Magnetic Field and Specific Axial Load Capacity of Hybrid Magnetic Bearing

Permanent magnet bias hybrid magnetic bearing (HMB) which combines active and passive actuators in one unit is very suitable for rotational applications in spacecraft. In the past, numerous studies focusing on the active actuator have been widely reported. However, few have addressed on the passive unit which is essential to the suspension system. In this paper, a sufficiently precise and concise analytical method which is based on the conformal transformation is proposed for the analysis and design of the HMB with specific axial load capacity. With this approach, important parameters used for optimal MB designing, such as magnetic leakage coefficient, as well as the flux density of main flux and fringing flux are given as simple formulas, which educe the axial restoring magnetic force and the axial passive stiffness. The coupling effect of these two units of the HMB is analyzed. The torque generated by the control current of the radial bearing is educed. Experimental investigation via an experimental apparatus to measure the axial specific capacity is introduced. Flywheel prototypes suspended by this kind of HMB system are tested, and the consequence is compared with the analytical data and the finite-element method data to get a final conclusion, which demonstrates the specific load capacity and the conciseness and accuracy of the analytical method.