Analysis and performance of an ironless stator axial flux PM machine

This paper presents the analysis, design and performance of an axial flux permanent magnet (AFPM) machine with an ironless stator. The topology has a large airgap length and zero core losses. A machine model that uses both lumped magnetic circuit and finite element method results is used with a multi-variable optimization algorithm to obtain the optimum machine dimensions. Special attention is given to the magnet interpolar gap to ensure a certain minimum plateau width for brushless DC operation. The large airgap length allows several approximations to be made that simplifies the machine model. A prototype machine is constructed and evaluated. Measured results of the armature reaction effect in the large airgap are given and discussed.