Analytical Model for Design of High-Speed Slotless Brushless Machines with SMC Stators

This paper presents a general analytical model for the design of high-speed slotless permanent magnet brushless motors equipped with surface-mounted magnets and using soft magnetic composite material (SMC) in the stator. The electromagnetic model is formulated in polar coordinates and based on the prediction of the two-dimensional magnetic field distribution in the magnets/air-gap/windings/stator core regions, produced by the magnets and the stator currents windings. It takes into account the effects of the stator core eddy currents induced in the massive homogeneous SMC material. Different machine performances like the instantaneous torque under brushless operation and the total magnetic losses are evaluated. The analytical design model is validated by FE analysis in terms of magnetic field distribution and total stator core loss. The influence of the stator yoke thickness and the SMC material conductivity on the motor performances is investigated. Experimental results are given for the stator magnetic losses.