Analysis of axial field magnetic gears with Halbach arrays

Magnetic gears can scale the torque and speed of rotary systems, while avoiding problems associated with transferring torque through physical contact. This work uses 3D finite element analysis to parametrically characterize the performance benefits which can be obtained from applying Halbach magnet arrays to axial field magnetic gears. It is found that Halbach arrays decrease the flux density in the adjacent back iron, allowing the thickness of these yokes to be reduced. Also, using Halbach arrays increases the magnitude of the desired magnetic flux spatial frequencies in the air gaps, increasing torque, and decreases the magnitude of undesired spatial frequencies, decreasing torque ripple. Additionally, the use of Halbach arrays on both rotors increased the torque volumetric torque density for two different design points by 43.6% and 65.7% to 183.9 and 155.8 kN*m/m³, respectively, and decreased the cogging torque on both rotors.