An analytical method to determine the no-load and armature reaction magnetic fields of a single-sided, axial flux permanent-magnet synchronous generator without armature core is presented. Laplace's equation is solved in the rectangular coordinate system to give the scalar magnetic potentials, using a Fourier series method. For computation of the armature reaction field, a multi-current-sheet model is employed in order to account for the distributed nature of armature conductors in the axial direction. Finite element analysis and experimental results on a prototype machine are presented for verifying the accuracy of the proposed method.