Development of a small magnetic levitated centrifugal blood pump using a radial type self-bearing motor and axial position change of rotor-impeller by rotational magnetic field

A small magnetic levitated centrifugal blood pump using a radial type self-bearing motor has been developed for use as an implantable artificial heart. In order to realize an implantable blood pump for a small adult patient, miniaturization and high efficiency of the device are necessary. In this study, a radial type self-bearing motor which is small-diameter and thin was developed, and the axial position change of the rotor-impeller by the rotational magnetic field was proposed. Magnetic suspension characteristics and motor performance were compared the center axial position of the rotor with the displaced axial position of the rotor. Additionally, a magnetic levitated centrifugal blood pump using the self-bearing motor was developed, and pump performance and levitation performance were measured. The magnetic suspension performance in the radial direction was enough ability to control the radial position of the rotor. The magnetic suspension force in the radial direction decreased by displacing the axial position of the rotor. The passive stability performance in the axial direction was enough ability to suspend the rotor. The restoring force was possible to be varied by the rotation magnetic field. The motor performance decreased by shifting the phase angle of the rotational magnetic field from 90 degrees and displacing the axial position of the rotor. At the operating condition with a flow rate of 5 L/min against a pressure of 100 mm Hg, the oscillation amplitude in x, y, z direction were 0.014 mm, 0.014 mm and 0.039 mm, respectively. And, the total power consumption was 7.1 W. The developed magnetic levitated centrifugal blood pump has demonstrated sufficient levitation performance and low total power consumption. The average displacement in z direction of the rotor-impeller was possible to change by changing the phase angle of the rotational magnetic field. By decreasing the phase angle from 90 degrees in range of from 60 degrees to 90 degrees, it is possible to improve the levitation performance with just a little increases the total power consumption