Low-Cost and Compact Disposable Extracorporeal Centrifugal Blood Pump Utilizing a Homopolar Bearingless Switched Reluctance Slice Motor

The high biocompatibility and high durability of disposable extracorporeal centrifugal blood pumps (CBPs) utilizing magnetic bearing or bearingless motor technology make them perfect for supporting cardiopulmonary circulation for patients. However, the rotor incorporated in the disposable unit typically uses high-cost and environmentally-unfriendly rare-earth permanent magnets (PMs), leading to economic and environmental issues. This paper proposes a centrifugal blood pump with a PM-free impeller/rotor in the disposable pump head utilizing a 12/8 bearingless switched reluctance slice motor (BELSRM). Two axial-magnetized PM rings and two iron rings are mounted symmetrically above and below the tips of the stator poles. The biased magnetic flux generated by the PM rings forms a closed vertical magnetic circuit (homopolar flux circuit) with a PM-free rotor, providing high passive stiffness and large positioning forces independent of the rotor angle. A three-dimensional (3D) finite element analysis (FEA) model was used to evaluate the rotor support stiffness, the current-force coefficient, and the rotational torque. A prototype bearingless slice motor (BELSM) and a disposable pump head with a diameter of 50 mm PM-free impeller/rotor were fabricated. The radial magnetic levitation and the rotation were actively controlled by displacement and speed feedback control systems, respectively. A mock circulatory loop filled with 40wt% aqueous glycerol solution was set to evaluate the performance of the proposed CBP. The CBP provided a maximum flow rate of 4.59 L/min and a maximum head pressure of 214.5 mmHg at 2300 rpm and 2400 rpm, respectively.