Comparison of Slotted and Slotless High-Speed Permanent Magnet Motors with Toroidal Windings

This paper compares the electromagnetic and mechanical performances of 2-pole slotted and slotless high-speed permanent magnet (HSPM) motors with toroidal windings. Both HSPM motors are optimized for maximum torque by the finite element method (FEM). It is found that the slotless motor with 6 coils has advantages of low stator iron loss and rotor eddy current loss due to no slotting effect, but has significantly high AC copper loss. Although both HSPM motors with toroidal windings have the same winding factor, the slotted motor with 6 slots has higher torque, higher PM utilization, lower AC copper loss, and larger winding inductance. Finally, the mechanical stress analyses show that the rotor designs of two motors are safe for high-speed operation.