Sensitivity analysis of YASA axial flux permanent magnet machines

This paper reports the sensitivity analysis of a Yokeless And Segmented Armature (YASA) axial flux permanent magnet machine. The structure of the device facilitates its stator construction and assembly but leads to some design aspects that can affect the device's performance. The sensitivity of a YASA machine to these aspects is investigated, analyzing the results derived from Finite Element (FE) simulations of a full-3D model of the device. Several simulations are performed, changing the shape of stator teeth, the airgap length and the rotor material. For each value of these parameters, the Root Mean Square (RMS) value of the phase-induced voltage for different rotational speeds is derived from simulation results, and the electric constant is calculated to evaluate the impact of each factor. Results highlight that comparing the behavior of stair-like and continuous trapezoidal cross-sectioned stator teeth, the electric constant decreases of a factor, which depends on the number of steps of the discrete section passing from a trapezoidal to a stair-like cross-section. Moreover, the slope of the Electro Motive Force (EMF) with respect to the rotational speed decreases linearly with the airgap length, and it is strongly affected by the relative permeability of the rotor material. If it is non-magnetic, the electric constant is much smaller than in the case of ferromagnetic rotor material.