Electromagnetic Design Algorithm for Axial Flux Permanent Magnet Machines

The interest in axial flux machines has grown in recent years because of their high power density. Considering their geometry, 3D or quasi-3D Finite Element (FE) models are necessary to simulate their behavior: the analysis of such models is time-consuming, and the iterations needed to derive the final design may require long computation times. This paper describes a fast design procedure for axial flux Permanent Magnet (PM) machines based on simple closed expressions relating the main electromagnetic quantities to geometric parameters. Starting from the commonly used design constraints, the model derives, in about 0.4 s, the airgap magnetic flux density produced by the PMs, the value of the ampere-turns needed to develop the requested torque, the main geometric machine dimensions (i.e., rotor yoke, teeth geometry, PMs shape), and the efficiency. FE simulations of the obtained configuration have been performed to verify the effectiveness of the analytical model, assessing that the initial specifications are respected. Furthermore, a prototype was built and tested. The measured values of the no-load airgap magnetic flux density, induced voltages, developed torque, and efficiency were compared to the ones estimated by the proposed model, highlighting the good consistency between the analytical, FE, and experimental results.