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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 framework to 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 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]

Introduction. Recently, the theory of a special class of cascade slow-speed non-contact induction-synchronous electrical machines (ISEM) has been developed. This allowed to obtain a combination of positive properties from conventional induction and synchronous electric machines. Problem. The lack of circuit and field models of ISEM imposes restrictions on further research of electromagnetic, mechanical and energy processes, in transient and quasi-steady modes of its operation. Goal. Development of 3D and adapted 2D circuit-field models of ISEM, decomposition methods, and dynamic synthesis with adaptation of electromagnetic parameter coupling conditions at the boundaries of calculated subdomains of ISEM. Methodology. Spatial elements of ISEM design are represented by separate spatial calculation subareas. The conditions of compliance with electromagnetic processes, which are formed by a complete calculation area and separate spatial calculation subareas of ISEM, are accepted. The influence of end effects and the parameters of the frontal parts of ISEM windings are determined by the inequality of the magnetic field energy of separate calculation subareas. These parameters, including end effects, are displayed as circuit elements in the 2D circuit-field model. Results. The obtained combination of 3D area decomposition methods and dynamic synthesis with adaptation of electromagnetic parameters coupling conditions at the boundaries of its calculated ISEM’s subdomains. The proposed technique for determining the resistance and inductive resistances of the frontal parts of the ISEM windings, taking into account edge effects. The accuracy and effectiveness of the proposed methods is confirmed by the results of an experimental study. Originality. An adapted dynamic 2D circuit-field model of transient processes of ISEM has been developed, which allows taking into account parameters of the frontal parts of its windings. Practical value. The proposed methods can be used for various types of electrical machines. References 27, tables 3, figures 12.

The design of electric machines for the aviation industry is associated with a large number of difficulties, one of which is the selection of the optimal number of slots that ensures optimal performance of electric machines. This is especially important for multi-pole designs, where an incorrect number of poles can result in unsatisfactory performance both in terms of electromagnetic parameters and mechanical parameters. The article describes the slots number selection process for a low-speed motor to drive the aircraft propeller with a power of 250 kW at a speed of 2000 rpm. The process of choosing the number of slots is based on the consideration of each option according to 12 criteria, each of which is described in detail in this paper. [ABSTRACT FROM AUTHOR]

Introduction. Recently, the theory of a special class of cascade slow-speed non-contact induction-synchronous electrical machines (ISEM) has been developed. This allowed to obtain a combination of positive properties from conventional induction and synchronous electric machines. Problem. The lack of circuit and field models of ISEM imposes restrictions on further research of electromagnetic, mechanical and energy processes, in transient and quasi-steady modes of its operation. Goal. Development of 3D and adapted 2D circuit-field models of ISEM, decomposition methods, and dynamic synthesis with adaptation of electromagnetic parameter coupling conditions at the boundaries of calculated subdomains of ISEM. Methodology. Spatial elements of ISEM design are represented by separate spatial calculation subareas. The conditions of compliance with electromagnetic processes, which are formed by a complete calculation area and separate spatial calculation subareas of ISEM, are accepted. The influence of end effects and the parameters of the frontal parts of ISEM windings are determined by the inequality of the magnetic field energy of separate calculation subareas. These parameters, including end effects, are displayed as circuit elements in the 2D circuit-field model. Results. The obtained combination of 3D area decomposition methods and dynamic synthesis with adaptation of electromagnetic parameters coupling conditions at the boundaries of its calculated ISEM’s subdomains. The proposed technique for determining the resistance and inductive resistances of the frontal parts of the ISEM windings, taking into account edge effects. The accuracy and effectiveness of the proposed methods is confirmed by the results of an experimental study. Originality. An adapted dynamic 2D circuit-field model of transient processes of ISEM has been developed, which allows taking into account parameters of the frontal parts of its windings. Practical value. The proposed methods can be used for various types of electrical machines. References 27, tables 3, figures 12. [ABSTRACT FROM AUTHOR]

Due to new requirements regarding the efficiency of electrical machines it is necessary to steadily improve machine concepts or create new ones. Therefore, manufacturing technology has to be continuously improved, adapted or developed new. Forming technology offers an excellent opportunity to implement components for highly efficient electrical machines through its advantages regarding high productivity and high degree of material usage. This paper presents a new method for bending complete stacks of grain oriented electric sheets for use as radially laminated modules in an innovative machine concept with flux barriers. First, the principle of electric drives with flux barriers and the arrangement of the new radial lamination are explained. Then, practical preliminary studies concerning the bending of single sheets are performed. Based on this, the process and tooling for bending of pre-stacked sheets is developed and analysed. Accordingly, an increase in material utilisation of about 30% can be expected compared to classically designed stators. Furthermore, the use of the radially laminated stator principle increases the slot area by about 20% which makes it possible to insert more copper into the slot and thus increase the efficiency of the machine during operation. After validation of the process chain with a demonstrator motor and description of several manufacturing and quality improvements, finally, an outlook is given, and possible further research approaches are discussed. [ABSTRACT FROM AUTHOR]

Equations of mathematical physics, which are solutions of the Laplace's partial differential equation using the method of separation of variables for hollow cylinders of finite length, are considered as the basis of an analytical model for electric machines. The yoke and tooth layer of the stator core are represented in the model by two nested cylinders, and the end zone of the core is represented by several cylinders connected to each other and to the inner nested cylinder. The unknown constants of the separation of variables method are determined from the boundary conditions of the electromagnetic field: scalar magnetic potentials and coordinate components of the magnetic induction do not experience a jump (discontinuity). The magnetic field caused by the magnetomotive force (MMF) of the stator winding is analyzed in the core itself and outside of it: in the end-winding zone. It is shown that the well-known formula for the MMF of the winding in the active part of the air gap can be used to determine the MMF of the end conductors. The flux linkage of the end parts of the coil is calculated, and the inductance of the end-winding leakage of the entire winding is determined based on this. The validity of the initial analytical approaches for solving the mentioned problem is dictated by the use of three-dimensional equations of mathematical physics in a cylindrical coordinate system for electric machines, the majority of which have a cylindrical construction in the active zone. The obtained numerical value of this parameter for a 150-kW valve motor is sufficiently close to the calculated value found using a known semi-empirical formula applied in the practice of electric machine design. [ABSTRACT FROM AUTHOR]

Abstract 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.

The growth of electrical machine applications in high-torque environments such as marine propulsion and wind energy is encouraging the development of higher-power-density machines at ever higher efficiencies and under competitive pressure to meet higher demands. In this study, numerical simulations are performed to investigate the characteristics of air cooling applied to a 3 MW high-torque internal permanent magnet electric machine with integrated power electronics. The whole system of the main machine and two converters at either end are modelled with all details. Effects of different parameters on the total pressure drop and air flow rate to the machine and converters are examined. Results show that by changing the converter outlet hole size, the air flow rate to the machine and converter can be adjusted. Air guides and pin vents reveal excellent performance in the distribution of air to laminations and windings with a penalty of some increase in pressure drop, which is more pronounced when using smaller outlet holes. Furthermore, the air return manifold increases the pressure drop and causes a reduction in air flow rate to the converter. Insulation between compression plate and laminations is an unavoidable component used in electric machines and acts as a thermal insulator. However, it can also significantly augment pressure drop, especially in combination with smaller outlet holes. Thermal studies of the integrated power electronics illustrate that components' temperatures are less than the temperature limit, confirming enough air through the converter. Analysis of power electronics in the case of fan failure provides the operational time window for the operators to respond. [ABSTRACT FROM AUTHOR]

This paper provides a proof of concept for a linear electric generator that can be used to harvest energy from various sources of linear motion, such as vibrations, free-piston engines and wave energy. The generator can be used to power small electronic devices, such as sensors, or charge household batteries. The literature was reviewed to develop an understanding about the applications, control methods, excitation methods and mechanics of rotating and linear electric machines. A bidirectional, two-sided linear machine was designed with two stator cores and a single mover core. The stator windings and mover winding can be independently excited, allowing for three modes: no mover excitation, a DC excited mover, and an AC excited mover. Simulation results showed that the magnetic flux generated by DC excited stator cores were concentrated in the centre of the mover core. The use of two stator cores eliminates lateral flux in the mover core when it is not excited, minimising attraction and repulsion forces. Parametric analysis showed that flux cutting occurred in all operation modes, verifying that the generator will produce power when operating. Hardware tests produced an output current when the machine was electrically and mechanically excited, verifying the proposed design. [ABSTRACT FROM AUTHOR]

Abstract 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.

Homopolar AC Machines (HAMs) are of interest because of low rotor loss and the ability to operate at high speeds. These machines are frequently utilized in flywheel energy storage systems but are dominated by permanent magnet or induction machines in other contexts such as vehicle traction. The aim of this work is to explore a new type of homopolar machine. The Dual Rotor Homopolar AC Machine (DHAM) is proposed herein. The fundamental operating principles of the DHAM are explained, and its torque production and terminal characteristics are outlined. The permanent magnet version of the machine is shown to achieve an extended constant power speed range without impacting the PM field intensity, allowing the use of magnet materials with modest values of intrinsic coercive force. The machine includes a modular sectionalized stator, which is easy to wind and cool. The DHAM relies on sinusoidal airgap reluctances, and so the necessary rotor geometry is derived. A prototype machine is used to validate the operating principle.

With an increasing emphasis on energy efficiency and the widespread adoption of Wide-Band-Gap (WBG) devices, understanding and mitigating EMI is crucial for the reliability and performance of electric drives. This research focuses on high-frequency phenomena induced in electrical machines and the integration of Finite Element Method (FEM) simulations into the drive design process. A novel approach is introduced where a full drive model is experimentally validated using motor impedance obtained from FEM simulations, which is then fitted to a lumped-parameter model with a basic genetic algorithm. The model is validated across the full Electromagnetic Compatibility (EMC) range for conducted emissions, from 10 kHz to 30 MHz. The paper emphasises the importance of an EMI-focused design approach early in the development process to minimise costs, improve reliability, and ensure compliance with EMC standards.

This paper presents a promising winding technique which enables higher power-densities in partially superconducting electrical machines with a slotless stator, e.g., self-supporting windings. Firstly, the formulation for defining the skewing factor of the helical winding is given. Afterwards, the skew angle and how diverse winding configurations can be characterised as a function of this angle is explained, along with different parameters such as the skewing factor, the harmonic content of the magnetomotive force wave in the airgap or the resistance per phase of the winding. The sine-shaped winding, a particular case of helical winding, is shown, with which, thanks to the benefits of the additive manufacturing, a better electromagnetic performance is achieved. Finally, the implementation of the helical winding configuration in a slotless partially superconducting 2 MW high-power and high-voltage electric machine for electric aircraft propulsion is assessed, comparing the machine active part weight and their power density.

Industry is increasingly adopting high-speed electric machines due to their high-power density and low cost. However, increasing the speed leads to many challenges that are worth to study since they have relevant impact on the design of the machine. One of these challenges is the losses in stator winding assembly. At low frequency, losses in windings are usually assumed equal to DC losses. However, at high frequency some phenomena become noticeable and worth evaluating since they lead to noticeable losses. AC losses in windings are due to skin effect, proximity effect, and circulating currents. The main models of AC losses in windings in the literature are presented for both circular and rectangular wires. These models are compared using both interior and surface-mounted permanent magnet synchronous machines. Results show that for proximity effect, analytical model is convenient when considering armature reaction only, however, when considering on load case, hybrid model with simple FEA is suitable thanks to its interesting trade-off between accuracy and computation time, which makes it suitable for large-scale optimization. For circulating currents effect, finite element model is unavoidable. Moreover, two important properties concerning circulating currents are stated as well as their mathematical proofs.

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]

Electric motor development is a challenging task, as higher efficiency requirements and various interdependencies between different engineering domains must be considered. Established design approaches often lack the ability to address these interdependencies because they focus on specific domains and properties. Automated, multidisciplinary design approaches hold untapped potential for optimizing motors in terms of diverse requirements and advancing the development of more efficient and reliable motors. This paper presents a systematic literature review of the current state of research in the multidisciplinary design automation of electric motors. The literature basis comprises 1005 publications that are identified by a systematic internet search. The review of the existing approaches is based on twelve criteria that characterize the design automation task in general, such as knowledge representation or reasoning methods used, as well as criteria specific to electric motor design, such as domains considered and their coupling. The analysis reveals what current approaches are lacking: Consequent analysis and integration of domains, applicability of suggested methods, incorporation of established multidisciplinary design optimization (MDO) architectures, alongside the consideration of passive components in the motor. Aside from the introduction of twelve criteria for systematic charaterization of multidisciplinary design automation of electric motors, this article expands the state of the art by proposing an initial framework to establish process chains tackling the identified gaps in the review. [ABSTRACT FROM AUTHOR]

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The growth of electrical machine applications in high-torque environments such as marine propulsion and wind energy is encouraging the development of higher-power-density machines at ever higher efficiencies and under competitive pressure to meet higher demands. In this study, numerical simulations are performed to investigate the characteristics of air cooling applied to a 3 MW high-torque internal permanent magnet electric machine with integrated power electronics. The whole system of the main machine and two converters at either end are modelled with all details. Effects of different parameters on the total pressure drop and air flow rate to the machine and converters are examined. Results show that by changing the converter outlet hole size, the air flow rate to the machine and converter can be adjusted. Air guides and pin vents reveal excellent performance in the distribution of air to laminations and windings with a penalty of some increase in pressure drop, which is more pronounced when using smaller outlet holes. Furthermore, the air return manifold increases the pressure drop and causes a reduction in air flow rate to the converter. Insulation between compression plate and laminations is an unavoidable component used in electric machines and acts as a thermal insulator. However, it can also significantly augment pressure drop, especially in combination with smaller outlet holes. Thermal studies of the integrated power electronics illustrate that components’ temperatures are less than the temperature limit, confirming enough air through the converter. Analysis of power electronics in the case of fan failure provides the operational time window for the operators to respond.

This paper provides a proof of concept for a linear electric generator that can be used to harvest energy from various sources of linear motion, such as vibrations, free-piston engines and wave energy. The generator can be used to power small electronic devices, such as sensors, or charge household batteries. The literature was reviewed to develop an understanding about the applications, control methods, excitation methods and mechanics of rotating and linear electric machines. A bidirectional, two-sided linear machine was designed with two stator cores and a single mover core. The stator windings and mover winding can be independently excited, allowing for three modes: no mover excitation, a DC excited mover, and an AC excited mover. Simulation results showed that the magnetic flux generated by DC excited stator cores were concentrated in the centre of the mover core. The use of two stator cores eliminates lateral flux in the mover core when it is not excited, minimising attraction and repulsion forces. Parametric analysis showed that flux cutting occurred in all operation modes, verifying that the generator will produce power when operating. Hardware tests produced an output current when the machine was electrically and mechanically excited, verifying the proposed design.

Accurate estimation of the internal temperatures of electric machines is critical to increasing their power density and reliability since key temperatures, such as magnet temperature, are often difficult to measure. This work presents a new machine learning based modelling approach, incorporating novel physically informed feature engineering, which achieves best-in-class accuracy and reduced training time. The different features introduced are proportional to sources of machine losses and require no prior knowledge of the machine, hence the models are completely data driven. Evaluation using a standard experimental dataset shows that modelling errors can be reduced by up to 82.5%, resulting in the lowest mean squared error recorded in the literature of 2.40 K2. Additionally, models can be trained with less training data and have lower sensitivity to data quality. Specifically, it was possible to train a loss enhanced multilayer perceptron model to a mean squared error

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]

Electric machines are important devices that convert electrical energy into mechanical energy and are extensively used in a wide range of applications. Recent years have seen an increase in applications where electric motors are used. The frequent use of electric motors in noise-sensitive environments increases the requirements placed on electric motors intended for these applications, especially when compared to electric motors commonly used in industrial applications. This paper provides a comprehensive review of electric motor noise. Firstly, a brief introduction to noise is given. Then, the sources of electromagnetic noise and vibration in electric machines, including mechanical, aerodynamic and electromagnetic factors, are presented. Different methods such as analytical, numerical and semi-analytical for calculating electromagnetic force, natural frequencies and noise are also analyzed. Various methods for noise reduction are presented, including skewing, stator and rotor notching and slot opening width. Finally, noise measurement standards and procedures are described. [ABSTRACT FROM AUTHOR]

This paper describes a universal method proposed by the author for the evaluative analytical calculation of the main parameters of synchronous electrical machines, including superconducting ones. Traditional methods for analytical calculation of parameters to build a phasor diagram of electrical machines require a calculation of all dimensions of the active zone, tooth-slot zone and frontal parts of armature windings. All sizes and local states of magnetic circuit saturation are necessary for the calculation of magnetic conductivities. Traditional analytical methods use, among other things, empirical formulas and non-physical coefficients and allow one to calculate only standard machines with classic tooth-slot zones and armature winding types. As a result of drawing a phasor diagram using traditional methods, the angle between the electromotive force and voltage is calculated, which is the machine's internal parameter and has no major significance for users. The application of modern computer programs for simulation requires a preliminary analytical calculation in order to obtain all dimensions of the three-dimensional model. FEM simulation programs are expensive, require expensive high-performance computers and highly paid skilled personnel. Fast analytical techniques are also required to assess the correctness of the obtained automatic computer simulation results. The proposed analytical method makes it possible to quickly obtain all the main parameters of a newly designed machine (including superconducting ones and those of non-traditional design) without a detailed calculation of the dimensions of the tooth-slot zone and armature end-windings. The characteristic values of load angles are set according to the results of simple calculations, and the desired values, obtained via plotting, represent the inductive resistances of armature winding and inductive voltage drop across it. Results of practical significance, calculated from the voltage diagram, are as follows: the inductor's magnetomotive force necessary to maintain the nominal load voltage value, regardless of the magnitude (including double overload) and type of the connected load, or the main dimensions of the active zone. [ABSTRACT FROM AUTHOR]

This paper presents the design of a 2 MW superconducting electric machine capable of replacing a conventional regional aircraft turbine. The main objective of this work is to advance in the path towards the more-electric aircraft, by incorporating and assessing in the same design technologies such as a superconducting rotor and its cooling by means of helium at cryogenic temperatures, the skewed armature winding or the oil-flooded cooling of the stator, to obtain high specific power density and efficiency values. Although the use of these technologies is well known in the literature, no work is found to implement all of them simultaneously, which poses great challenges both for their subsequent manufacture and later performance. After showing and justifying each element of the design of the electric machine, the electromagnetic performance of the motor and of the superconducting coils is assessed, it is thermally evaluated so that it does not exceed the strict temperature limits and a mechanical analysis of the elements of the motor is also carried out. The main finding of this work is the validation of the proposed model, and that, even though the designed engine is feasible at the proposed power level, the specific power density and efficiency values would improve in the case of upscaling the engine for implementation in larger aircraft.

Finding efficient and satisfactory energy storage systems (ESSs) is one of the main concerns in the industry. Flywheel energy storage system (FESS) is one of the most satisfactory energy storage which has lots of advantages such as high efficiency, long lifetime, scalability, high power density, fast dynamic, deep charging, and discharging capability. The above features are necessary for electric vehicles (EVs), railways, renewable energy systems, and microgrids. Also, electrical machines, power electronics converters, and control systems are the cores of energy transfer in FESS. Therefore, they have a critical role in determining efficiency, power rating, power factor, cost, angular velocity, and volume of FESS. So, in this study, the FESS configuration, including the flywheel (rotor), electrical machine, power electronics converter, control system, and bearing are reviewed, individually and comprehensively. Additionally, the mentioned components have been categorized to be a guide for future research. The investigated electrical machines are compared by Finite Element Analysis (FEA). Subsequently, our laboratory’s measurement results are reviewed experimentally showing the progress in the field of FESS, such as designing robust control algorithms and an Interior Permanent Magnet-Synchronous Reluctance Machine (IPM-SynRM) to use in FESS.

Common-mode voltage and current in an electric machine are undesirable. Although the strategic placement of a common-mode inductor and dc input side capacitors may reduce the common-mode current produced by an electric drive system, the effectiveness of this mitigation is a function of machine parasitic capacitance. This engenders the need to insert another electrical component into the system to effectively mitigate the common-mode current. With this purpose, a common-mode shorting network for an inverter-based drive system is proposed in this work. This network, in conjunction with a common-mode inductor and dc input side capacitors, reduces the machine common-mode voltage and current. The proposed approach is experimentally demonstrated.

A new power system with new energy as the main body will be built. Wind power generation will become an important part of the new power system. Compared with onshore wind power, offshore wind power has become a research hotspot with the advantages of abundant wind resources, high utilization rate, close distance from power load, easy power transmission and consumption. However, with the large-scale offshore wind turbine capacity and the improvement of the proportion of wind power, its disadvantages of weak impact load resistance, weak grid friendliness, large volume and high cost are becoming increasingly prominent. In view of the above problems, this paper carries out the research on the design and modeling of double rotor double machine wind turbine generation system. The research contents include the designing the structure, analyzing the working principle, establishing the math model and proposing the control strategy. The system designed in this paper has the characteristics of strong impact load resistance, good power quality, high power grid stability and reliability, small volume, light weight and low cost.

Featured Application: The research findings can be applied in the design of generators of various vehicles, in particular synchronous homopolar generators. Electric machines with hybrid excitation have increased torque density while maintaining a wide range of speed control. This article presents the results of the optimal design of a synchronous homopolar generator (SHG) with ferrite magnets on the rotor and excitation winding on the stator for passenger cars. The use of ferrite magnets on the rotor of a synchronous homopolar generator makes it possible to use the stator surface more efficiently, which in turn increases energy efficiency and reduces the dimensions of the generator. At the same time, the excitation winding on the stator provides a reliable brushless design and the ability to control the excitation flux. The problem of long-time calculation of the three-dimensional SHG structure, which is especially relevant when using multi-iterative computer optimization, is solved by using the computationally efficient Nelder-Mead method and a simplified SHG model using two-dimensional finite element analysis. It is also clear that the low torque ripple of SHG with ferrite magnets with two stator-rotor stack combinations (SRSC) is largely provided by the fact that the torque ripples of individual SRSCs are in antiphase. The problem of considering the magnetic properties of magnetic core sections made of structural low-carbon steel is discussed. It has been found that with an increase in both the saturation level of the magnetic circuit and the magnetomotive force (MMF) of the SHG excitation winding, resistance to irreversible demagnetization of ferrite magnets on the rotor can be increased by increasing their height. In addition, it is shown that there is a significant increase in performance when using the hybrid excitation, in comparison with the conventional SHG design without magnets. [ABSTRACT FROM AUTHOR]

Additive manufacturing has enabled the processing of high silicon electrical steels which have excellent soft magnetic properties. In bulk form, core losses as a result of eddy currents would be too large to allow their use in high-frequency electrical machines, therefore strategies are needed to reduce eddy currents. Additive manufacturing affords high part complexity and provides the opportunity for cross sectional patterns within the material to limit eddy current generation. This study investigates several designs, including a novel hexagonal pattern which is shown to have the lowest eddy current loss coefficient of 0.0005, less than 25% of the bulk material which has an eddy current loss coefficient of 0.0021. Heat treatment is shown to increase the eddy current losses, demonstrating that for high-frequency machines, it may be beneficial to use the material in the as-built state. Physical samples were compared to their intended geometries, showing there are defects in these complex cross sections causing increased eddy currents when compared to simulations, but that geometrical accuracy can be improved by alternative design methodology which experimentally experiences smaller losses. These novel cross sectional designs may be implemented into an electric machine that has a 3D magnetic flux pathway enabled by additive manufacturing, affording more flexibility for electrical engineers to design new motor architectures in the pursuit of higher power density machines.

The increasing interest in employing wide-bandgap (WBG) drive systems has brought about very high power, high-frequency inverters enjoying switching frequencies up to hundreds of kilohertz. However, voltage surges with steep fronts, caused by turning semiconductor switches on/off in inverters, travel through the cable and are reflected at interfaces due to impedance mismatches, giving rise to overvoltages at motor terminals and in motor windings. The phenomena typically associated with these repetitive overvoltages are partial discharges and heating in the insulation system, both of which contribute to insulation system degradation and may lead to premature failures. In this article, taking the mentioned challenges into account, the repetitive transient overvoltage phenomenon in WBG drive systems is evaluated at motor terminals and in motor windings by implementing a precise multiconductor transmission line (MCTL) model in the time domain considering skin and proximity effects. In this regard, first, a finite element method (FEM) analysis is conducted in COMSOL Multiphysics to calculate parasitic elements of the motor; next, the vector fitting approach is employed to properly account for the frequency dependency of calculated elements, and, finally, the model is developed in EMTP-RV to assess the transient overvoltages at motor terminals and in motor windings. As shown, the harshest situation occurs in turns closer to motor terminals and/or turns closer to the neutral point depending on whether the neutral point is grounded or floating, how different phases are connected, and how motor phases are excited by pulse width modulation (PWM) voltages.

The increasingly stringent CO2 emissions standards require innovative solutions in the vehicle development process. One possibility to reduce CO2 emissions is the electrification of powertrains. The resulting increased complexity, as well as the increased competition and time pressure make the use of simulation software and test benches indispensable in the early development phases. This publication therefore presents a methodology for test bench coupling to enable early testing of electrified powertrains. For this purpose, an internal combustion engine test bench and an electric motor test bench are virtually interconnected. By applying and extending the Distributed Co-Simulation Protocol Standard for the presented hybrid electric powertrain use case, real-time-capable communication between the two test benches is achieved. Insights into the test bench setups, and the communication between the test benches and the protocol extension, especially with regard to temperature measurements, enable the extension to be applied to other powertrain or test bench configurations. The shown results from coupled test bench operations emphasize the applicability. The discussed experiences from the test bench coupling experiments complete the insights. [ABSTRACT FROM AUTHOR]

Electric motor development is a challenging task, as higher efficiency requirements and various interdependencies between different engineering domains must be considered. Established design approaches often lack the ability to address these interdependencies because they focus on specific domains and properties. Automated, multidisciplinary design approaches hold untapped potential for optimizing motors in terms of diverse requirements and advancing the development of more efficient and reliable motors. This paper presents a systematic literature review of the current state of research in the multidisciplinary design automation of electric motors. The literature basis comprises 1005 publications that are identified by a systematic internet search. The review of the existing approaches is based on twelve criteria that characterize the design automation task in general, such as knowledge representation or reasoning methods used, as well as criteria specific to electric motor design, such as domains considered and their coupling. The analysis reveals what current approaches are lacking: Consequent analysis and integration of domains, applicability of suggested methods, incorporation of established multidisciplinary design optimization (MDO) architectures, alongside the consideration of passive components in the motor. Aside from the introduction of twelve criteria for systematic charaterization of multidisciplinary design automation of electric motors, this article expands the state of the art by proposing an initial framework to establish process chains tackling the identified gaps in the review.

The multi-modal problem and high computational cost represent challenges in the optimization of electric machines owing to their highly nonlinear electromagnetic response. To overcome these challenges, this paper proposes a multi-fidelity model-based sequential optimization method in which both low- and high-fidelity models are employed in two phases. In phase 1, the reluctance network (RN) is adopted as the low-fidelity model and mainly contributes to alleviating the abovementioned challenges. To overcome the low accuracy of the RN, the optimal design is obtained using a finite element model (FEM) in phase 2. The multi-start strategy and gradient-based algorithm are utilized instead of a heuristic algorithm in all phases to avoid excessive calculations. This mutli-fidelity model concept has an originality compared to previous research that has focused on algorithm development. The effectiveness of the proposed method is validated with two examples, consisting of the TEAM workshop problem 25 and the torque ripple minimization of an interior permanent magnet synchronous motor. The optimal designs and computational time resulting from the proposed method are compared with those of the conventional method, where only a FEM is used during optimization. The results show that the proposed method is remarkable in finding superior optimal designs, while ignoring unimportant local optima. Additionally, it can save up to 90% of the computational time required by the conventional method.

Abstract The use of trigonometric polynomials as Lagrange multipliers in the harmonic mortar method enables an efficient and elegant treatment of relative motion in the stator-rotor coupling of electric machine simulation. Explicit formulas for the torque computation are derived by energetic considerations, and their realization by harmonic mortar finite element and isogeometric analysis discretizations is discussed. Numerical tests are presented to illustrate the theoretical results and demonstrate the potential of harmonic mortar methods for the evaluation of torque ripples.

Specific power, defined as the ratio of output power to total mass, is one of the generally accepted figures of merit for electrical machines. Given the growing interest in electric aircraft, developers are trying to demonstrate a high value of this indicator for their products. This paper provides an overview of the projects of electrical machines with high power density, the use of which is promising in aircraft of various dimensions. Projects of the University of Nottingham, the University of Illinois, Siemens, Yasa, and others were considered. An analysis of their technical and technological characteristics and approaches to design, manufacturing, and testing is given. [ABSTRACT FROM AUTHOR]

The increasing interest in employing wide-bandgap (WBG) drive systems has brought about very high power, high-frequency inverters enjoying switching frequencies up to hundreds of kilohertz. However, voltage surges with steep fronts, caused by turning semiconductor switches on/off in inverters, travel through the cable and are reflected at interfaces due to impedance mismatches, giving rise to overvoltages at motor terminals and in motor windings. The phenomena typically associated with these repetitive overvoltages are partial discharges and heating in the insulation system, both of which contribute to insulation system degradation and may lead to premature failures. In this article, taking the mentioned challenges into account, the repetitive transient overvoltage phenomenon in WBG drive systems is evaluated at motor terminals and in motor windings by implementing a precise multiconductor transmission line (MCTL) model in the time domain considering skin and proximity effects. In this regard, first, a finite element method (FEM) analysis is conducted in COMSOL Multiphysics to calculate parasitic elements of the motor; next, the vector fitting approach is employed to properly account for the frequency dependency of calculated elements, and, finally, the model is developed in EMTP-RV to assess the transient overvoltages at motor terminals and in motor windings. As shown, the harshest situation occurs in turns closer to motor terminals and/or turns closer to the neutral point depending on whether the neutral point is grounded or floating, how different phases are connected, and how motor phases are excited by pulse width modulation (PWM) voltages. [ABSTRACT FROM AUTHOR]