Abstract: To solve the contradiction between axial dimension and precision of magnetic bearing system, the magnetic force characteristics of a novel permanent magnet biased axial magnetic bearing which integrates rotor radial torsion with axial translation control function is researched. Equivalent magnetic circuit method is used to carry out modeling of magnetic circuit of magnetic bearing. Integral calculation formula of magnetic force of magnetic bearing is given on the basis of the magnetic circuit model, the magnetic force characteristic curve of the closed-loop system of magnetic bearing is obtained. The analysis on the magnetic bearing used on a flywheel shows that there exists good relationship between the magnetic force of magnetic bearing and the magnetic pole air gap and control current, and all the control channels are approximately decoupled. Compared to the typical magnetic bearing structure, the proposed one helps to improve the control accuracy and reduce the axial dimension of the magnetic bearing system. It is suitable for magnetic suspension flywheel system.

Key words: Axial magnetic bearing, Equivalent magnetic circuit, Integral method, Magnetic force characteristic, Permanent magnet bias