demonstrating the potential of combining neural network optimization with conventional finite element simulation techniques. The validation of the AI-driven optimization approach with the measurement of the baseline and optimised electric machines for efficiency and vibration is demonstrated for correlation. [ABSTRACT FROM AUTHOR]

This paper addresses the determination of the electromagnetic parameters of multiphase yokeless and segmented armature (YASA) electric machines. Initially, we briefly review dynamic models useful for predicting the transient behavior of three-phase and five-phase permanent magnet (PM) synchronous machines. Then, analytical expressions are derived specifically for YASA machines, which allow the determination of the following parameters from the models: (i) phase resistance, (ii) synchronous inductance, and (iii) PM-flux linkage. To validate the parameters, we use numerical results obtained with the finite element method and experimental results concerning a YASA prototype under two different winding connections, with one connection defining three phases ( m = 3 ) and the other five phases ( m = 5 ). The numerical and experimental results show that the expressions proposed here provide a good estimate for the electromagnetic parameters for both phase numbers. Finally, to test and validate the parameters analytically obtained for m = 5 , they are used in a transient dq-model of an existing five-phase YASA machine running under field-oriented control. [ABSTRACT FROM AUTHOR]

Advanced slot and winding designs are imperative to create future high performance electrical machines (EM). As a result, the development of methods to design and improve slot filling factor (SFF) has attracted considerable research. Recent developments in manufacturing processes, such as additive manufacturing and alternative materials, has also highlighted a need for novel high-fidelity design techniques to develop high performance complex geometries and topologies. This study therefore introduces a novel physics-informed machine learning (PIML) design optimization process for improving SFF in traction electrical machines used in electric vehicles. A maximum entropy sampling algorithm (MESA) is used to seed a physics-informed Bayesian optimization (PIBO) algorithm, where the target function and its approximations are produced by Gaussian processes (GP)s. The proposed PIBO-MESA is coupled with a 2D finite element model (FEM) to perform a GP-based surrogate and provide the first demonstration of the optimal combination of complex design variables for an electrical machine. Significant computational gains were achieved using the new PIBO-MESA approach, which is 45% faster than existing stochastic methods, such as the non-dominated sorting genetic algorithm II (NSGA-II). The FEM results confirm that the new design optimization process and keystone shaped wires lead to a higher SFF (i.e. by 20%) and electromagnetic improvements (e.g. maximum torque by 12%) with similar resistivity. The newly developed PIBO-MESA design optimization process therefore presents significant benefits in the design of high-performance electric machines, with reduced development time and costs. [ABSTRACT FROM AUTHOR]

The trend towards electrification in mobility has led to the increased use of silicon carbide (SiC) semiconductors. These semiconductors are more efficient but also present challenges related to electromagnetic interference (EMI) due to their higher voltage derivatives. This paper introduces a new high-frequency impedance model for electrical machines. The proposed model distinguishes itself from existing approaches by being entirely derived from Finite Element Method (FEM) simulations, which include capacitances in the magnetic simulation. This approach achieves a balance between computational efficiency and high accuracy across the entire frequency spectrum, ranging from 100 Hz to 50 MHz. The model provides valuable insights during the design phase and was rigorously validated using data from 28 samples of an industrial machine. [ABSTRACT FROM AUTHOR]

This paper introduces a technique aimed at improving the performance of an interior permanent magnet synchronous machine (IPMSM) by reducing torque ripple and radial force harmonics. Unlike conventional IPMSMs, the proposed method employs a variable airgap length that is defined by a mathematical function. Two distinct rotor shapes are investigated to determine the most efficient design. Finite Element Analysis is employed to assess both the electromagnetic and mechanical attributes of the proposed motors. It compares the results for three operating points of the shaped motor with those of a conventional one. The investigation delves into the influence of rotor geometry on key output parameters, including Back Electromotive Force (back‐EMF) harmonics, average torque, cogging torque, torque ripple, efficiency, power factor, and radial force harmonics. The findings indicate that optimising rotor shape can significantly enhance IPMSM performance by reducing torque ripples and radial force harmonics, while simultaneously increasing average torque and efficiency at different operating points. [ABSTRACT FROM AUTHOR]

In this paper, counter rotating dual rotor wound field flux switching wind power generator is revisited to study the generating characteristics of the AC output power curves based on finite element analysis (FEA) and experimental study. Analysis are performed under dynamic conditions, such as variable resistance, field excitation and speed. Also, electromagnetic performance is studied under variation of the field and armature currents. Analysis reveals that outer port machines with higher power capability and better electromagnetic performance compared to the inner port counterparts, although with higher fluctuations exhibited on the torque profiles of the former due to higher slotting effects. From the power generation characteristics curves, it is clear that the developed wind generator is able to produce reliable performance over a wide operating range. The accuracy of the FEA predicted results are validated, experimentally. The cover image is based on the Research Article Generating characteristics and experimentation of counter rotating dual rotor wound field flux switching wind generator by Wasiq Ullah et al., https://doi.org/10.1049/elp2.12374. [ABSTRACT FROM AUTHOR]

An optimal electric machine design task can be posed as a constrained multi-objective optimization problem. While the objectives require time-consuming finite element analysis, constraints, such as geometric constraints, can often be based on mathematical expressions. This article investigates this mixed computationally expensive optimization problem and proposes a computationally efficient optimization method based on evolutionary algorithms. The proposed method always generates feasible solutions by using a generalizable repair operator and also addresses time-consuming objective functions by incorporating surrogate models for their prediction. The article successfully establishes the superiority of the proposed method over a conventional optimization approach. This study demonstrates how a complex engineering design task can be optimized efficiently for multiple objectives and constraints requiring heterogeneous evaluation times. It also shows how optimal solutions can be analysed to select a single preferred solution and harnessed to reveal vital design features common to optimal solutions as design principles. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional turbulent fluid dynamics numerical model of a 311 MVA full hydroelectric power plant unit is made, using the finite element method, to study and understand the ozone transport mechanisms inside the enclosured electric machine structure. In the real world, ozone is produced by partial discharges related to faults on stator bars. In order to analyse ozone transport from localised sources, a 3D fluid dynamic model of a complete hydrogenerator in operation is developed and presented for the first time. The model has a high level of geometric detail. Furthermore, a new proposal to simplify the modelling of radiators is implemented and validated. The modelled structure is based on a Campos Novos hydrogenerator electric machine and it consists of 378 coil-type stator bars made of copper covered by mica and, more externally, by a semiconductor coating layer. Other parts are also represented, including the stator core and air directors made of stainless steel, copper radiators, the rotor with its epoxy surface, and the concrete floor and concrete external walls. In the fluid dynamics model, a finite element mesh was designed to represent the air regions inside the hydrogenerator and the material surfaces that react with ozone (with their respective reaction rates), where the airflow and ozone transport are modelled using the Navier–Stokes equations and the mass conservation law. Partial discharge sources are represented by ozone sources with prismatic shapes, placed on surfaces of stator bars. Ozone concentrations have been calculated inside and around the generator machine. The rotor radius is 3.8075 m and its rotation frequency is 200 RPM. Radial air velocity due to interpole ventilation is also considered (2.2 m/s, as experimentally verified in loco. The radial velocity in the vicinity of the radiators is 3 m/s. It has been concluded that the ozone transport profile is influenced by the source positioning on the stator bars in such a way that source pinpointing is possible and it depends on determining the local and global maxima areas of ozone concentration at the radiators. [ABSTRACT FROM AUTHOR]

In the past decade, car manufacturers have started electrifying the traction chain of their vehicles. Although these vehicles attract more and more drivers, most of them have a limited range and are prohibitively expensive. Manufacturers must therefore offer high-performance conversion chains (particularly in terms of efficiency) while controlling costs. The power converter is a particularly crucial element of the conversion chains: it supplies the traction motor, and its structure and the way it is controlled can greatly influence the overall efficiency of the drive train. This paper studies two conversion structures that can be used as vehicle power converters, which are modeled and associated with an electric machine. The first is a classical three-phase inverter, and the second is a breakthrough architecture called IBIS (Intelligent Battery Integrated System). This battery integrates the conversion function directly into the battery, which reduces material costs. Two loss phenomena are also studied and modeled (with the help of finite element methods): iron losses in the electrical machine (magnetic losses in the ferromagnetic material used) and copper losses in the conductors (AC and DC losses in the conductors). The impact of the architecture is evaluated on a set of operating points from a road cycle standardized by the WLTP procedure. [ABSTRACT FROM AUTHOR]

The segmental translator linear switched reluctance motor (STLSRM) is a special type of linear switched reluctance motor (LSRM) that has more output power than its conventional type. Therefore, it can be a good choice for certain applications. Heat is one of the factors limiting the output in machines. Therefore, predicting the thermal distribution of machine is as important as the magnetic design. A comprehensive thermal model is presented based on the lumped parameter approach for STLSRM, which predicts temperature distribution in different parts of this motor, including slot winding, end‐winding, stator pole, stator yoke, and the moving part. Considering that the proposed thermal model depends on dimensions and materials used in machine, it can be used for other designs of the STLSRM. The presented thermal model is applied to a typical STLSRM and temperature is determined in its different parts. The simulation results are then compared with the results of 3‐D thermal modelling based on the finite element method (FEM) for validation. [ABSTRACT FROM AUTHOR]

At present, the majority of electric machine design software employs its own unique machine data structure. However, when users need to transfer their designs between software, they are often faced with significant obstacles or cannot obtain a parametric model suitable for optimization. In order to solve this issue, a universal parametric modeling framework is proposed for electric machine design. The geometric structure is strictly constrained to ensure that the model will not interfere with each part because of the randomness of input parameters. A data structure consisting of points, lines, and surfaces is constructed, and a conversion interface for parametric modeling with different software is established. Consequently, this universal framework can automatically generate parametric models appropriate for different finite element analysis (FEA) software according to the input parameters. The framework is especially convenient for users who need to design or optimize an electric machine, particularly when FEA software is required for verification. Numerical verification is performed using different software based on interior permanent magnet (IPM) synchronous machines to demonstrate the effectiveness of the framework. [ABSTRACT FROM AUTHOR]

Pulse–width modulated inverters are commonly used to control electrical drives, generating a common mode voltage and current with high–frequency components that excite the parasitic capacitances within electric machines, such as permanent magnet synchronous machines or induction machines. This results in different types of bearing currents that can shorten the service life of electric machines. One significant type of inverter–induced bearing currents are high–frequency circulating bearing currents. In this context, this work employs finite element analysis and time-domain simulations to determine the common mode current and circulating bearing current for various permanent magnet synchronous machine designs based on the traction machines of commercial electric vehicles with a focus on the stator. The results suggest that the ratio between the circulating bearing current and common mode current is much smaller in permanent magnet synchronous machines for traction applications than previously established in conventional induction machines, with values below 10% for all analyzed designs. A further increase in the robustness of such electric machines to the detrimental effects caused by the inverter supply could be achieved by reducing the parasitic winding–to–stator capacitance or by increasing the stator endwinding leakage inductance. [ABSTRACT FROM AUTHOR]

The magnetic pressure generated in the stator of electric machines can be a significant source of noise and vibration. The vibration behavior of the stator and such mechanical structures primarily depends on their geometry. Although the stator is often considered a simple structure, its teeth are not included in this assumption. In this paper, we endeavor to evaluate the impact of stator geometrical variability on the vibration behavior of electric machines. Our sensitivity study reveals that natural frequencies and frequency response functions are highly sensitive to geometrical variability. To account for this, we conducted a variability propagation study using a stochastic finite element model. Our findings show negligible variability on the natural frequencies but a high variability on the frequency response functions, even with low input variability. As anticipated, our study highlights the critical role of accounting for geometrical variability to enhance the accuracy of finite element models and strengthen their predictive power. However, the main contribution of this work is that the vibration behavior of the stator is not coupled, implying that the impact on natural frequencies does not necessarily reflect the same effect on the frequency response function. [ABSTRACT FROM AUTHOR]

In this paper, an oil-cooling induction switched reluctance machine (ISRM) is offered. The stator and rotor of the electric machine are non-segmental. However, by placing coils on the rotor, a short magnetic flux path is achieved in the rotor and stator cores. As a result, a higher torque with lower losses is generated. This configuration can be used in high-power electric motors for electric and hybrid vehicles. ISRM is a novel machine and there is a lack of access to its operation and data characteristics. ISRM can be designed in different configurations with various stator and rotor pole numbers and winding strategies. In this study, an oil-cooling three-phase ISRM with 6 stator poles and 4 rotor poles was considered. Firstly, a 2D finite element model of it is created, and its magnetic properties extracted, the flux path, torque and efficiency of the ISRM are calculated, and the results are presented. Secondly, the thermal performance of the motor is analyzed using ANSYS Motor-Cad software. Finally, a prototype of the ISRM and its appropriate drive with the oil cooling system is built and tested. The experimental results and conclusions which prove the ability of the presented machine are presented in the last parts of the paper. [ABSTRACT FROM AUTHOR]

Electric machines built according to the modular principle – with several three-phase windings on a stator – are a new direction of modern electromechanics, because they have a number of advantages compared to traditional singlewinding machines. Among these benefits, the most important are increased efficiency and fault tolerance, which is especially important for self-powered electric vehicles. However, the presence of a mutual magnetic coupling between the modules, as well as their unequal electrical load, amplify the electromagnetic torque ripple inherent in one or another electric drive system. In this work, the electromagnetic torque ripples in a dual three-phase (DTP) brushless DC motor (BLDCM) under different loads of its modules were investigated for the cases of absence and presence of mutual magnetic coupling between armature winding sets and in the cases of the drive operation in open and closed control systems. The research was carried out by means of simulation in the Matlab/Simulink environment on a circular model of real mock-up sample of DTP permanent magnet machine developed based on the results of its magnetic field simulation using the finite element method. Adequacy of simulation results is confirmed by experimental investigation. The results of the DTP BLDCM simulation studies showed an increase in the relative electromagnetic torque ripples of individual modules due to both the presence of magnetic coupling between winding sets and the deviation from their equal loading. However, at the level of the whole DTP BLDCM, a significant mutual compensation the electromagnetic torque ripples of the modules is shown, especially if they are magnetically coupled. The presence of closed-loop control systems of individual modules significantly reduces the electromagnetic torque ripples caused by different loading of the modules, especially in the case of magnetically uncoupled modules. References 26, figures 7, tables 3. [ABSTRACT FROM AUTHOR]

This study elaborates upon a new modular split‐tooth permanent magnet‐assisted switched reluctance motor (MSTPM‐SRM). In the proposed topology, the stator comprises six modular E‐cores in which the middle poles are split into two teeth. Two permanent magnets (PMs) are placed between each module's middle and side poles. Primarily, the proposed topology is introduced. Next, the principle of operation of the proposed topology are elucidated, and the magnetic equivalent circuit analysis is adopted in order to validate the operational basics. It is proved that the embedded PMs significantly increase the air‐gap's flux density and adjusts the poles' flux density. The flux density distributions, static, and steady‐state characteristics of the proposed MSTPM‐SRM motor and its PMless counterpart are extracted by utilising 2‐D finite element analysis. It is illustrated that the average torque of the proposed MSTPM‐SRM is dramatically increased compared to its PMless counterpart, especially at high excitation currents. Furthermore, the cogging torque analysis is done and it is shown that the proposed structure has approximately zero cogging torque. Finally, a prototyping version of the proposed motor is fabricated, and the experimental results are elicited. It is shown that the experimental results endorse the simulation results. [ABSTRACT FROM AUTHOR]

This paper investigates the torque generating capabilities and performance comparison of induction machines (IM) and interior-permanent magnet (IPM) machines for electric vehicle (EV) traction applications. Electromagnetic performance characteristics, such as torque, torque ripple, air-gap flux density, etc. are quantitatively compared by changing the level of electric loading. Other performance metrics such as saturation factor, power losses, efficiency, and so on, as well as the flux-weakening capability and efficiency map have also been compared. For calculations of the electromagnetic performance characteristics, 2D time-stepping finite element analysis (FEA) has been employed. It has been revealed that due to the reduction in torque components of IPM machine as a consequence of magnet demagnetization, it cannot generate toque as high as IM under overloading operating conditions. A thorough review of the literature on comparative studies on the electrical machines used in EV or Hybrid EV (HEV) applications is also included. [ABSTRACT FROM AUTHOR]

In recent years, WEDM has been adopted in precision machining as an important alternative machining method because of its greater flexibility and lower wear cost compared with traditional machining, whereas wire breakage during WEDM is an unignorable problem that influences the machining quality and efficiency. Therefore, it has been a research topic of considerable interest. This work focuses on exploring the reason for the wire breakage. Firstly, by observing the wire after discharges and using the finite element method, a complete thermal model considering both latent heat and flushing efficiency was built. With this model, the simulation of the crater on the wire was finished. Then based on the result gotten from the simulation and experiment, the heat partition ratio to the wire was found as 46.74% by inverse fitting. After that, a wire breakage experiment was done and through locating the position of 50 discharges before wire breakage it is found that 34% of discharges were located within a range of 2 mm, and the minimum area in the wire cross-section only remained 41.88% compared with the original wire. This kind of decrease in the cross-section area made the stress higher than the UTS of the wire and caused the wire breakage. The findings of this work allow for a more in-depth understanding of the effect of discharge accumulation on wire breakage. [ABSTRACT FROM AUTHOR]

Featured Application: The presented results can be used in designing synchronous homopolar machines and railway undercar generators. The article presents the optimal design of a 35 kW brushless synchronous homopolar generator without permanent magnets for railway passenger cars. The excitation winding of the generator is located on the stator, and the toothed rotor has no windings. The generator characteristics are optimized considering the required constant power speed range. A single-objective Nelder–Mead algorithm and 2D Finite Element Analysis were used for the optimization. As a result of the optimization, power losses are significantly reduced over the entire operating range of the generator rotational speed, the current capacity of the solid-state rectifier, and the torque ripple. A comparison of the calculated characteristics of the generator under consideration with the characteristics of a commercially available undercar generator shows that the active volume is reduced by a factor of 2.1, and the losses are significantly reduced over the entire operating speed range. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multi-phase single-turn permanent magnet synchronous motor (MSPMSM) to meet the stringent requirements of electric aircraft, such as high power density, high torque, and low mass and volume. The MSPMSM features a unique single-turn winding configuration, which can reduce the coil overhang, increase the power density and torque, and reduce the weight of the motor in conventional multi-turn motors. The proposed MSPMSM is studied by the finite element method (FEM) and compared to a conventional PMSM with the same geometry and PM usage. The performance comparison results under different load conditions show that the proposed MSPMSM has higher torque and power density than the conventional motor. [ABSTRACT FROM AUTHOR]

Thermal stresses on the induction machine are the main cause of reliability reduction, which can lead to further faults in the machine. Using the thermal sensors to determine the temperature of the electric machine is costly and difficult; therefore, indirect methods have been considered to this end. One of these methods is utilizing the thermal model of the induction machine, which can determine the temperature of various parts of the motor without requiring any additional circuits for signal injection or the use of rotor resistance estimation techniques. This paper presents a modified thermal model of the induction machine. In this model, each rotor bar's current is designated as a heat source. Therefore, to solve the new model, it is required to calculate the rotor bars' current. The currents of the rotor bars of a squirrel cage induction motor are calculated by using the motor terminals data measured with an experimental test setup and both winding function and finite element methods. Then, the losses of the rotor cage are obtained by these currents. By inserting these losses into the modified lumped parameter thermal model of the machine, the rotor temperature will be determined. The results have been validated by analyzing the motor temperature with MotorCAD software, and it has been observed that the new proposed model achieves more accuracy compared to the conventional model. In addition, the accuracy of MotorCAD simulation was confirmed by implementing a temperature sensor in stator winding and comparing the achieved temperature with MotorCAD simulation results. [ABSTRACT FROM AUTHOR]

In order to obtain cold extruded internal thread with better quality, the cold extrusion and cutting of 42CrMo4 ultra-high strength steel internal thread are carried out. The tooth shape, microstructure and residual stresses at different orientations are established and discussed. The elastic-plastic finite element model is then established to simulate the cold extrusion processing of internal thread. It is used to analyze the effects of key processing and design parameters (including workpiece bottom hole diameter, machine tool speed, lubricating medium and margin ratio) on tooth shape and the residual stresses around the thread surface. The results show that each parameter has a certain influence on the residual stress of the thread after extrusion processing. The diameter of the bottom hole directly determines the magnitude of the residual stress, and the change of the lubricating medium has no obvious effect on the residual stress. In general, the residual stress along the depth direction of the thread appears as compressive stress on the surface, and shows a trend of increasing first and then decreasing, after reaching the critical point, it quickly changes into tensile stress, finally tends to be flat. The technological parameters of cold extrusion of internal thread are optimized by orthogonal design. After optimization, the maximum residual compressive stress increases by 17.52% and the maximum residual tensile stress decreases by 19.13%. Although the thread height is reduced by 0.05 mm, the surface quality may be improved and the connection strength of the thread still meets the requirements. [Display omitted] • The cold extrusion and cutting of 42CrMo4 ultra-high strength steel internal thread are carried out. • Cold extrusion is beneficial to generate residual compressive stress field near the hole wall, which may eliminate the influence of stress concentration and reduce the sensitivity of fatigue cracks, and finally restrain the rate of crack initiation and propagation. • The effects of key processing and design parameters on tooth shape and the residual stresses around the thread surface are discussed. • After optimization, the maximum residual compressive stress increases by 17.52% and the maximum residual tensile stress decreases by 19.13%. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous generators (PMSGs) with high output density per unit volume are becoming widespread in wind-power generation systems. Among them, spoke-type PMSGs are more challenging to magnetize than other PMSGs, owing to their structural characteristics. Magnetization performance is critical because it is directly related to the demagnetization and mass productivity of permanent magnets, and load performance is reduced when non-magnetization occurs due to the low magnetization performance. Additionally, the starting performance is crucial in wind turbines and is influenced by the cogging torque of the PMSG. This is because starting a wind turbine with a large cogging torque is more challenging. Therefore, this study proposes a spoke-type PMSG rotor shape design for low capacity wind turbines that considers magnetization and cogging torques. We analyzed the principle of magnetization and the factors influencing magnetization performance, and designed a rotor shape with improved magnetization performance. Additionally, we applied an asymmetric rotor barrier structure to reduce the cogging torque and analyze the performance of the final model using finite element analysis. We analyzed the temperature saturation during the operation of the final model using a thermal network method and validated the irreversible demagnetization accordingly. [ABSTRACT FROM AUTHOR]

Because of exclusive characteristics of Switched Reluctance Motor (SRM) particularly simple and robust structure and high reliability, it can be a good choice for many industrial applications. In terms of structure and performance principles, the Linear Switched Reluctance Motor (LSRM) is similar to rotary SRM (RSRM) and therefore their advantages are identical. The Segmental Translator Linear Switched Reluctance Motor (STLSRM) is a special type of LSRMs that can produce a higher thrust density in comparison to the simple type of LSRM. One of the most important models for predicting the characteristics of electric machines is the model based on the Magnetic Equivalent Circuit (MEC), which can be used to predict the performance characteristics of machines. Although the STLSRM has significant advantages, no MEC model has been introduced for it so far. With the aim of predicting the static and dynamic characteristics of this motor, a new analytical model based on MEC method is developed in the present paper. In addition to simplicity, the developed model has acceptable accuracy and speed. The proposed model is utilized for a three-phase STLSRM and different static and dynamic characteristics of the motor including static flux-linkage, static force, instantaneous current waveform and instantaneous thrust waveform are predicted. To validate these obtained simulation results, they are compared with those derived from the Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

• Cogging torque is one of the problems for permanent magnet machines. • Magnetic permeance distribution is one of the components of the cogging torque. • Unequal rotor slot arc (URSA) angles help to manipulate the magnetic permeance distribution. • URSA method has promising outcomes to mitigate the cogging torque. Cogging torque is a crucial and offending problem for electric machines that consist permanent magnets. Flux switching permanent magnet (FSPM) machines have magnets embedded inside the stator coils. Due to the interaction between the stator magnetic flux and the rotor steel, cogging torque occurs. To express this interaction, Magnetic Permeance Distribution Model is implemented in this study. To minimize the cogging torque, unequal rotor slot arc (URSA) technique is developed and cogging torque is calculated by using finite element method. An optimization study is performed to get the minimum value of the cogging torque under reasonable output torque. Results prove that, the proposed URSA method have promising outcomes for cogging torque reduction. [ABSTRACT FROM AUTHOR]

In recent years, the mobility sector is undergoing a revolution, which is resulting also into a worldwide spread of light electric vehicles, such as electric scooters and bicycles. The increasing public concern about environmental problems further feeds this revolution. Electric-bicycles (or e-bikes) are a new trend which fits different riders' needs. In fact, they offer extended range and ease of use, allowing riders to travel in urban centres, but also to take longer trips. E–bikes are reliable, easy to ride, affordable, and they help people live and travel a little greener, with a great benefit for their health. Many Companies (such as Brose, Bafang, Bosch and Shimano) developed performing e-bike motor drives. However, there is not a detailed general procedure to help the choice and design of electric bikes, in particular concerning the electric machine. This review focuses on the analysis of different motors for e-bike application. First, the e-bike system state of art is presented. The pedal-assist and power-on-demand e-bike system typologies are presented, together with the most popular parallel configuration and the less common series configuration. Further on, the environmental resistances are analysed for a traditional bicycle system and then the force balance is extended to the electric vehicle example. The most common Lithium-ion battery and the battery management system state of art is discussed, presenting design schemes and typical performances. Concerning the electrical machine, some electromagnetic design approaches are described, together with some data on commercial motors. Finite element analysis of a common motor model is carried out and some experimental tests are presented to highlight their capabilities. Different control strategies are compared, including innovative solutions and new trends. [ABSTRACT FROM AUTHOR]

Interior permanent-magnet synchronous machines are widely spreading in automotive and vehicle traction applications, because of their high efficiency over a wide speed range. This capability can be achieved by appropriated control strategies: Maximum Torque per Ampere (MTPA), Flux Weakening (FW) and Maximum Torque per Volt (MTPV). However, these control trajectories are often based on an simplified magnetic model of the electrical machine. In order to improve the evaluation of machine output capabilities, nonlinear magnetic behavior must be modeled. This is not only related to the final application with a given drive and control structure, but also during the design process of the electric machine. In the design process, the output torque Vs. speed characteristic must be calculated following MTPA, MTPV and FW in the most accurate way to avoid significant error. This paper proposes a set of algorithms to compute MTPA, FW and MTPV curves for interior permanent-magnet synchronous machines taking into account the machines' nonlinearities caused by iron saturation and compares differed approaches to highlight the torque–speed capabilities for the same machine following different methods. The algorithms are based on the maps of the equivalent inductances of a reference interior permanent-magnet synchronous machine and inductances maps were obtained via 2-D Finite Element Analysis over the machine's operating points in i d − i q reference plane. The effects of different 2-D finite element methods are also computed by both standard nonlinear magnetostatic simulations and Frozen Permeability simulations. Results show that the nonlinear model computed via frozen permeability is more accurate than the conventional linear and nonlinear models computed via standard magnetostatic simulations; for this reason, during the electrical machine design, it is important to check the expected performance employing a complete inductance map and frozen permeability. [ABSTRACT FROM AUTHOR]

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Electrical machine design optimization is an expensive procedure as it contains numerous variables and multiple objectives. Therefore, it might require hundreds of time‐consuming finite element analyses (FEA). Surrogate models are one of the superior alternatives that can overcome the computational burden of FEA. However, in optimization problems with sensitive input‐output relationships, surrogate models can lack accuracy or suffer from unreasonable initial FE‐computational cost. To tackle this problem, this work presents a novel strategy called Waveform‐Targeted Surrogate Modeling (WTSM) that improves the computational efficiency of surrogate‐based design optimization of electrical machines by modifying the model construction process. In this paper, an Interior Permanent Magnet Machine (IPMSM) is studied to evaluate the proposed strategy's performance compared to the conventional Black Box Modeling (BBM) method. A two‐step assessment procedure consisting of multiple scenarios has been developed to analyse the reliability of the WTSM concerning different training‐validation datasets. Meanwhile, the Kriging model and Latin‐Hypercube‐Sampling (LHS) method are employed for surrogate model construction purposes. From the discussion and the results, it can be found that the proposed WTSM strategy can significantly increase the accuracy of the surrogate modelling procedure while the required computational cost can be reduced. [ABSTRACT FROM AUTHOR]

Accurate modeling of slotting and magnetic saturation effects has been two main challenges for analytical modeling of electric machines. In this article, first, different techniques such as sub‐domain (S‐D) model, winding function theory, magnetic equivalent circuit (MEC) model, and conformal mapping (CM) method are introduced to analytical model and analysis of electric machines. These techniques are also compared in terms of their accuracy, and computational complexity. Second, with respect to the comparison results, a new hybrid analytical model is presented for electromagnetic modeling of wound rotor induction motors, which consider the modeling accuracy of slotting and magnetic saturation effect, simultaneously. In this way, the air‐gap region is modeled by using S‐D model, and the iron parts are considered by using MEC model assisted by CMs. In final, the analytical results are verified by comparing with corresponding results obtained through finite element method and experiment set‐up. [ABSTRACT FROM AUTHOR]

Slotting effect in electric machines reduces flux per pole that effect magnetic flux density distribution in the air gap which induces harmonics in magnetic flux density causing flux pulsation, that in turn generates dominant torque pulsation in the form of cogging torque and torque ripples. To overcome the abovesaid demerits, a novel outer rotor field-excited flux-switching machine (OR-FSFSM) with a combined semi-closed and open slots stator is proposed in this study. The developed OR-FEFSM offers a high-power factor, due to the utilization of the semi-closed slot for armature coils. The open slot stator structure was chosen for the field excitation coil, which effectively suppresses leakage reluctance that causes flux pulsation. Thus, the influence of torque ripples is reduced, and the average torque is improved. In order to investigate the effectiveness of the proposed OR-FEFSM, a detailed study of stator slot and rotor pole combinations are performed. Based on simplified mathematical formulation, 12S/7P (stator slot/rotor poles), 12S/11P, 12S/13P, and 12S/17P are the most feasible combinations. Finite Element Analysis (FEA) based on comprehensive electromagnetic performance is performed on each combination, and found that 12S/13P offers the highest average torque of 4.62 Nm, whereas 3.72 Nm, 2.72Nm, and 1.68 Nm average torque is offered by 12S/17P, 12S/7P, and 12S/11P, respectively. Based on the initial analysis, 12S/13P was considered for further analysis and optimized using JMAG built-in Genetic Algorithm (GA). Moreover, thermal analysis was performed, and the proposed design was compared with the conventional design. [ABSTRACT FROM AUTHOR]

Machining deformation compensation technology based on on-machine measurement has been widely used in the field of thin-walled part machining. However, few research has been conducted on sampling methods for the measurement of thin-walled parts. In this study, we considered the influence of machining deformation in thin-walled regions, established a machining deformation prediction model (MDPM) based on the finite element method (FEM), and applied it to the sampling optimization process. Furthermore, we proposed an adaptive sampling method based on the maximum corresponding point deviation (MCPD) at the measurement point interval of the non-uniform rational B-spline (NURBS) curve. The proposed method was compared with three commonly used sampling methods (uniform sampling, curvature-based sampling, and maximum deviation-based sampling). Sampling experiments were performed with one NURBS curve and two machined thin-walled parts. The experimental results show that the proposed method is superior to the three commonly used sampling strategies in terms of reconstruction accuracy, sampling efficiency, and result stability. [ABSTRACT FROM AUTHOR]

This paper investigates a novel integrated AC–DC hybrid magnetic bearing (HMB) to reduce the volume, weight, manufacturing, and operation cost of magnetic suspension motors. Two radial MBs and an axial MB are integrated with the proposed HMB. The five-degree-of-freedom (5-DOF) suspension is realized in one unit. Two axially polarized permanent magnets provide the radial and axial bias fluxes. First, the HMB structure and the suspension mechanism are introduced. Second, based on the method of equivalent magnetic circuits, magnetic circuits are calculated. The mathematical models of suspension force are discussed. Third, the main parameters of the 5-DOF AC–DC HMB are given. The 3D finite element method (FEM) is adopted to analyze the proposed system's electromagnetic characteristics, and the suspension mechanism of the 5-DOF is verified. The radial suspension forces versus the radial control current, the axial suspension forces versus the axial control current, the relationship between the axial suspension force and the axial control current with the X direction offset, and the relationship between the radial suspension force in the X direction and the axial control current with the Z direction offset are calculated. Based on the research results, it is shown that the HMB structure is compact and reasonable, and the mathematical models and suspension mechanism are correct. [ABSTRACT FROM AUTHOR]

In this present work, finite element analysis (FEA)-based simulation of end-milling of AISI1045 steel using tungsten carbide tool was performed using DEFORM-3D simulation software. Usui tool wear model, Johnson-cook material model and adaptive remeshing are considered during machining simulation. The impact of machining variables rate of feed, tool speed, and depth of cut was investigated, and the best integration of variables was distinguished for lower cutting temperature, principal stress, cutting forces, effective stresses, tool wear, and effective strain. The obtained results were correlated using experimentation in a vertical machining center attached with a Kistler tool dynamometer with data acquisition setup for capturing the cutting forces, and an infrared (IR) thermometer was used to measure the cutting temperature, and a comparison was done. Results showed a good correlation. There is a relationship between experimental and numerical results, and simulation findings can be utilised for interpreting the influence of machining parameters. [ABSTRACT FROM AUTHOR]