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This paper attempts to present a quasi-3D finite element method technique for modeling and analyzing tubular linear permanent magnet machines (TLPM) with translator eccentricity. Normal tubular linear machines can be modeled effectively using 2D axisymmetric models, but with the introduction of the eccentricity factor into the geometry the axis symmetry is no longer valid, and hence 3D modeling techniques become the only way for studying the machine. However, sometimes 3D modeling can become time-consuming and requires a huge amount of resources especially for non-linear problems, so the interest in modeling techniques that can represent the problem at hand with less computation time and relatively accurate results is high. A quasi-3D technique was specifically developed to be able to represent the eccentricity in TLPMs. The finite element method (FEM) was used for modeling. Eccentricity analysis has been carried on two different TLPM structures using the proposed quasi-3D, and the results from the quasi-3D model were compared to those obtained using the 3D FEM model. Both the open circuit and the on-load operating conditions were studied with the magnetic saturation taken into account. The behavior and the accuracy of the proposed model varied between the two studied structures and for the different operating conditions, and with very low computation time and cost the results obtained from the quasi-3D model were satisfactory in general except for certain cases.

Purpose This paper aims to develop a new quasi-three dimensional (3D) analytical model devoted to the study of nonlinear transient magneto-thermal coupled problems in permanent magnet (PM) transverse flux induction heating device (TFIHD). Design/methodology/approach The presented work is based on analytical development of strongly coupled problem, including electromagnetic and thermal boundary problems. The electromagnetic problem is first solved by using the separation variables method to evaluate the induced currents in the nonmagnetic plate and the resulting power density loss distribution. The plate temperature profile is then obtained thanks to strong involvement of this magnetic model in a new analytical thermal model combining the separation of variables method and the Green’s functions transient regime analysis method. The coupled model is then used in a simulation procedure of the magneto-thermal process allowing taking into account the workpiece electrothermal nonlinear properties. The developed coupled model is validated by computing the performances of the studied PM TFIHD and comparing them to those obtained by finite element simulations. Finding An efficient transient quasi-3D magneto-thermal analytical model is developed allowing rapid analysis of PM induction heating for core heating of parallelepiped parts. The developed model also allows fast and accurate simulations of nonlinear and transient three dimensional (3D) magneto-thermal phenomena for planar induction heaters. Research limitations implications The developed quasi-3D magneto-thermal analytical model is limited to design induction heating devices of planar structure with PM inductors. Originality/value A new transient quasi-3D magneto-thermal analytical model accounts for non-linearity and edge effect and helps to fast study and fast design of linear permanent magnet induction heating device.

This paper presents the design of a hybrid excited flux switching Vernier machine. This machine is designed to serve in renewable energy conversion applications, such as a wind turbine generator, or tidal turbine generator. After introducing this original structure, a design based on finite element models is conducted. The specifications correspond to relatively low power direct drive wind or tidal turbine applications. The rated power is set to 10 kW, with a rated speed of 300 rpm. Mainly the electromagnetic design is presented. Aspects related to the realization of a prototype are also presented, and an experimental study is included.

International audience; The aim of this paper is to assess the efficacy of non-conformal meshing in mesh-based generated reluctance network modeling. A representative semi-numerical example is introduced to demonstrate the possibilities and accuracy offered by a non-conformal meshing. In a conformal mesh, two reluctance block elements share the same branch. This makes the computation faster and more accurate but is not convenient for motion processing or mesh relaxation and it does not solve the air-gap modeling problem (rotor/stator connectivity). To solve this, different approaches are used. The interpolation approach developed in this paper aims to render motion processing independent of discretization. This approach is also applied to couple different meshes (spatial discretization) and makes it possible to connect a lumped parameter model to a meshed one. The model is divided into independent zones that are connected via the interpolation coupling. Several reluctance network (RN) non-conformal meshes are presented and global quantities are compared to a fine-meshed finite-element model. Magnetic saturation is considered in the iron parts. Comparisons are provided under open-circuit and on-load configurations for flux linkage and force. The main advantage is to overcome the limitations of generic RN for which the movement modeling requires remeshing at each position. The drawbacks of the method are the increased number of variables (additional interface nodes) and a certain loss of accuracy due to the interpolation function order.

This paper presents an overview of the emerging trends in the development of electrical generators for large wind turbines. To describe the developments in the design of electrical generators, it is necessary to look at the conversion system as a whole, and then, the structural and mechanical performances of the drive train need to be considered. Many drive train configurations have been proposed for large wind turbines; they should ensure high reliability, long availability and reduced maintainability. Although most installed wind turbines are geared, directly driven wind turbines with permanent magnet generators have attracted growing interest in the last few years, which has been in parallel to the continuous increase of the per unit turbine power. The aim of this work is to present the recent commercial designs of electrical generators in large wind turbines. Both the strengths and weaknesses of the existing systems are discussed. The most emerging technologies in high-power, low-speed electrical generators are investigated. Furthermore, a comparative analysis of different electrical generator concepts is performed, and the generators are assessed upon a list of criteria such as the mass, cost, and mass-to-torque ratio. Within the framework of these criteria, it may help to determine whether the electrical generator is technically feasible and economically viable for high-power wind turbines. Finally, this review could help to determine suitable generators for use in large and ultra-large wind energy systems.

This paper presents a literature review of relevant contributions found in the literature concerning the end effects with a focus mainly on linear permanent magnet synchronous machines. This work presents a classification of the obtained information to classify the end effects and provides essential information for its understanding, categorization, modeling, mitigation, and control. The causes and consequences of the end effects are presented, according to the geometrical structure. Additionally, the main approaches for end effects modeling are discussed. Also, several existing techniques for mitigation of consequences of end effects are presented, considering changes in the machine geometry or in the electromagnetic structure, and electronic compensation using control techniques. The control of linear machines accounting for end effects, and compensation to achieve better performance to mitigate negative impacts on machine characteristics are also addressed.

Permanent magnet flux switching machines are gaining more and more interest due to their relatively good characteristics. Indeed, the presence of all magnetic field sources in the stator (armature windings, permanent magnets and/or field windings), which implies a completely passive rotor, makes it suitable for a large variety of applications [1] [2]. Different flux switching machines topologies have been studied in scientific literature. In this contribution, a relatively new modeling approach [3] based on the coupling of mesh based generated reluctance networks (MBGRN) and analytical models (AM), based on the formal solution of Maxwell’s equations, is used for the accurate prediction of cogging force of a linear tubular flux switching machine. This type of machines could be favorably used in oceanic renewable energy conversion. Figure 1(a) illustrates how the two approaches are combined for the case of a tubular linear flux switching structure. In this example the analytical solution is used for modeling the mechanical air-gap, and inner and outer airs, and the RN method is used to model the moving and static armatures. In order to have a more generic approach, the stator and moving armatures are modeled using mesh based generated reluctance network (MBGRN) technique [3]. This technique, as classical RN method, can be used with a minimum number of reluctances for regions where flux tubes are not highly affected by topology changes. As for finite elements analyses (FEA), the studied domain in MBGRN should be finely meshed in some regions (air-gap for example) and coarsely meshed in other regions. However, in contrast to FEA, the mesh relaxation in MBGRN can be done more easily conducting to reduced system matrix dimensions, and consequently reduced computation time. Indeed, while in FEA two adjacent elements should share an edge, it is no more necessary for RN method, as illustrated in Fig. 1(b). This new modeling approach has been used to analyze the performance of different electromagnetics devices (2D and 3D) [3]–[7]. In this contribution, this technique is used for the computation of cogging force of a linear tubular flux switching permanent magnet structure, something which has never been reported yet, to the best of our knowledge, in scientific literature. The goal is to further extend the investigation of this technique for the computation of relatively sensitive quantities, such as the cogging force, in more complex structures. Another goal is to highlight advantages of HAM as compared to other modeling techniques, and more particularly FEA, in order to obtain reduced order equations system [8] [9].

Numerical methods and mostly finite element analysis (FEA) are popular in electromagnetic modeling because they are standardized methods and because of the availability of a large number of commercial software. However, the computation time may be prohibitive, especially for 3D models. Analytical models are fast but restricted in terms of magnetic saturation evaluation and geometry complexity. Magnetic Equivalent Circuits (MEC) are an excellent compromise as they are fast and take into account magnetic saturation. They are not as generic as FEA and if parameters vary, MEC models have to be readjusted [1–6]. Thus, model development durations are longer for MEC than for FEA. For more genericity, authors in [7–9] have demonstrated the equivalence between the equations of reluctance network (RN) and FEA method and the possibility to form RN matrix system by means of FEA. This paper presents the load analysis of a Permanent Magnet Linear Machine (PMLM) as a case study for a direct flux tube MEC method using an automatic Mesh Based Generated Reluctance Network (MGRN). The aim is to show that it is possible to quickly build a semi-numerical model of studied structures with an automatically generated MEC with accurate results on global and local quantities. Comparisons of iron losses evaluated by the use of the MGRN model show that results are in a very good agreement with those obtained byAnsys-Maxwell FEA [10] used as a reference. This approach can be used in a tool that allows the automated processing of an arbitrary geometry providing an accurate model in a shorter amount of time than needed for building a dedicated model. MESH BASED GENERATED RELUCTANCE NETWORK Geometry is discretized in a number of bidirectional elementary reluctance blocks (Fig. 1). The model is divided into zones according to geometry and material proprieties. Discretization can be made finer or coarser according to the desired precision. Central nodes of element blocks are connected via their branches. The advantage of using bidirectional block elements is that no previous knowledge of flux paths is necessary. Each mesh of the network of the final MEC will describe a possible path for flux to go through. The second advantage is to have access to normal and tangential components of local quantities such as flux density and magnetic field. Thus, forces can be evaluated using the Maxwell stress tensor and iron losses by means of Bertotti model [11]. Scalar magnetic potential is used to formulate and solve the nodal based matrix equation: $[\mathrm{U}] =[\mathrm{P}] ^{-1} [\Phi_{s}][\mathrm{P}]$ Permeance matrix [U] Scalar magnetic potential in each node $[\Phi_{s}]$ Sum of flux sources for each node n Total number of nodes The approach for solving the equation system as well as PMLM proprieties are given in [12]. A non-linear B-H curve is used for the ferromagnetic material and saturation is addressed with an iterative method as the value of permeability is adjusted in every ferromagnetic block element till convergence of the algorithm. The framework for space discretization, boundary conditions and PM sources assignment are explained in [13]. The PMLM is supplied with a 3-phase sinewave current and distribution of sources of magneto-motive force (MMF) due to coil currents is determined at each step. Fig 1 illustrates the geometry of the PMLM and the MMF distribution.Sources distribution MMF sources due to PM need to be placed on the branches of the magnetization direction (y axis) in the elements through all layers of the PM zones. Similarly, MMF sources due to coil currents are distributed on all elements of the teeth and slots. Total MMF according to position (along the x axis) is the sum of the MMF created by each coil. The ratio (height of element block to height of coil zone) is used to weight the MMF sources on each branch in each block of the winding zone (Fig. 1): mmf elem =(1/ 2)×E h Z h )× e(x node )e Total mmf according to position $\mathrm{x}_{node}$ Position of the central node of block mmf $_{elem}$: MMF on the branch of the block E h Element height Z h Zone height Saturation The permeability in the reluctances of the blocks in the ferromagnetic parts is initialized with the linear part of the B-H curve. Convergence criteria is magnetic energy in each block as a product of flux density and magnetic field at each step is compared to the one of the previous iteration till the difference no longer exceeds a pre-defined value. At each displacement step, the magnetic permeability value of the block elements are those of the previous magnetic state in the whole model i.e. the previous displacement step. \textit{Motion} A relative moving zone is defined including mover, PM and lower airgap region. The airgap is discretized in a way that the desired movement step is equal to the size of an element block in the airgap. This avoids non-conformal meshing problems and makes it easier to handle changes in matrix topology. \textit{Iron losses} The total iron losses In the MGRN model are calculated in post-processing and are the sum of hysteresis losses, eddy current and excess losses as shown in the equation: $\mathrm{P}= \mathrm{k}_{h} \quad f \mathrm{B}_{m}^{2} \quad + (\pi \sigma \mathrm{d}^{2}f^{2}/ 6 ) \int($ dB$/ \mathrm{d}\unicode{0x03B8} ) ^{2} \mathrm{d}\unicode{0x03B8} + (\pi \sigma \mathrm{d}^{2}f^{2}/ 6 ) \int\vert$ dB$/ \mathrm{d}\unicode{0x03B8} \vert ^{1.5} \mathrm{d}\unicode{0x03B8}$ Flux density values in each node of each reluctance block element are evaluated in the MGRN model using the same B(H) curve and material proprieties as implemented in the Ansys-Maxwell FEA model. Fig 2 shows comparisons of total iron losses (in all ferromagnetic parts i.e. stator and mover) vs frequency for the MGRN and the FEA models used as a reference at $\mathrm{I}_{max}=5\mathrm{A}$. It is shown that the results are in very good agreement.

Purpose This work aims to study a new design of linear permanent magnet transverse flux induction heating devices of nonmagnetic parallelepipedic workpiece. In these topologies, the permanent magnet inductor produces a static magnetic field, and the workpiece to be heated is subjected to a linear movement. To study the magnetothermal process, a new analytical coupling method between the magnetic and thermal phenomena is developed. This analytical model described in this study takes into account the variation of the physical properties of the heated workpiece. The analytical results are compared with good agreement to those issued from finite elements simulations, as well as those issued from measurements on an actual prototype. Design/methodology/approach The research methodology is based on analytical development of coupled problem, including the electromagnetic and thermal boundary problems. A strongly coupled magneto-thermal analytical model is developed; the time dependent magnetic problem is first solved by using the separation of variables method to evaluate the induced currents in the nonmagnetic plate and the resulting power density loss distribution. The plate temperature profile is then obtained, thanks to strong involvement of this magnetic model in a new analytical thermal model based on a synergy of separation of variables method and Green’s function transient regime analysis method. Findings The results show that an efficient transient magneto-thermal analytical model was developed allowing fast analysis of permanent magnet induction heater for deep heating of parallelepipedic workpieces. Developed model allows also fast and precise simulations of nonlinear and transient magneto-thermal phenomena for different types of permanent magnet induction heating devices. Practical implications The developed magneto-thermal analytical model can be used for fast designing of permanent magnet linear induction heating devices for moving parallelepipedic nonmagnetic workpiece. Originality/value A new analytical coupled model, including the electromagnetic and transient thermal boundary problem with additional algebraic equations and taking into account the nonlinearity, has been developed. The developed model accuracy was validated with a permanent magnet linear induction heating device. Developed coupled analytical model allows fast analysis and designing of such permanent magnet linear induction heating devices.

The aim of this paper is to present the design and modeling of a machine that possesses some advantageous characteristics for wind energy conversion applications. The studied machine is a double stator inner rotor axial airgap flux switching permanent magnet machine (AFSPM). The paper will start by presenting this type of machine and its points of interest. Then, it will continue by introducing the constructed prototype and its specifications and structure. This prototype has been designed based on a reference specification used at GREAH to develop different prototypes and compare their performances. The second part will introduce the reluctance network model specifically constructed for this type of machine. The constructed model was validated by comparing its results to the results from the finite element method model. Finally, the experimental results will be presented and compared to the reluctance network (RN) model results where satisfying agreement between both results was obtained.

This contribution discusses the degrees of freedom that could be advantageously exploited in the conception of permanent magnet (PM) machines in the context of very demanding applications, such as electrical vehicle traction. The aim is to inventory degrees of freedom identified in scientific and technical literatures. Identifying these additional degrees of freedom will help positively respond to highly constrained design problems, which are appearing due to the higher usage of electrical energy in many industrial and consumer products. The goal is also to stimulate new ideas in the design of PM synchronous machines.

The aim of this paper is, first, to extend the application of the hybrid analytical modeling (HAM) approach for the analysis of tubular linear machines (TLPM), something that has never been reported yet in the scientific literature. The HAM consists of a strong coupling between the reluctance network and the Fourier series solution of magnetic scalar potential. In order to assess the merits and capabilities of the HAM, it is applied to the study of the cogging force in linear machines and compared with finite element analyses (FEA). The cogging force is a global quantity, which is very sensitive to magnetic field computation accuracy and constitutes, therefore, a good measure of the accuracy of the HAM as compared with FEA. The HAM should require less computation time as compared with FEA, and is then more suitable for predesign stage. Three different structures are analyzed: a flat linear machine, a TLPM with internal mobile armature, and, finally, a TLPM with external mobile armature. The analyses are conducted, considering the effect of magnetic saturation.

Power capability of synchronous machines, when operating in motoring mode, is discussed in this contribution. Maximum power limits and partial loads operations are both examined in the case of variable speed drives applications when the synchronous motors are driven with idealized inverters with limited volt–ampere ratings. This study is based on a per-unit ${d}$ - ${q}$ model normalized according to the base speed operation quantities. Different control strategies are thoroughly analyzed for different motors parameters. The use of per-unit quantities will help to draw some general conclusions regarding the effect of motors parameters on the drives performance. Since wound field (WF) excited and permanent magnet (PM) excited synchronous motors could be considered as particular cases of hybrid excited synchronous motors, the findings of this contribution would be applicable to all synchronous motors with a magnetic excitation source.

In highly concurrential markets the time to market is reduced, which implies a need of design tools having relatively high accuracy to computation time ratio. It is to address this problematic that the presented modelling approach has been developed. A general framework for the analysis and design of electromagnetic devices is presented. This framework is based on a new hybrid analytical model (HAM) [1]-[4]. The HAM can be applied to different electric machines types (synchronous and asynchronous) and structures (rotating with radial field or axial field, linear flat or tubular structures, or multi-degree-of-freedom structures). It is based on a direct coupling of analytical solution of Maxwell's equations (AM) with reluctance networks (RN). This new technique allows to combine advantages of both methods and should help reduce computation time as compared to finite elements method [3]. This modeling approach is relatively simple and allows the accurate prediction of performances of electromagnetic devices.

In low- to medium-power-rated brushless machines, noise of electromagnetic origin is generally prevailing over mechanical and aerodynamic sources. The appropriate combination of pole and slot of a permanent magnet synchronous motor is one of the keys to its performances among which stands noise reduction. This paper investigates configurations regarding this aspect for distributed overlapping and single-layer concentrated nonoverlapping winding configurations. Chosen combinations are 8 poles 48 slots (8p48s), 8p72s, 46p48s and 50p48s. The air-gap flux density is obtained by 2-D finite element analysis (FEA), allowing to compute the electromagnetic pressure. It then serves as input of mechanical and acoustical 3-D FEA models of the stator with carter.

Fast design procedures of electrical machines require the use of adapted modeling approaches. This is particularly true for axial flux permanent magnet (AFPM) machines, which have an intrinsic 3-D electromagnetic structure. Indeed, accurate modeling of AFPM machines requires the use of 3-D finite-element analysis (3-D FEA), which is highly time consuming, especially at first design stages. This paper presents a new quasi-3-D analytical model (AM) that allows modeling accurately AFPM machines while saving a huge amount of time as compared with 3-D FEA. This new approach combines a multislice AM, which takes into account a part of the 3-D effects, and considers the end-effects by a simple and effective radial dependence modeling of the magnetic field in AFPM machines.

This paper describes an analytical technique for prediction of open circuit eddy-current loss in armature windings and permanent magnets (PM) of series double excitation synchronous machines. First, a 2-D exact analytical solution of open circuit magnetic field distribution in idealized geometry of series double excitation synchronous machine is established. It involves solving Maxwell's equations in stator slots, air gap, PM region, and rotor slots. Then, magnetic vector potential solutions in the stator slots and PM regions are respectively used for prediction of resistance limited eddy currents in armature windings and permanent magnets. This analytical model is then used to estimate eddy-current loss in armature windings and permanent magnets. The validity of the developed model, which is also applicable to conventional designs of permanent-magnet machine, is verified by time-stepped transient finite-element analysis (FEA). The developed model is then used to quantify the effectiveness of segmenting the magnets and armature windings in reducing the eddy-current loss.

This paper presents an analytical model, based on separation of variables solution of Maxwell's equations in low permeabiliy regions (slots, airgap and permanent magnets), allowing the prediction of open circuit and on load magnetic field distributions for flat linear machines with surface mounted permanent magnets. Developed analytical model is validated via comparison to corresponding finite element analyses.

This paper presents an exact 2-D analytical model for predicting the armature reaction magnetic field in idealized structures of permanent-magnet tubular linear machines with surface-inset mounted magnets. The armature reaction magnetic field distributions is analytically derived and compared to finite-element analyses. The analytical solution allows the prediction of the machine inductance and reluctance force in closed forms, and facilitates the evaluation of any possible partial irreversible demagnetization of the magnets. It can also be used to estimate resistance limited eddy-current losses in armature windings and permanent magnets. The developed analytical model can be advantageously used for the analysis and design of a class of linear tubular machines.

We present an exact 2-D analytical model for predicting the magnetic field in idealized structures of surface mounted permanent-magnet tubular linear machines that account for the stator slotting effect. The open-circuit and armature reaction magnetic field distributions are analytically derived and compared to finite-element analyses. The on-load magnetic field calculation is based on the superposition of the component fields due to permanent magnets and armature field reaction. Our model can be advantageously used for the analysis and design of a class of linear tubular machines.

We describe an exact 2-D analytical model for predicting the open circuit magnetic field in idealized structures of wound field and series hybrid excitation permanent-magnet synchronous machines. This technique can be used for either internal or external rotor radial-field machine topologies. It involves analytical solution of Maxwell's equations in stator and rotor slots and annular air-gap/magnet regions. We compare results from this analytical model to corresponding finite-element analyses. We then use it to estimate the cogging torque, induced back-electromotive force, and to study the effects of rotor skewing.

This paper presents an analytical model for prediction of eddy current loss in armature windings of permanent magnet brushless AC machines. The developed model can either be used in the case of internal or external rotor radial-field machines topologies. First, a 2-D exact analytical solution of magnetic field distribution in an actual geometry of slotted surface mounted PM radial flux synchronous machines is established. It involves solution of Maxwell's equations in slots, airgap and PM's region. Then, magnetic vector potential solution in the slots is used for prediction of resistance limited eddy current in armature windings. Finally, results from this analytical model are compared to corresponding finite element analyses.

This paper proposes a classification of three-phase synchronous alternators associated with a diode rectifier and a constant-voltage load. This system is, for example, used in vehicle electric power generation, or in aerogeneration systems. An equivalent circuit model that neglects the different losses and the magnetic saturation is used. The classification is based on the effect of d q inductances, the maximum excitation flux, and the rated current level, on the maximum power limits. A specific normalisation system is used to reduce the number of influent parameters. The classification is done using steady-state equations and confirmed by dynamic simulations and experimental results.

This paper presents an analytical solution for prediction of the armature reaction magnetic field in slotted surface mounted permanent magnet radial flux synchronous machines. This technique is used in the case of internal and external rotor radial-field machines. The magnetic field expressions are developed in both slots regions and magnetic airgap region leading to an exact calculation of the effects of slotting on the airgap magnetic quantities. Results from this analytical model are compared to corresponding finite element analyses. This analytical model is then used to estimate the self and mutual inductances.

In this paper, the suitability of a class of electric machines for vehicle traction applications is discussed. These machines, which are known as hybrid excitation synchronous machines, combine permanent-magnet (PM) excitation with wound field excitation. The goal behind the principle of hybrid excitation is to combine the advantages of PM excited machines and wound field synchronous machines. It is shown that these machines have good flux weakening capability compared with PM machines, and that they constitute an energy-efficient solution for vehicle propulsion.

International audience

This paper presents the analysis of open circuit performance of a permanent magnet linear machine using a new hybrid analytical model (HAM). The goal is to show the capabilities offered by this new modeling approach. The new HAM is based on a strong coupling of magnetic equivalent circuits method and analytical models. The analytical model, based on the formal solution of Maxwell’s equations, is established because of the separation of variables method. The open circuit performance are: 1) cogging force; 2) electromotive force; and 3) open circuit iron loss, obtained from the HAM are compared with corresponding results obtained from a finite-element analysis. A very good agreement has been obtained.

Cogging torque is a source of vibration and noise in PM machines. Its reduction is always sought by electrical machine designers. While its study, in radial-flux PM machines, can often be done using 2-D finite element analysis (FEA), 3-D FEA is always required when it comes to its study in axial-flux PM machines (AFPM). AFPM machines have an inherent 3-D electromagnetic structure. There is a rich literature concerning the study of cogging torque in AFPM machines. Indeed, most of the authors use 3-D FEA for its study. However, 3-D FEA is time consuming and always requires expertise to be done correctly. The goal of this paper is to show that alternative techniques, to study cogging torque in AFPM machines, do exist. It is shown that the analytical approach, used in this paper, can be as efficient as the 3-D FEA while saving a huge amount of time and necessitating less initial expertise.

This paper deals with the computation of vibrations and noise of electromagnetic origin for 'U'-shaped stator core flux switching permanent magnet (FSPM) machines. The investigation concerns a family of FSPM stator/rotor configurations with 12 slots and 10, 11, 13, and 14 rotor poles. More precisely, the study focuses on the influence of different number of rotor poles on the sound power level of U-core FSPM machines. Electromagnetic forces acting on the stator frame inner surface are calculated with the Maxwell stress tensor thanks to 2-D finite element (FE) simulations. The local magnetic force density serves then as a boundary condition to the 3-D finite element vibrational simulations of the whole stator frame with housing. Finally, obtained displacements help the authors to conduct the acoustic computations using a dedicated 3-D FE analysis model. The obtained vibro-acoustic spectra help electric machines designers to make appropriate choice of stator/rotor pole combination with respect to specifications at early stages of the design process.

This paper presents a multi-slice analytical model for prediction of the open-circuit magnetic field in slotted semi-closed permanent-magnet axial flux synchronous machines. The technique is based on 2-D exact solution of the Maxwell's equations using the separation of variables method. The magnetic field expressions are developed in slots regions, slot opening regions, magnetic air gap regions, and permanent magnet regions leading to an exact calculation of the slot effects on the air gap magnetic field. The model is established considering that ferromagnetic parts are infinitely permeable, and end effects at inner and outer radii are neglected. The open circuit machine's global quantities (electromotive force and cogging torque) are then deduced from the local magnetic field expressions. Finally, the accuracy of the presented analytical model is validated by comparing its results to corresponding finite-element analyses for two different axial flux machines.

International audience

Double excitation synchronous machines combine permanent-magnet (PM) excitation with wound field excitation. The goal behind the principle of double excitation is to combine the advantages of PM-excited machines and wound field synchronous machines. These machines can constitute an energy-efficient solution for vehicle propulsion. This paper presents a comparison of the open circuit flux control capability of two structures of double excitation synchronous machines. First, a review of the state of the art of double excitation machines is presented. Then, the structures of these two machines are presented: one is a series double excitation synchronous machine and the other is a parallel double excitation synchronous machine. Finally, the open circuit flux control capabilities of both structures are compared.

National audience; L'objectif de cet article est de rechercher l'existence de paramètres circuits optimaux d'une machine synchrone à aimants permanents qui permettront de remplir des spécifications de type traction électrique ou hybride avec sollicitations sur cycle. Après une présentation succincte de la problématique, les auteurs présenteront le modèle utilisé. Une discussion sur les objectifs d'optimisation sera engagée afin d'en retirer les plus pertinents. Une optimisation multi-objectifs, multi-contraintes utilisant un algorithme génétique sera ensuite mise en œuvre. Elle permettra de déterminer les valeurs des paramètres qui optimiseront les critères choisis tout en respectant les contraintes du cahier des charges.

PurposeThe purpose of this paper is to present an analytical modeling based on lumped parameter magnetic circuits of a hybrid excitation synchronous machine. The model is first established and compared with 3D finite elements analysis and measurements. It is then used to optimise hybrid excitation effectiveness.Design/methodology/approachThe machine studied, which has a 3D structure, requires the use of 3D finite elements method. The 3D FEA tool is still time‐consuming, which limits its use in optimal design process. To overcome this limitation the paper investigates an analytical modeling based on lumped parameter magnetic circuits. The developed model is then used in an optimisation procedure.FindingsThe machine presented has an original structure. It has been subject to a patent protection. The operating principle of this structure has been presented and optimisation of hybrid excitation effectiveness has been investigated. Double excitation allows one to control air gap flux while reducing permanent magnets' demagnetisation risk.Originality/valueThe paper presents an original structure with true field regulation capability. The principle of operation has been presented. A prototype has been built and tested. The paper also presents a 3D finite elements analysis of this machine and an analytical modelling.