Inclining-Interface Connected Integrated-Parallel-Magnetization Trapezoidal-Magnetic-Pole Combination BPMSM and Its Magnetic Field Analytical Calculation

For the bearingless permanent magnet synchronous motor (BPMSM), to improve the sinusoidal degree of air-gap magnetic field, and solve the problem of difficulty in solving the air-gap magnetic field, a novel structure of Inclining-interface Connected Trapezoidal-Magnetic-Pole Combination with integrated Parallel Magnetization (ICTMPC-PM) is proposed, and for the BPMSM with ICTMPC-PMs, the analytical calculation model of the no-load air-gap magnetic field is studied under the consideration of the rotor eccentricity. First, the analytical equation of air-gap flux density for the slotless BPMSM with ICTMPC-PMs is obtained by solving the Laplace’s and the Poisson’s equations in each subdomain. Then, combining the relative permeability function, the analytical equations of radial air-gap flux density are further solved for the slotted BPMSM with ICTMPC-PMs. Subsequently, combining with the equivalent air-gap function, and under the consideration of the radial eccentricity of the bearingless rotor, the analytical equations of radial air-gap flux density are achieved. Finally, through the finite element method (FEM), the characteristic comparison of no-load air-gap magnetic field and the validation of analytical calculation model for a BPMSM with ICTMPC-PMs are conducted. From the research results, the BPMSM structure with ICTMPC-PMs can significantly reduce the low order harmonics of the air-gap magnetic field, such as the 3rd, 5th, and 7th harmonics, thereby significantly improve the sinusoidal degree of the air-gap magnetic flux density waveform; The established analytical calculation model of air-gap magnetic field for the BPMSM with ICTMPC-PMs is effective and has a high accuracy.