Novel bearingless brushless motor in exterior rotor construction for stirred bioreactors

The paper presents a novel topology for a bearingless permanent magnet motor which is especially qualified for high-torque and yet gentle bioreactor stirring. Both torque and bearing forces are created inside this magnetically levitated disk-shaped motor using a sophisticated control with superimposed coil currents. An optimal design is derived using 3D-FEM analysis and the results are verified with a prototype setup.