Magnetic circuit designing and structural optimisation for a three degree‐of‐freedom hybrid magnetic bearing

Abstract

The three degree‐of‐freedom (3‐DOF) hybrid magnetic bearing (HMB) sets radial, axial at one entirety, which can effectively save the bearing installation space. Here, a 3‐DOF HMB is designed, optimised, and tested for a 30 kW 60,000 r/min high‐speed motor system. The radial and axial bearing capacity is analysed by equivalent magnetic circuit method and three dimensional finite element model (FEM) of initial model of 3‐DOF HMB is established. Then, the radial bearing capacity, axial bearing capacity, current‐stiffness, and displacement‐stiffness are selected as the optimised design target by using chaos particle swarm optimisation algorithm. Meanwhile, the axial length, eddy‐current loss, and air‐gap flux density are selected as constraints of optimization. The optimal results showed that the axial length is decreased, the eddy‐current loss is reduced, and the harmonics in the air gap is lower while the bearing capacity is improved. Furthermore, a 30 kW 60,000 r/min high‐speed motor with proposed 3‐DOF HMB is manufactured, and the experiments of the radial/axial static bearing capacity test, dynamic performance of high‐speed motor with no load in 60,000 r/min and with load in 55,000 r/min are carried out. Experiment results show that the optimised 3‐DOF HMB has good force performance and dynamic performance.