Magnetic Field Analysis and Calculation of Slotless Axial Flux Permanent Magnet Motor with Sinusoidal Back EMF

For slotless axial flux permanent magnet motor (AFPM), the 3-D finite element method is the most accurate design approach, but it suffers from long computational time. To address this issue, this paper proposes an analytical design method for slotless AFPM with sinusoidal back EMF. Initially, the open-circuit electromotive force (EMF) of AFPM with toroidal and bunched winding is derived using the winding function method. Subsequently, a 3-D analytical model for the magnetic field of AFPM with sinusoidal back EMF is established, with a detailed analysis of the air-gap density. Finally, the effectiveness of the proposed method is validated by comparing the results with those obtained from finite element methods.