Design, modelling and prototyping of an electrodynamic self-bearing axial-flux permanent magnet motor

Two topics have been the subject of numerous researches in the field of rotating machineries those past years. On the one hand, electrodynamic magnetic bearings (EDBs) ensure a contactless guidance of the rotor relying on the interaction between the permanent magnets (PMs) magnetic fields and the currents they induce in the conducting parts of the bearing structure. On the other hand, axial-flux permanent magnet (AFPM) machines allow to drive a PMs rotor disk by injecting three-phased currents in the windings. Topologies of electrodynamic thrust bearings (EDTBs) and AFPM machines present a significant number of similarities. Starting from this observation, this Master's thesis introduces a new machine topology combining both a bearing and motor behavior to obtain a self-bearing AFPM machine in a single winding. First, a model describing the axial and rotational dynamics of such a machine is developed. This model directly relates the axial displacement to the force developed by the EDTB and the rotational motion to the driving torque generated by the AFPM machine and the drag torque arising from the EDTB. The obtained model is constituted of eight non-linear first-order differential equations with a set of twelve parameters. The calculations required to determine those parameters using static FEM simulations are also detailed. Furthermore, this model can be used to obtain several results regarding the quasi-static and dynamic behavior of the self-bearing AFPM machine. Based on the linearization of the obtained model, this work assesses the stability properties of the system under constant rotational speed, based on a root locus analysis. The evolution of the quasi-static equilibrium points as a function of the spin speed is also discussed for a fixed axial displacement or a given external force applied to the rotor. Moreover, this model allows to simultaneously obtain the axial and rotational dynamic behavior of the self-bearing AFPM machine in various situations, e.g. at start-up and when subjected to external force perturbations or variations of the reference spin speed. A last use of the model is to determine optimal dimensions and parameters for the machine, based on a set of criteria describing the EDTB and AFPM motor performance. In this work, this purpose is achieved through a parametric analysis, but this model can be used to conduct a conventional optimization on the machine parameters. Finally, the prototype of a self-bearing AFPM motor and the associated testbench are developed as a proof-of-concept. The functioning of the EDTB and AFPM motor alone has been partially validated based on experimental measurements, but the fact that the prototype is not completely functional has kept us from determining the performance of the complete system. However, critical issues in the development of such a machine have been highlighted and solutions to avoid and solve them have been proposed. This Master's thesis thus paves the way for further works combining a fully passive magnetic guidance and a motor behavior within the same device.