Bearingless 300-W PMSM for Bioreactor Mixing

This paper presents a novel exterior rotor topology of a bearingless brushless synchronous motor with rated power of 300 W. Owing to the large possible magnetic gap and the absence of mechanical bearings, this motor is especially qualified for high-purity and low-shear applications (e.g., bioreactor mixing). Both torque and magnetic bearing forces are created inside this disk-shaped motor using a sophisticated control (proportional-integral-differential vector control) with superimposed drive and bearing currents fed to the concentrated combined stator coils. Optimal design is derived based on an electromagnetic analysis using the three-dimensional finite element method (3D-FEM), and the simulation results are verified with a prototype mixer setup.