Infoscience

Thesis

Modélisation analytique multiphysique pour la conception optimale de moteurs synchrones à aimants permanents

During the last years, permanent magnets synchronous motors have become a reference in the industrial world, both from the economical and the technical point of view, because of their very good performance in both regards. Thus, application of specific methodologies and algorithms during the design phase has become a must. In this thesis, the analytical modelling of permanent magnet synchronous motors for stator configurations with and without teeth is presented. Several physical aspects, such as magnetic, thermal and electrical phenomena, are taken into account. For the magnetic part, several models are presented which all have their own areas of application. Some of them take the magnetic saturation of the ferromagnetic parts into consideration. The simplified thermal model is based on an equivalent Kirchhoff circuit in which convection and radiation are included. Concerning the determination of the electrical characteristics of slotless machine configurations, the determination of the back-emf and of the inductances using the method of images are presented. Special emphasis has been placed that the tendencies of the variations of the modelled phenomena as they are observed with changes in other parameters or criteria are correctly represented. This is almost more significant that the accuracy of the model itself. The models are validated and improved by using finite element simulations. The mathematical expressions of the design problems are taken into account to allow the mathematical optimisation applied to converge towards the optimal solution without failure. Thereby, the objective is to avoid non-continuity of the functions and their first derivatives and to reduce the space where the functions are not mathematically defined. In the "Solar Impulse" project, which aims to realise an around-the-world flight with an airplane using only the solar radiation as energy source, a prototype is optimised and built. A prototype motor has been built and experimentally analysed, to be able to further validate and improve the analytical model used for the optimisation of the machine. The originalities of this thesis can be summarised as follows : modelling of the magnetic phenomena, with several specific models adapted for different configurations ; formulations of the physical phenomena adapted for the design phase ; comparison between analytical and finite element simulations in order to validate or/and improve the analytical models ; use of the method of images to determine the inductances in a slotless motor ; design optimisation by taking into account several physical phenomena where the free parameters are analysed globally ; design and manufacturing of a prototype for a concrete project which allows to completely validate the results of the optimisation and the analytical models.

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