Analytical model of the magnetic field distribution of a generator combined with magnetic bearing in wind turbines

Abstract

To achieve radial suspension and eliminate the effect of rotor gravity in wind turbines, a novel structure of a generator combined with a magnetic bearing (GCWMB) is proposed in this paper. The GCWMB not only has the characteristics of the traditional permanent magnet (PM) generator but also has the advantages of reducing friction and starting wind speed, eliminating rotor gravity. The structure and principle of the GCWMB are analyzed in this paper. To improve the calculation accuracy of ux density, an analytical model based on the Fourier series decomposition is proposed to establish the model of ux density in the outer air gap. Taking into account the edge effects and the eccentricity of the rotor, an improved equivalent magnetic circuit method is adopted to model and analyze the ux density in the inner air gap. The effectiveness and correctness of the proposed analytical model in the outer and inner air gaps are verified by finite element analysis (FEA) and experiments.