Winding Factors and Harmonics of Coreless Axial Flux PM Machines

This paper provides a comprehensive analysis of the winding factor and winding harmonic distribution in coreless stator axial flux permanent magnet (AFPM) machines. The topology of this type of machine and its similarities to conventional cored AFPM machines are discussed. Popular pole/coil number combinations in coreless stator AFPM machines are identified and analyzed in detail. It is demonstrated that the winding factor in these machines varies with radius and can be expressed as the product of the conductor distribution factor, pitch factor, and coil group factor. The formulas for each factor are derived and presented in multiple forms based on different parameters. The winding factors for the considered pole/coil combinations are calculated under different conditions, and their corresponding harmonic distributions are compared. The results indicate that certain pole/coil combinations yield higher winding factors, improving torque capability.