A Comparative Study of Stator Winding Technologies for Coreless Axial Flux Permanent Magnet Machines

Recently, axial flux permanent magnet machines with coreless windings have been proposed for many applications, from low-speed servo systems to high-speed electric propulsion. These machines have zero cogging torque and core losses, a highly linear behaviour, and remarkable overload capabilities. Conversely, thermal behaviour, efficiency, torque density and power density strongly depend on the specific stator winding technology. This paper reviews stator winding technologies for coreless axial flux permanent magnet (AFPM) machines, focusing on their potential benefits and limitations. Additional contributions include the analysis and comparison of different winding solutions for low-speed and high-speed machines. The presented results can be used as guidelines for the selection of the most appropriate winding technology for a number of practical applications.