Analytical design of an axial flux permanent magnet in-wheel synchronous motor for electric vehicle

This paper deals with the analytical design of an axial flux permanent magnet (AFPM) in-wheel synchronous motor for electric vehicles (EVs). AFPM motor is a pancake-type high torque density motor that fits perfectly the wheel of an automobile vehicle and that can, thus, be easily and compactly integrated into the wheel. Therefore, AFPM motor seems to be a better choice than radial flux permanent magnet (RFPM) motor for this kind of application. First, a design program of AFPM synchronous motors developed by the authors in Matlab environment is presented and validated by experimental results. This program is very simple to use and useful during the first stage of the design of a new motor in order to evaluate its performances and overall dimensions with reasonable accuracy (although more sophisticated methods, such as Finite Element Analysis (FEA), are required in more advanced phases of the design). In a second time, this program is used to design one of the four in-wheel motors of an urban EV. The results confirm that AFPM motor is a competitive choice for this application. Indeed, it meets all the requirements of the EV and fits perfectly the shape and size of a classical rim of an automobile vehicle wheel. Moreover, the results are compared with those obtained for a more conventional RFPM motor. This comparison shows that AFPM motor is a better choice than RFPM motor for in-wheel motor applications.