Analytical Model of Magnetic Force for Axial Stack Permanent-Magnet Bearings

Based on magnetic field of plane point magnetic charge, virtual work principle, and superposition theorem, the magnetic force analytical model for axial stack permanent-magnet bearings (PMB) is established. The aim is to solve the problem of the magnetic force analytical model´s lack of being convenient in engineering design calculation of axial stack PMB. The relationship between magnetic force and structure parameters of PMB is analyzed. ANSYS simulation is adopted to test the validity of the magnetic force analytical model. The results indicate that the magnetic force of axial stack PMB is proportional to the magnetic annular average perimeter and the square of residual magnetism induction density, and that the magnetic force increases with an increment in the magnetic annular radial width and magnetic annular number. In the case of similar geometric parameters, the magnetic force of the same direction magnetization axial stack PMB is minimum: when the number of stack magnetic ring is 4, the maximum magnetic force of reversal magnetization axial stack PMB is approximately 4 times as much as the maximum magnetic force of equi-directional magnetization axial stack PMB; when the axial offset is only half of the axial length of single magnetic ring, the axial magnetic force is the maximum. Accordingly, the maximum magnetic force of rotational magnetization axial stack PMB is roughly 1.5 times as much as the maximum magnetic force of reversal magnetization axial stack PMB. When the axial deflection is equal to the axial length of single magnetic ring, the axial magnetic force is the maximum.