Design Considerations for Spindle SPM Motors With Minimized Usage of Rare-Earth Magnets

This paper describes a technique to minimize the use of rare-earth magnets in surface mounted permanent magnet (SPM) motors, while still meeting the specifications of the motor. The method is based on calculating the no-load flux linkage in the stator winding in terms of a volume integral applied to the volume of the PM inside the machine. We apply it to three SPM motors equipped with integral-slot windings. Both finite element analysis and experimental results show that this technique can not only improve the machine performance but also reduce the use of magnets while still maintaining the required value of average torque.