This paper presents a study on the magnitude of axial force in axial machines with functionally graded permanent magnets (FGPMs). Axial load exerted on facing bodies is calculated using Maxwell stress tensor and moving charges. The functionally graded properties of FGPM are presumed to decrease the axial force for the small values of air gaps between the rotor and the stator. This hypothesis is tested against various grading patterns of FGPM as well as various air gap sizes. The results show that replacing conventional permanent magnets by FGPMs in axial devices can significantly affect on axial load. Therefore, an appropriate graded pattern can be devised for each particular application in order to optimize the drag force. It can simultaneously maximize the generated torque while minimizing the destructive axial load.

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