Rotor losses in laminated magnets and an anisotropic carbon fiber sleeve

High speed fault tolerant permanent magnet machines have strong asynchronous airgap harmonics, making them susceptible to rotor eddy-current losses. These losses can be reduced by using novel high resistivity materials like plastic bonded magnets and carbon fiber reinforced retaining sleeves. This paper examines by numerical studies the consequences for the losses of using these materials. The effect of laminating the magnets and the losses in the anisotropic sleeve are analysed with 3D simulations, using simplifications determined with 2D simulations. The anisotropic resistivity of the sleeve roughly doubles the losses compared to an isotropic sleeve, while laminating the magnets in n slices reduces the losses by 1/n^1.8.