Magnetic gears are non-contact means of torque transmission which utilize the interaction of magnetic fields in place of the meshing teeth of mechanical gears to achieve a change in rotational speed and scale up/down the torque. A subscale magnetic gearbox featured a radial flux focusing arrangement consisting of three main rotors in the active region called inner, cage and outer rotors. In this arrangement, ferromagnetic cage rotor poles modulate flux between the inner rotor and outer rotor permanent magnets to achieve the gear reduction. Replacing the solid metal bars with laminated stacks for the cage modulating pieces as well as retaining pieces of the inner and outer rotor magnets reduces eddy current losses in the axial direction, a main source of losses in magnetic gears, while preserving the magnetic flux directed in the radial direction. Both of these features are key for overall system performance.
Given the potential of demagnetization of the permanent magnets and damage to the components at high temperature, multiphysics thermal analysis is conducted on a subscale flux focusing magnetic gearbox to predict temperature distribution and thermal stresses. A conjugate heat transfer (CHT) method is used in a 3D academic code, FLUENT, to predict heat flux and the coupled non-adiabatic external flow field and temperature field on the inner, cage and outer rotor with a Finite Volume Method (FVM). Thermo-elastic behavior of the laminated components are assigned through anisotropic materialistic characters in a finite element method (FEM), where the thermal and centrifugal stresses are calculated.