Simplified calculation for the radial levitation force of radial-type superconducting magnetic bearing

It is usually difficult to obtain the radial levitation force of the radial-type superconducting magnetic bearing (SMB) due to the massive numerical calculations and the sophisticated experimental measurements. This study presents a method for fast calculating the radial levitation force of radial-type SMB, which is based on the infinitesimal method and the 2D finite-element method. During the modelling, the radial-type SMB is assumed to be composed circumferentially of infinite superconductor-permanent magnet (SC-PM) infinitesimals with shape of rectangular thin slice. The dependence of levitation force for the SC-PM infinitesimal on the air-gap length between the SC stator and the PM rotor can be obtained using the 2D finite-element model established in Cartesian coordinate system. Moreover, a simplified analytical model of calculating radial levitation force is developed based on the infinitesimal method and the circumferential distribution formula of non-uniform air-gap when the PM rotor exhibits radial eccentricity. The results of theoretical calculation and experimental measurement of radial levitation force show a good agreement, which verifies the feasibility of the proposed method. It has the advantages of fastness and easiness, and can be used as a theoretical tool for the design, optimisation and performance prediction of the radial-type SMB.