Analysis And Design Of Spherical Induction Motor Using Soft Magnetic Composites

A spherical motor can perform a three-dimensional motion at one point,which has compact structure and no singularity in the working space.Soft magnetic composite(SMC)has high resistivity,small eddy current loss and isotropy in magnetic and thermal,which is suitable for high-frequency motor with complex structure and three-dimensional magnetic circuit design.In this thesis,a new SMC spherical induction machine is presented.The magnetic field is analyzed using the equivalent magnetic network method.The machine parameters are optimized using a multi-objective particle swarm optimization:Firstly,the structure of the motor with SMC at the stator yoke,rotor and stator tooth was adopted and the working principle of the motor is introduced.The arrangement of stator coils is proposed based on the subspherical harmonic structure of Y32 order.Based on the symmetry of the spatial distribution of the motor structure,a method that simplifies calculating the whole magnetic field of the spherical motor by using the rotation transformation of the single coil magnetic field based on the spherical harmonic coefficient is proposed.Finally,the split-phase electrification strategy of the rotating magnetic field with Y32 type that produced by spherical motor is studied.Secondly,a method is proposed which transforms a three-dimensional magnetic filed of the spherical motor with a single couple of coil into a two-dimensional magnetic field model of a single couple of coil,and the equivalent magnetic circuit network model(EMCN)is established by meshing the two-dimensional magnetic field model of a single couple of coil.The expressions of magnetoresistance and magnetodynamic potential are derived,The air gap magnetic field density distribution of the equivalent magnetic circuit model is obtained by the mean magnetic energy method.The validity of the equivalent magnetic circuit network model is verified by comparing the finite element simulation results of the spherical motor that has a single couple of coil and the twodimensional magnetic field model of a single couple of coil.The simplified 2D magnetic field model can reduce the data of 3D magnetic field calculation and improve the calculation speed.Thirdly,a multi-objective Particle swarm optimization based on the equivalent magnetic network model is used to optimize the dimensions of the spherical motor that has a single couple of coil.By analyzing the size of SMC standard block,processing conditions and motor structure,the optimum variables and their ranges are determined.The optimum objectives are the minimum motor mass,the maximum proportion of the third-order spherical harmonic coefficient and the maximum amplitude of the third-order spherical harmonic coefficient.Then,the Pareto optimal solution and the size of the optimized motor are obtained.The correctness of the optimization is proved by comparing the indexes before the optimization.Finally,the whole magnetic field of the optimized motor is analyzed with the split-phase strategy,which shows that the optimized design can make the motor produce larger rotating magnetic field of Y32 type with smaller mass.Finally,according to the size and material characteristics of SMC standard block,the stator yoke block,rotor block,stator tooth block and other workpiece models of the spherical induction motor are designed.The air gap magnetic flux density of the prototype under different working conditions was measured with the hardware and software experimental platform of the prototype built The experimental results show that the magnetic field characteristics of the prototype are basically consistent with the theoretical analysis and meet the design requirements.