Heuristic model for YASA axial flux permanent magnet machines design

Thanks to their high-power density, interest in axial flux machines has grown in the last few years. The YASA (Yokeless And Segmented Armature) configuration is a particular structure of axial flux permanent magnet machines in which the manufacturing process of the stator, which was the main issue connected to the axial flux machines, is simplified. The presence of tooth-wound windings increases the cogging torque related to this machine, but its amplitude can be reduced in the design phase. Due to their geometry, a full-3D or quasi-3D finite element model is necessary to simulate the behavior of axial flux machines, and the YASA configuration is not an exception. The analysis of such models is time-consuming, and many iterations are required to design the electrical machine. A preliminary heuristic model was developed to reduce the time needed for the design process. Starting from several design constraints and iteratively determining some parameters, the model derives the remaining dimensions, the airgap magnetic flux density produced by the permanent magnets, the consequent value of the ampere-turns needed to develop the requested torque, and the phase-induced voltages. At the end of each iteration, the obtained values are checked to be in the constraints. If a condition is not satisfied, the process restarts, changing the appropriate parameters. The output of this model is the input of a finite element analysis to reduce the number of iterations needed to find the optimal design of the device. The model was implemented in a MATLAB GUI and used to design a YASA machine. The output of the heuristic model was validated through finite element simulations, verifying that the design constraints are respected.