Experimental study on reducing cogging torque and core power loss in axial-flux permanent-magnet machines with slotted winding

The axial flux permanent magnet machine (AFPM) topology is suited for direct-drive applications, and due to their enhanced flux weakening capability AFPMs having slotted winding are the most promising candidate for use in wheel-motor drives. In consideration of that, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having a slotted winding in order to achieve substantial reduction of cogging torque and power loss in the stator core. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve off-line modifications of the overall magnetic arrangement at the machine air gaps, such as magnet skewing, angular shifting between rotor discs and accommodation of either PVC or Somaloy wedges for closing the slot openings. The paper discusses experimental results and gives guidelines for the design of AFPMs with improved performance.