Extracorporeal Blood Pump driven by a Novel Bearingless Split-Tooth Flux-Reversal Motor

This paper describes a novel bearingless split tooth flux reversal motor with integrated centrifugal blood pump. This motor has a magnet-free rotor, and is capable of operating at up to 3000 rpm with up to 100 mNm torque. The motor also has 50 N radial force capability for centering the rotor. The motor rotor is 50 mm diameter, housed in a 170mm wide stator. The motor has a novel magnetic configuration wherein the force generation is independent of the rotor angle. This allows simple radial force generation using stator-fixed currents. The motor torque is generated using commutated two-phase currents. Finite element simulations are used to optimize the design in order to achieve sufficient radial force and motor torque, while minimizing cogging torque. The design also achieves an axial passive magnetic stiffness of 5.4 N/mm, which is the constraint on axial motions of the rotor. This paper includes mechanical design and fabrication details, as well as experimental closed loop levitation and speed control performance. With an integrated impeller, the rotor and the centrifugal pump are tested by pumping fluid in a closed circuit to obtain experimental pressure-flow curves with impeller-limited performance.