Stator Magnetic Field Analysis of a Spherical Induction Motor Using Soft Magnetic Composites

A spherical induction motor has a simple structure and the same moment of inertia in all directions, which is helpful to reduce the speed fluctuation and the difficulty of the control system design. Soft magnetic composites(SMCs) have advantages of low loss, suitability for a three-dimensional magnetic circuit design, easy processing, and low cost. The stator magnetic field analysis method of an SMC spherical induction motor was studied. First, according to the symmetical arrangement of stator coils in the space, a research strategy was proposed, which synthesized the whole magnetic field of the spherical motor by the magnetic field of the single-coil group. The feasibility was verified by analyzing the equivalent magnetic circuit of the single-coil group. Second, the 3D magnetic field of the coil group was simplified to a 2D model. Thereafter, the equivalent magnetic network model was established, and the distribution of the air gap flux density was solved. The whole stator magnetic field of the motor was obtained via the rotation transformation of the spherical harmonic coefficient(SHC). The average relative errors between the equivalent magnetic network model and the finite element simulation models of 3D and the 2D magnetic field of a single couple of the coil are 13.34% and 18.53%, respectively. The relative error is less than 4.50%, where the magnetic density is large, so that the accuracy of the equivalent magnetic network model was verified. The hardware and software experimental platforms of the prototype were built, and the air gap magnetic flux density of the prototype in different conditions was obtained. The experimental results showed that the magnetic field characteristics of the prototype were consistent with those of the theoretical analysis, verifying the correctness and the practicability of the stator magnetic field analysis method. © 2022 Tianjin University. All rights reserved.