This work is an investigation into the curvature related potential for flux to flow in the radial direction in the back-iron of laminated axial flux machine cores. Analytical and numerical models are presented. Analysis based on these models has shown that, in practical axial flux machines, the radial component of the flux density can be neglected with respect to the flux density distribution in the core back-iron. It has also been found that if the core permeability, core conductivity and number of poles are sufficiently high then power loss due to curvature related cross-lamination flux is negligible compared to normal eddy current losses. A closed form expression to predict losses due to curvature related radial flux is also presented. This expression allows axial flux machine designers to make quick assessment of the need to consider these losses when designing axial flux machines.

This thesis aims to design a motor with axial magnetic flux, which could be used as a direct propeller of heart replacement pump. It is divided into several parts, first of which deals with describing possible axial motors construction design. Next follows up the description of possible motor designs, from which the non-ferrous one was chosen. After that, an analytic calculation of motor’s properties is conducted. Calculated parameters are thereafter verified by software tools using finite element method. Finally, the whole motor was manufactured and had its parameters tested and verified.

This thesis develops design methodologies for megawatt(MW)-scale yokeless and segmented armature (YASA) generators for wind turbine applications. The methodologies include the electromagnetic, the structural and the thermal designs of a YASA generator. The design process starts with developing an analytical method to generate preliminary machine designs for a megawatt-scale YASA generator. This analytical approach considers both electromagnetic and structural aspects of a generator, the parameters of which were obtained and visualised on a design reference map. This new concept of displaying machine parameters is useful for a designer to identify the relationship between them. An optimisation tool using pseudo-weight approach is integrated into the analytical tool to determine a optimum machine design. This is a flexible optimisation tool, allowing the user to give priorities to each objective function. The analytical calculation has reduced the design space for suitable machine candidates to be applied in further finite element analysis (FEM). In finite element analysis of an optimised YASA machine, the electromagnetic performance of a 1 MW YASA generator was produced and verified with analytical and experiment results. This is followed by structural optimisation with finite element method, where a spider wheel with a support ring geometry is applied to the rotor plate. This reduces the structural weight by more than 50% while the structure retain strong stiffness. Finally, the cooling system of the stator of the YASA generator is studied and the cooling channels design is proposed. Simulation results show that the stator of a 1 MW YASA generator can be effectively cooled with forced air.

Dans le cadre du développement du véhicule électrique hybride, les machines électriques pour la traction sont l’objet d’un effort toujours plus important de recherche et de développement. En particulier, les contraintes d’encombrement allouées à ces machines sont toujours plus sévères et la recherche se porte vers des structures de machines compactes. C’est dans ce contexte que nos travaux se sont portés sur l’étude et le dimensionnement de machine à flux axial pour une application hybridation douce (Mild Hybrid) d’alterno-démarreur monté sur vilebrequin de puissance 50 kW et de couple 205 Nm en régime transitoire. Un état de l’art des machines à flux axial est présenté. Une analyse des configurations de bobinage avec la méthode de l’étoile des encoches est détaillée. Un début d’analyse de la machine à commutation de flux est proposé. La méthodologie de dimensionnement est étayée. Elle repose sur des études de sensibilité, un dimensionnement paramétrique, mais aussi une optimisation de la machine. Les modèles utilisés sont de type éléments finis et surface de réponse par plan d’expériences. Enfin, une étude thermique de la machine est effectuée et des pistes sont données pour l’amélioration de l’échange thermique par refroidissement diphasique. / In the context of development of the hybrid electric vehicle, electric machines for traction are under extensive investigation. In particular, volume constraints are more and more severe and research is carried out towards compact structures. This work is focused on the study and the design of axial flux machine for a mild-hybrid application of an integrated starter generator mounted on the crankshaft. Its ratings in transient mode are 50 kW and 205 Nm. A literature review of axial flux machines is presented. A analysis of winding configurations with star of slots method is detailed. A beginning of analysis of switching-flux machine is proposed. The methodology of design is detailed. It is based on sensitivity analysis, parametric design and optimization of the machine. Utilized models are finite element model and response surface by design of experiments. Finally, a thermal study of the machine is carried out and some ideas are given to improve the thermal exchange by diphase cooling.

The aim of this doctoral thesis is to design a motor-generator for swirl turbine. Swirl turbine is a relatively new type of turbine developed at the Department of Fluid Engineering Viktor Kaplan Energy Institute FME BUT. Swirl turbine is designed for use on small head, where the classical types of turbines either poor efficacy or are economically disadvantaged. As suitable construction for the motor-generator was selected synchronous machine with permanent magnets and with axial magnetic flow with coreless stator. As part of the work is carried out calculating the properties of turbines for defined operating point simulation model of the turbine. After already made draft motor-generator to optimally meet the characteristics of the turbine. The complete design of the motor-generator is validated by calculating the finite element method models. Designed machine must be able to work as a generator and as a motor, if it was necessary to use a turbine as a pump.

Le travail présenté dans ce mémoire traite de la problématique du dimensionnement de structures innovantes de génératrices, à savoir les machines à flux axial ou encore discoïdes, destinées aux éoliennes de grande puissance allant jusqu'à deux dizaines de mégawatts. Les machines synchrones à aimants permanents à flux axial étant intrinsèquement tridimensionnelles, l'optimisation de leur dimensionnement nécessite un modèle dimensionnant tridimensionnel et multiphysique qui peut être, de par sa nature 3D, très consommateur en mémoire et en temps de calcul. On se propose donc, dans ce mémoire, de développer une approche de modélisation par constantes localisées offrant un très bon rapport entre vitesse de calcul et précision afin d'accélérer de façon significative les premières phases de la procédure de dimensionnement. L'approche par constantes localisées peut par ailleurs s'appliquer de manière similaire aux principales physiques concernées (magnétique, thermique et mécanique). Plus particulièrement pour la partie magnétique, l'approche par constantes localisées est mise en œuvre par le biais de réseaux réluctants magnétiques génériques. Le principe de la méthode développée repose sur le découpage de la géométrie de la machine en volumes élémentaires finis parallélépipédiques à l'instar de qui est fait avec la méthode des éléments finis. En effet, chaque volume élémentaire étant modélisé par un réseau réluctant local, le découpage de la géométrie conduit à la génération automatique du système algébrique magnétique de la structure et dont la solution fournit la distribution locale du potentiel scalaire magnétique aux nœuds des volumes élémentaires. Cette approche de modélisation a été implémentée dans un code de calcul interne au GREAH. La modélisation de la génératrice à flux axial par réseaux réluctants a été validée par des simulations 2D et 3D par éléments finis. Le code de calcul développé intègrera les travaux en cours sur les modèles thermique et mécanique au GREAH afin d'aboutir à un code de calcul multi-physique par constantes localisées / The aim of this PhD thesis is to propose a design approach of the axial flux permanent magnet synchronous generator for multi megawatts wind converter application. The axial flux permanent magnet synchronous machine being intrinsically three dimensional, a 3D multiphysics sizing model is needed in order to conduct an efficient optimal design of this type of machines. Unfortunately, 3D multiphysic models are generally issued from finite element method. So, they are very heavy to be handled in a reduced time from an engineer point of view and especially at the first stages of the design procedure. In order to address the faster axial flux machine design, this PhD thesis develops a lumped parameters approach modelling offering a good computation time to precision ratio and thus helping to reduce considerably the spent time in the first stages design procedure. The lumped parameters modelling approach is also well suited for the modelling of the three main physics to be considered in an electrical generator (magnetic model, thermal model and mechanical model). For the magnetic model, the lumped parameters approach consists, in this thesis, in the development of a generic magnetic reluctance network linked to the machine geometry. In fact, the latter is divided into parallelepipedic elementary volumes, each of them is modelled by a local reluctance network. The reluctance network of the hole machine geometry results then automatically in an algebraic magnetic system, the solution of which provides the distribution of the scalar magnetic potential at the elementary volume nodes. The described lumped parameters modelling was implemented in a computational code developed at the GREAH Lab. The effectiveness of the reluctance network axial flux machine modelling was validated by 2D and 3D finite element simulations. The lumped parameters computational code will regroup the ongoing developments of thermal and mechanical models at the GREAH Lab in order to reach the completion of a mutliphysics lumped parameters computational code.

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