Bearingless Permanent-Magnet Motor with 4/12 Slot-Pole Ratio for Bioreactor Stirring Applications

This article presents a novel topology for a bearingless permanent-magnet motor. This disk-shaped motor, featuring an exterior rotor, can be advantageously employed in delicate bioreactor processes. Both torque and bearing forces originate inside this magnetically levitated motor and are generated with concentrated combined windings. Using 3-D-FEM analysis, the optimal machine sizing parameters are evaluated with the goal to maximize torque while providing sufficient bearing forces to allow a precise and stable operation. The results from the sizing optimization and from the force and torque analysis have been implemented and tested with a real-size prototype setup.