Bearingless Slice Motors with PM-free Rotor for Disposable Centrifugal Blood Pumps

The principle, prototyping, and performance evaluation of two novel bearingless slice motors (BELSMs) designed for disposable centrifugal blood pumps are presented. Both BELSMs do not use permanent magnets in the rotor of the pump housing, thus reducing the cost of disposable components. One BELSM has twelve shared coils for rotation and magnetic levitation. The BELMS achieves passive stiffness in the axial and tilting directions using magnetic coupling generated in the axial direction. The stator structure is relatively simple but requires twelve amplifiers to drive the coils independently. The other BELSM has three-phase coils for rotation, two-phase coils for magnetic levitation, and magnetic couplings formed radially. The three-phase amplifier can drive the motor coils, and the two single-phase amplifiers can drive the suspension coils, simplifying the power circuit, but the stator structure is complex. A centrifugal pump was realized using the former BELSM. The maximum flow rate was 4.3 L/min, which was insufficient for the 5 L/min required for a blood pump. Due to the coil's large inductance and the amplifier performance limitation, it could not reach sufficient rotation. In the second BELSM, the pump's maximum torque and maximum speed have obtained the values required to achieve the target flow and pressure of the blood pump.