Investigation of Axial Carrying Capacity of Radial Hybrid Magnetic Bearing

This paper investigates the axial carrying capacity of a new radial hybrid magnetic bearing (RHMB) using experimental, finite element, and magnetic circuit methods. The thrust bearing of traditional structures is not included because an axial resilience is generated by this new RHMB when the rotor is axially displaced. The relationship between axial resilience and displacement is tested, from which the axial passive stability stiffness is derived. The passive stability stiffness linearly decreases with increased displacement. Based on the 2-D and 3-D finite element models of RHMB established with AYSYS software, the axial resilience is calculated and compared with the experimental results, which shows that the numerical results are fully consistent with the experimental ones. The influence of structural dimensions to the axial resilience, including air gap length, permanent magnet sectional area and height, and magnetic pole board height, are analyzed in detail based on the 2-D model. The formula to calculate the axial resilience suitable for different lengths of air gap is deduced by the magnetic circuit method. Theoretical results calculated by this formula are in good agreement with the experimental and numerical results. The conclusions are helpful in designing and controlling RHMB.