Design of an axial-flux permanent magnet machine for a solar-powered electric vehicle

This paper concerns the design optimization of two axial-flux permanent magnet (AFPM) machines, aimed to be used as a direct drive in-wheel motor for the propulsion of a solar-powered electric vehicle. The internal stator twin external rotor AFPM machine topology having either a distributed or toroidal stator winding configuration is investigated. The objective of the design optimization is to minimize the total volume of the machine. A gradient-based optimization algorithm is employed on a non-linear 2D equivalent motor model. The motor model consists of coupled electromagnetic and thermal models based on an Isogeometric Analysis (IGA) approach. A wide range of pole-pair numbers are optimized and compared in terms of power density and efficiency. Finally, the radius to evaluate the 2D model as a function of the pole-pair number is given, which minimizes the discrepancy with respect to the 3D finite element method (FEM).