Design and Analysis of Axial-Flux Permanent Magnet Synchronous Machines as Traction Drives for Electric Vehicles

This paper investigates axial-flux permanent magnet synchronous machines as traction motors for use in electric vehicles. The assumed boundary conditions facilitate their application as near-wheel motor. The aim is to combine the advantages of a central motor with the advantages of a wheel hub motor. All of the investigated motor variants are realized with double stators, i.e. the both sides of the rotor disc are each faced by a stator. The advantages of this arrangement are explained in detail, compared to double-rotor variants or variants with one stator and one rotor. In addition, it is analyzed whether the use of sector stators is feasible, and if so, which are the technical challenges to cope with. Moreover, the advantages and disadvantages of axial-flux permanent magnet machines (AFPM) compared to conventional radial-flux machines are summarized. Finally, different types of windings are investigated in consideration of the torque curve. The end winding's shape is an additional element to consider in the design process.