Multi-objective Optimization of a Combined Radial-Axial Magnetic Bearing for Magnetically Suspended Compressor

The combined radial-axial magnetic bearing (CRAMB) with permanent magnet (PM) providing bias magnetic flux is designed for magnetically suspended high-speed electromotor in the compressor for its compact construction. In this paper, the design principle and the initial model of CRAMB are introduced. To improve the performances of CRAMB and better meet the engineering requirements, the optimization is conducted on the bearing. Considering the incompatible objectives of the optimization model, the method of multiobjective optimization (MOO) on the bearing is proposed, which can balance these objectives compared with single-objective optimization (SOO). The objectives and constraints are provided in the form of analytical expressions by means of equivalent magnetic circuit whose rationality is demonstrated by finite-element method (FEM). To optimize the bearing efficiently, the integrated optimum methodology is adopted. After MOO process, the synthetical performances are improved, which are verified by FEM and experiment.