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A novel flux-switching transverse-flux permanent magnet tube linear motor (FSTFPMTLM) with oblique air-gap is proposed in this article, which combined the merits of the tube linear motor, the transverse-flux linear motor, and the switched-flux linear motor. The structure and operating principle of the FSTFPMTLM is presented first. Considering this motor has a 3-D magnetic circuit and designing the motor with high performance, this article proposes an optimization method for the FSTFPMTLM by decomposing the design of the motor into two steps to separate optimization using experimental design method. The first step is to optimize the cross-section part of the motor. After that the optimized motor is compared with the initial one by finite element method (FEM). The prototype is then manufactured and tested.

International audience; In this article, a novel five-phase fractional-slot concentrated winding (FSCW) with 20-slot/22-pole is presented. It benefits notonly the advantages of conventional FSCW but also weak space harmonics of magnetomotive force (MMF). The winding allowseliminating the first sub-order harmonic. The new layout of the winding topology is obtained by a combination of stator shifttechnique of the winding in the slots with a special coupling of the windings (star-pentagon), using winding function theory. Thehigh performances of the new winding layout are validated using the finite element method (FEM). Compared to the conventional winding, the winding factor and the total harmonic distortion (THD) of MMF are improved by 1.3% and 2.2%, respectively. With the same injection of current density, the average output torque is increased by 1% and the torque ripple is decreased by 60%.The eddy current losses in the permanent magnets (PMs) at rated speed (600 r/min) and 2100 r/min speed are improved by 67% and 56%, respectively.

The purpose of this paper is to optimize the topology of the rotor head in a Salient Pole Synchronous Generator to maximize the magnetic flux in the stator yoke and in the air gap. The generator is modelled using FE method, and the ON-OFF method is used to manage the optimization domain. Genetic Algorithm is used to find the optimal solution for the problem. The resulting topology and convergence graphs are also presented, and the results are discussed.

This paper presents an optimization method that deal with control techniques for electrical machines, in order to impose a displacement with a minimum of energy consumption. It’s a generic method; However, its application to electrical machines is complex for implementation. The present work provides the shape of the optimal solution. Moreover, a resolution technique related to the nature of the model is proposed, which facilitate the numerical resolution of costate problem. The method is applied to hybrid stepper motor and the obtained results are then analyzed.

The winding design of an electrical machine is an important task in the whole design process. This leads, for a part, to the magneto motive force which is one of the main quantities to manage for electrical machine performances. Indeed, the latter is directly linked to that of the air gap magnetic flux density and thus to the torque ripples, vibration and then noise. This paper proposes to reduce the MMF harmonic content by means of optimization process using mono-objective or multi-objective algorithms with discrete and continuous variables. For this aim, optimization algorithm is coupled with an analytical tool which enables calculating quickly the MMF harmonic content from winding parameters. A winding optimization of three different windings with the same number of pole pairs is proposed to show the suitability of this process.

Purpose For a given rotor, the study of the impact of stator MMF from different winding distributions is usually carried out using analytical model under some simplifying hypotheses to limit time computation. To get more accurate results, finite element model is thus more suitable. However, testing different combinations of stator windings with the same rotor can be tedious when considering the stator slots. Indeed, this introduces mesh constraint, reluctance variation of the air gap and possibly taking into account of the connection between stator coils. To avoid this, a current sheet supplied such to represent the stator MMF and spread all around the inner slotless stator surface can be used. In addition, such an approach can be very useful to didactically assess the effect of each winding space harmonic on machine performance separately. The purpose of this paper is to use a current sheet coupled to an external analytical tool in order to easily test different windings or to quantify the effect of a given spatial harmonic of the winding. Design/methodology/approach In the proposed approach, the current sheet supply is obtained from an analytical tool that allows determining the spatiotemporal stator MMF of any winding considered. Moreover, stator teeth height is not modelled, and only the thickness of the stator yoke is considered along with the same air gap thickness. Results with the proposed approach are compared to the real stator modelling for two different winding configurations. Last, linear and non-linear magnetic material behaviours are investigated to validate the proposed approach in term of magnetic distribution. Findings For both studied cases, results in term of local and global physical quantities show good agreement between the real stator modelling and the proposed approach. Originality/value Current sheet is used with finite element model to study the inherent effect of different winding configurations on local and global physical quantities of an AC electrical machine. The proposed approach avoids the constraints in terms of stator slot geometry and electrical circuit definition. This is very useful to quickly test different winding configurations or to isolate a specific winding space harmonic to quantify its effect on the electrical performances. This cannot be performed using classical modelling as all space harmonics are taken into account.

In this paper, a strong coupling between magnetic and electric phenomena is provided allowing to have an accurate and high-speed coupled model. A coupled circuit and magnetic model for an E-core transverse flux permanent magnet linear motor (TFPMLM) is proposed, which has an advantage linked to reducing time computing more than ten times when compared to 3-D finite-element model (FEM). Firstly, a multi-plane flexible-mesh nonlinear equivalent magnetic network (EMN) model is proposed to improve the computation efficiency as well as the high precision of the magnetic model. And a new method to define the converged iterative process is presented to further decrease the computing time. Secondly, the magnetic circuit and electric circuit are normalized into a solution matrix by introducing controlled sources and discretization methods which forms the coupled model. Then, the magnetic flux in the magnetic circuits and the current in the electric circuits are obtained simultaneously for each time step. The characteristics such as the air-gap flux density distribution, output thrust force waveforms and the phase currents are analyzed by the proposed coupled model. The modeling approach is approved by comparison with the 3-D FEM model. Finally, the proposed model is validated through the experimental setup with the machine prototype.

Cet article brosse un panorama de la CAO en genie electrique. Une vision globale de la conception est d’abord introduite avant de presenter le processus iteratif du prototypage virtuel avec quelques-unes des approches de modelisation classiquement utilisees pour evaluer les performances des convertisseurs electriques. L’accent est mis sur la necessite de tenir compte de l’environnement d’utilisation du dispositif a concevoir et des differentes physiques mises en jeu ainsi que sur les strategies d’optimisation types dans le processus de conception. Un eclairage est apporte sur les effets des procedes de fabrication, notamment pour distinguer le prototype virtuel du prototype reel. Enfin, la presentation de quelques axes de developpements futurs dans le domaine de la CAO cloture l’article.

The electromagnetic noise generated by the Maxwell radial pressure is a well-known consequence. In this paper, we present an analytical tool that allows air gap spatio-temporal pressures to be obtained from the radial flux density created by surface permanent magnet synchronous machines with concentrated winding (SPMSM). This tool based on winding function, a global air-gap permeance analytical model and total magnetomotive force product, determines the analytical air-gap spatio temporal and spectral radial pressure.We will see step-by-step their impacts in generating noise process. Also two predictive methods will be presented to determine the origin of the lows radial pressure orders noise sources. The interest lies in keeping results very quickly and appropriate in order to identify the low order electromagnetic noise origin. Then through an inverse approach using an iterative loop a new winding function is proposed in order to minimize radial force low order previously identified and chosen.

Multi-objective optimization with finite-element model (FEM) for the optimal design of electromagnetic devices is a complex task and also time costly. Output space mapping (OSM) techniques allow having an affordable computation cost with a minimum number of computationally expensive FEM evaluations. In this paper, a bi-objective Kriging adapted OSM, an original space-mapping technique based on adaptive nonlinear corrective projection, is proposed. First, the proposed technique is validated using a mathematical test function; Second, it is applied on a three-phase brushless dc motor, which is represented through two modeling levels: 1) coarse (analytical model) and 2) fine (2-D FEM). An advantage of this new technique is its ability to make the coarse model converge effectively toward the fine model.

International audience; This article analyzes and highlights the impact of an iron loss model on temperature estimation within a multi-physical model of a radial-flux permanent-magnet (PM) synchronous machine (PMSM) for traction application. Three iron loss models have been compared in terms of computing time and accuracy within the machine torque-speed plane. This study underlines the iron loss calculation impact on the temperature estimation in the PMSM in relation with the required performances.

In this paper, the air-gap flux density monitoring is proposed to detect rotor faults in a Salient Pole Synchronous Generator (SPSG). A manufactured SPSG of 15 MVA and Finite Element (FE) simulations are used to replicate a reliable signature of the machine. The method aims at combining the harmonic content of power spectrum and polar representation of the air-gap flux density to detect possible rotor failure. The application of the proposed method is performed through FE simulations including different rotor faults such as rotor inter-turn short circuit, static and dynamic eccentricity faults.

Purpose The purpose of this paper is to propose a methodology to seek the optimal topology of electromagnetic devices using the density method while taking into account the non-linear behaviour of ferromagnetic materials. The tools and methods used are detailed and applied to a three-dimensional (3D) electromagnet for analysis and validation. Resulting topologies with and without the non-linear behaviour are investigated. Design/methodology/approach The polynomial mapping is used with the density method for material distribution in the optimisation domain. To consider the non-linear behaviour of the materials, an analytical approximation based on the Marrocco equation is used and combined with the polynomial mapping to solve the problem. Furthermore, to prevent the occurrence of intermediate materials, a weighted sum of objectives is used in the optimisation problem to eliminate these undesired materials. Findings Taking into account the non-linear materials behaviour and 3D model during topology optimisation (TO) is important, as it produces more physically feasible and coherent results. Moreover, the use of a weighted sum of objectives to eliminate intermediate materials increases the number of evaluations to reach the final solution, but it is efficient. Practical implications Considering non-linear materials behaviour yields results closer to reality, and physical feasibility of structures is more obvious in absence of intermediate materials. Originality/value This work tackles an obstacle of TO in electromagnetism which is often overlooked in literature, that is, non-linear behaviour of ferromagnetic materials by proposing a methodology.

PurposeThis paper aims to investigate three low-evaluation-budget optimization techniques: output space mapping (OSM), manifold mapping (MM) and Kriging-OSM. Kriging-OSM is an original approach having high-order mapping. Design/methodology/approachThe electromagnetic device to be optimally sized is a five-phase linear induction motor, represented through two levels of modeling: coarse (Kriging model) and fine.The optimization comparison of the three techniques on the five-phase linear induction motor is discussed. FindingsThe optimization results show that the OSM takes more time and iteration to converge the optimal solution compared to MM and Kriging-OSM. This is mainly because of the poor quality of the initial Kriging model. In the case of a high-quality coarse model, the OSM technique would show its domination over the other two techniques. In the case of poor quality of coarse model, MM and Kriging-OSM techniques are more efficient to converge to the accurate optimum. Originality/valueKriging-OSM is an original approach having high-order mapping. An advantage of this new technique consists in its capability of providing a sufficiently accurate model for each objective and constraint function and makes the coarse model converge toward the fine model more effectively.

International audience

Using the finite-element model (FEM) to achieve the optimal design of electromagnetic devices is a complex and time-consuming process. Space-mapping techniques reduce computation cost by aligning two models with different granularities, namely, a coarse model and a fine model. In this paper, Kriging output space mapping (OSM), an original space-mapping technique based on adaptive nonlinear corrective projection, is proposed and compared with a conventional OSM technique. The device for optimal sizing is a five-phase linear induction motor, which is represented through two modeling levels: 1) coarse (Kriging model) and 2) fine (2-D FEM). An advantage of this new technique is its ability to provide a sufficiently accurate model for each objective and constraint function and make the coarse model converge effectively toward the fine model.

Magneto Motive Force is an important quantity to analyze winding harmonic effect. Indeed, the latter is directly linked to that of the air gap magnetic flux density and thus to the torque ripples, vibration and then noise. This paper proposes to reduce the MMF harmonic content by means of optimization process using mono-objective or multi-objective algorithms with discrete and continuous variables. To this aim, optimization algorithm is coupled with an analytical tool which allows quickly calculate the MMF harmonic content from winding parameters. A winding optimization is proposed to show the use of this method.

The purpose of this paper is to optimise the topology of the rotor head shape in a Salient Pole Synchronous Generator so that it maximises the flux in the stator yoke and the air gap. The generator is modelled using FE method. An ON-OFF method is used to manage the optimisation domain, and Genetic Algorithm to find the optimal solution. The resulting topology and convergence graphs are also presented.

This paper presents an optimization method that allows to find the electrical machine control, in order to impose a displacement with a minimum energy consumption. This is a generic method. However, its application to electrical machine is complicated to implement. In this paper, the optimal solution form is proposed for the studied case. Moreover, in order to facilitate the numeric resolution of the auxiliary problem, a technique related to the model nature is proposed. An example with a hybrid stepper motor is presented.

This paper deals with a structural optimization to maximize the no-load flux control capability of a double excitation synchronous machine (DESM). The air-gap flux in this machine type can be regulated by controlling the field currents. In this paper, this curve in the no-load condition is referred to as the flux control range (FCR). Maximizing the gap between the minimum-flux and maximizing the maximum-flux points of this curve is targeted to improve the controlling effectiveness of the field windings, and reduce field winding’s copper losses. This gap is affected by two factors: the magnetic saturation and thermal limits of the machine. Thermal analyses are rarely focused for the DESM type in the literature. The contribution of this paper is to maximize the FCR gap taking into account the thermal limitation. In addition, a general guide for the DESM design will be also discussed.

This paper presents a global optimization approach aiming to improve the energy efficiency of electrical machines. The process is made on a hybrid stepper motor allowing to simultaneously optimize design and command. This approach is axed around Pontryagin's maximum principle, which is applied to a magnetodynamic model based on permeances network model. The originality of the proposed approach is to obtain in the same process, the minimization of the energy by optimal control and the minimization of the energy by optimal sizing.

The aim of this paper concerns the design with these targets for low power motors that offer a good compromise in terms of performance: speed, torque, current, and noise linked to the radial forces. Different low power machines and topologies are studied with the same constraints in term of volume for the same value of the torque. The study is carried out on a PMSM with surface permanent magnet ‘SPM’ and with insert permanent magnet ‘IPM’. In order to reduce the cost, a synchronous reluctance machine ‘SynRM’ is also designed and studied. 2D and 3D Finite Element modeling are used to compare the performance of the three different topologies. In addition, the best solutions are realized and tested.

Magneto motive force is a key quantity of the energy conversion in the electrical machines. Its harmonic content is important as it leads to the one of the magnetic flux density in the air gap. Thus, whatever the winding of the machine, a first step consists to study the winding function in order to analyze the magnetic flux density. Many tools already exist to tackle this point but generally they use some methods like Star of slots or matrix representation and the harmonic content is obtained by a Fast Fourier Transform of the total winding function. In the present paper, we propose to build up the winding function using elementary patterns whose harmonic contents are used to reach the one of the whole function using a geometrical construction. This approach is quite fast and allows easy analyzing in order to reduce or cancel a magnetic harmonic.

This paper provides a comparison of iron loss models submitted to synchronous generator flux density waveforms. The purpose is to highlight which model is recommended to be used during the design process of generator. Several measures on the Epstein frame have been performed with realistic flux density waveforms. These waveforms ensure a fair comparison to the application. Some useful conclusions on the iron loss models are obtained for use in the design process.

This paper studies different low power machines and topologies with the same constraints in term of volume for the same value of the torque. The aim of this paper concerns the design with these targets for low power motors that offer a good compromise in terms of performance: speed, torque, current, and noise linked to the radial forces. The study is carried out on a PMSM with surface permanent magnet ‘SPM’ and with insert permanent magnet ‘IPM’. In order to reduce the cost, a synchronous reluctance machine ‘SynRM’ is also designed and studied. 2D and 3D Finite Element modeling are used to compare the performance of the three different topologies.

A novel transverse-flux permanent magnet linear motor (TFPMLM) named as double-sided double-excited one is proposed in this paper. First, the operational principle and structural advantages of the TFPMLM are presented. Then, the 3-D magnetic circuit structure of the TFPMLM is simplified equivalently into a 2-D one in order that Schwarz–Christoffel (SC) mapping method can be adopted to analyze the motor’s magnetic field and characteristics. Then, the air-gap flux density distribution, back voltage and force waveforms when at no-load and at load are calculated by the SC mapping method and 3-D finite-element method, respectively, for a prototype linear motor, The results from the two methods coincide much better with each other. At last, influences of magnet shape on the cogging force are studied by the SC method.

This paper proposes a method to the model constraints from different models to run an optimization over models with different granularities. Through machine learning, the proposed method has proven to be able to accurately map the constraints and minimize the number of call to the model. It handles both continuous and discrete variables and mixes design rules to statistic approach to create a surrogate of the model.

International audience; I N [1], an error in Fig. 2 in Section II-B is corrected. In the original figure, Fig. 2(b) was exactly the same as Fig. 2(a). The correction is shown here. Fig. 2. RN model of the prototype. (a) First part. (b) Second part. (c) More details about elements in the axial direction.

International audience; This paper presents a comparison between a Double Excitation Synchronous Machine (DESM) and a Permanent Magnet Synchronous Machine (PMSM). Optimal designs of both machine types are compared regarding different constant power speed ranges (CPSR). The optimization objectives are to minimize the active material cost and losses. Results show that the DESM is more advantageous over the PMSM counterpart in loss saving at a wide CPSR, and the PMSM is capable of reducing the machine cost.

International audience; This paper presents performance improvements of a double excitation synchronous motor by using a reluctance network (RN). The distinguishing feature of the double excitation principle is to use permanent magnets with high energy, while air-gap flux is flexibly controlled by field windings. Therefore, the first contribution of this paper focuses on maximizing air-gap flux range control. Second, an approach for torque ripple reduction is proposed by directly modifying air-gap flux according to the instantaneous torque profile. The achieved resultant torque stays almost constant for a case study. The validity of the RN method is examined by comparisons with 3-D finite element and experimental results for several machines.

Purpose – The purpose of this paper is to develop an optimal approach for optimizing the dynamic behavior of incremental linear actuators. Design/methodology/approach – First, a parameterized design model is built. Second, a dynamic model is implemented. This model takes into account the thrust force computed from a finite element model. Finally, the multiobjective optimization approach is applied to the dynamic model to optimize control as well as design parameters. Findings – The Pareto front resulting from the optimization approach (or the parallel optimization approach,) is better than the Pareto, which is obtained from the only application of MultiObjective Genetic Algorithm (MOGA) method (or parallel MOGA with the same number of optimization approach objective function evaluations). The only use of MOGA can reach the region near an optimal Pareto front, but it consumes more computing time than the multiobjective optimization approach. At each flowchart stage, parallelization leads to a significant reduction of computing time which is halved when using two-core machine. Originality/value – In order to solve the multiobjective problem, a hybrid algorithm based on MOGA is developed.

Purpose – Discrete highly constrained optimization of induction machine taking into consideration two objective functions: efficiency and total costs of production. The paper aims to discuss these issues. Design/methodology/approach – Interactive and semi-interactive interval-based optimization methods were used. Two concepts of multi-objective discrete optimization were proposed. Findings – Proposed methodology and algorithms allow decision maker (DM) participate in the process of optimal design and therefore decrease the total time of optimization process. The search procedure is straightforward and it does not require special skills of DM. Presented methods were successfully versified for the problem of optimal design with discrete variables. Research limitations/implications – Three interval algorithms suitable for inverse problems are researched and verified. It generally can be used for multi-objective problems. The dominance principles for interval boxes are showed in the paper. Proposed algorithms are based on the idea of hybridization of exact and evolutionary methods. Practical implications – Proposed approaches were successfully implemented within computer-aided application which is used by manufacturer of high power induction machine. Originality/value – The concept of pareto-domination using the interval boxes can be treated as original. The paper researched several elimination rules and discusses the difference between different approaches.

Purpose – The purpose of this paper is to present an application of a multidisciplinary multi-level design optimization methodology for the optimal design of a complex device from the field of electrical engineering throughout discipline-based decomposition. The considered benchmark is a single-phase low voltage safety isolation transformer. Design/methodology/approach – The multidisciplinary optimization of a safety isolation transformer is addressed within this paper. The bi-level collaborative optimization (CO) strategy is employed to coordinate the optimization of the different disciplinary analytical models of the transformer (no-load and full-load electromagnetic models and thermal model). The results represent the joint decision of the three distinct disciplinary optimizers involved in the design process, under the coordination of the CO's master optimizer. In order to validate the proposed approach, the results are compared to those obtained using a classical single-level optimization method – sequential quadratic programming – carried out using a multidisciplinary feasible formulation for handling the evaluation of the coupling model of the transformer. Findings – Results show a good convergence of the CO process with the analytical modeling of the transformer, with a reduced number of coordination iterations. However, a relatively important number of disciplinary models evaluations were required by the local optimizers. Originality/value – The CO multi-level methodology represents a new approach in the field of electrical engineering. The advantage of this approach consists in that it integrates decisions from different teams of specialists within the optimal design process of complex systems and all exchanges are managed within a unique coordination process.

Purpose– The purpose of this paper is to apply some surrogate-assisted optimization techniques in order to improve the performances of a five-phase permanent magnet machine in the context of a complex model requiring computation time.Design/methodology/approach– An optimal control of four independent currents is proposed in order to minimize the total losses with the respect of functioning constraints. Moreover, some geometrical parameters are added to the optimization process allowing a co-design between control and dimensioning.Findings– The optimization results prove the remarkable effect of using the freedom degree offered by a five-phase structure on iron and magnets losses. The performances of the five-phase machine with concentrated windings are notably improved at high speed (16,000 rpm).Originality/value– The effectiveness of the method allows solving the challenge which consists in taking into account inside the control strategy the eddy-current losses in magnets and iron. In fact, magnet losses are a critical point to protect the machine from demagnetization in flux-weakening region.

For the design and analysis of a linear electrical motor, an analytical solution of electric and magnetic fields is barely achieved with the required accuracy, due to the end and edge effects, and the nonlinear characteristic of the materials. Optimal design with the finite element models (FEM) is often expensive, in terms of the computation time. The space-mapping techniques allow having an affordable computation cost with a minimum number of computationally expensive FEM evaluations. In this paper, based on a kriging model, a 2D FEM and a 3D FEM, a 3-level adapted output space-mapping technique is employed. The results show that the proposed algorithm allows saving a substantial amount of computation time compared to conventional 2-level output space-mapping technique.

Modeling the dynamic behavior of electrical machines involves several fields of physics, such as electromagnetics, electronics, mechanics, thermodynamics and acoustics. Multi-physics lumped models are applied to an inverter-fed permanent magnet synchronous machine. These models are coupled and fully parameterized to optimize the machine for traction appli- cations. A particle swarm optimization algorithm is used to obtain general tendencies and different design rules. The objective is to provide a decision-making tool using lumped models to design permanent magnet synchronous motors. In this paper, we focus on electromagnetic noise, and average and ripple electromagnetic torque. The magnetic model, a permeance network, provides a good compromise between accuracy and computing time.

International audience; The presented paper proposes a topology optimisation methodology based on the density-based method SIMP, and applied to a numerical example to validate the former. The approach and methodology are detailed, and the results for a 3D basic electromagnetic example are presented. The non-linear B(H) curve is also taken into account.

This paper deals with a methodology developed for fast and accurate dynamic modeling of Hybrid Stepper motors. The proposed method is based on reluctance network magnetostatic modelling validated by finite element simulations.

An analysis of Hybrid Excitation Synchronous Generator (HESG) topologies for a direct drive wind turbine is investigated. Through an optimization process, the topologies of HESG are compared regarding the cost and the total losses. The optimizations are performed at the nominal on-load operating point of the generator. The trade-offs between each topology are analyzed according to a set of Pareto fronts. An instrumented prototype of 900kVA approves the design process. Finally, the best Pareto optimal solutions are compared during an experimental operating cycle of the direct drive wind turbine. The efficiency improvement emphasizes the interest of the design by optimization.

This paper presents findings from an optimal design study on a switched reluctance machine operating in both motoring and generating modes as automotive integrated starter/alternator. The design optimization approach employs an analytical lumped-parameter modelling of the switched reluctance machine in motor and generator operations, which is refined by finite-element magnetic field analysis of the machine and then implemented in MATLAB/Simulink environment. The objective function of the design optimization problem is the maximization of the average electromagnetic torque of the machine for motor operating mode under constraints on rotor speed, energy efficiency and torque ripple. Steady-state and dynamic simulation results for the optimally-designed switched reluctance machine in motoring and generating modes, as part of automotive integrated starter/alternator operation cycle, are also provided.

Purpose The purpose of this paper is to compare two design optimization architectures for the optimal design of a complex device that integrates simultaneously the sizing of system components and the control strategy for increasing the energetic performances. The considered benchmark is a battery electric passenger car. Design/methodology/approach The optimal design of an electric vehicle powertrain is addressed within this paper, with regards to performances and range. The objectives and constraints require simulating several vehicle operating points, each of them has one degree of freedom for the electric machine control. This control is usually determined separately for each point with a sampling or an optimization loop resulting in an architecture called bi-level. In some conditions, the control variables can be transferred to the design optimization loop by suppressing the inner loop to get a mono-level formulation. The paper describes in which conditions this transformation can be done and compares the results for both architectures. Findings Results show a calculation time divided by more than 30 for the mono-level architecture compared to the natural bi-level on the study case. Even with the same models and optimization algorithms, the structure of the problem should be studied to improve the results, especially if computational cost is high. Originality/value The compared architectures bring new guidelines in the field optimal design for electric powertrains. The way to formulate a design optimization with some inner degrees of freedom can have a significant impact on computing time and on the problem understanding

In traction application, the electric motor design methodology is not trivial. This paper presents a design approach using rated point. Based on a 2D finite element model, design optimization of a double-sided linear induction motor is achieved using an efficient global optimization algorithm.

International audience; — This paper presents an analysis of low the space order of the air-gap radial Maxwell pressures in Surface Permanent Magnet Synchronous Machines (SPMSM) with fractional slot concentrated windings. The air-gap Maxwell pressures result from the multiplication of the flux density harmonics due to magnetomotive forces and permeance linked to the magnet, the armature, and the stator slots and their interactions. One low space order is selected and different approaches are compared to determine the origin of this pressure. First, an analytical prediction tool ACHFO (Analytical Calculation of Harmonic Force Orders) is issues to calculate the space and time orders of these magnetic pressure harmonics while identifying their origin in terms of interactions between magnet, armature and teeth effects. Additionally, the analytical prediction of ACHFO is compared with the flux density convolution and finite element approaches. The main advantage of our tool is the speed of computation. Finally, an experimental Operational Deflection Shape measurement (ODS) is performed to show the deflection shape of the low space order selected. Keywords— fractional slot concentrated winding, air-gap radial Maxwell pressures; lowest space order; analytical tool; convolution analysis; operational deflection shape (ODS).

PurposeThe purpose of this paper is to present two optimization methodologies based on interval branch‐and‐bound algorithm.Design/methodology/approachThese techniques decrease the total time of computation, even in spite of discrete nature of some of the design variables. Computational experiments performed on multivariable optimization problem reveal great accuracy and technical validity of developed approaches. As an example, the optimal design of the induction machine (IM) was treated, where the aim was to find the set of the most efficient and, at the same time, cheapest in the manufacturing configurations.FindingsIn this paper, two approaches were developed for resolving the problem of optimal design of IM with discrete variables. The strategy of constructing the meta‐models is utilized and put in practice. The methods show relatively high efficiency and robustness of obtained results.Originality/valueThese approaches are the core technics of the developed industrial application, which help identify the set of optimal configurations of IM with the criteria of optimality such as total cost of manufacturing and the efficiency of IM.

PurposeThe purpose of this paper is to present a low evaluation budget optimization strategy for expensive simulation models, such as 3D finite element models.Design/methodology/approachA 3D finite element electromagnetic model and a thermal model are developed and coupled in order to simulate the linear induction motor (LIM) to be conceived. Using the 3D finite element coupling model as a simulation model, a multi‐objective optimization with a progressive improvement of a surrogate model is proposed. The proposed surrogate model is progressively improved using an infill set selection strategy which is well‐suited for the parallel evaluation of the 3D finite element coupling model on an eight‐core machine, with a maximum of four models running in parallel.FindingsThe proposed strategy allows for a significant gain of optimization time. The 3D Pareto front composed of the finite element model evaluation results is obtained, which provides the designer with a set of optimal trade‐off solutions for him/her to make the final decision for the engineering design.Originality/valueAn infill set selection strategy is proposed, which allows the parallel evaluation of the finite element model, and at the same time guides the progressive construction of an improved surrogate model during the multi‐objective optimization run. The paper may stand as a good reference for researchers/engineering designers who have to deal with optimal design problems implying costly simulation models.