Improved Analytical Model for Predicting the Magnetic Field Distribution in High-Speed Slotless Permanent-Magnet Machines

This paper presents a general analytical 2-D model for computing the magnetic field distribution in high-speed slotless surface-mounted permanent-magnet machines. This model is suitable for machines equipped with soft magnetic composite or laminated steel stators and with retaining sleeves that can be conductive or non-conductive and magnetic or non-magnetic. The analytical model considers the contribution of magnetic fields produced by the rotor magnets, stator windings currents, and eddy currents induced in the conductive regions in the stator and rotor. The computation accounts for the relative recoil permeabilities of the magnets, retaining sleeve, and stator core material. The analytical model is validated by 2-D finite element analysis and used to compute and analyze the electromagnetic torque components due to the different magnetic field sources interactions.