Conventional bearings require lubrication and regular maintenance, making them unsuitable for liquid environments. To expand the applicability of bearingless motors in ventricular assist device (VAD) pumps, this study proposes a passive, zero-power magnetic bearing using PMs repulsion for shaft support. Radial stabilization is achieved by arranging same-pole PMs on the stator and rotor; axial support uses stator PMs positioned between two rows of rotor PMs. To minimize blood-flow disturbance, the stator-rotor gap was increased to 5mm, and rotor PMs were overlapped by 1mm with the stator extension to enhance repulsive force. Three-dimensional finite-element method (3DFEM) under various operating conditions characterized bearing performance. Results show rotational speed doesn't affect bearing stiffness. Eccentric rotation around the rotor's axis generated a restoring force, and torsional loading in the radial direction confirmed system rigidity. However, instability was observed in the axial (thrust) direction. To address this, a correction mechanism combining a stator electromagnet and rotor electromagnetic steel was analyzed. Theoretical predictions matched 3DFEM results for radial force but deviated in axial. These findings suggest the need to integrate an active thrust-control structure into the motor. Future work will improve axial force correction methods and experimentally validate the proposed design.
Yatsu et al. (Sun,) studied this question.