Eddy Current Loss Analysis And Structure Optimization Of Permanent Magnet Spherical Motor

The spherical motor with permanent magnet (PM) not only makes the size of the spherical motor smaller, but also greatly improves the operation efficiency and controllability. Most PM in spherical motor’s rotor is made of neodymium iron boron materials, which has good magnetic properties, the higher remanent flux density and coercive force than other materials. But its heat resistance is poor and its conductivity is relatively high, the alternating magnetic field in air gap would make the PM temperature higher, and the magnetic properties would decline. All of above would affect the normal work of the motor. Permanent magnet spherical motor is still in the initial stage of theoretical research. This paper mainly focuses on the eddy current loss of PM in the permanent magnet spherical motor, and the main work is as follows:1. Based on the basic principle of eddy current loss in the permanent magnet pole of the spherical rotor, the analytical formula of eddy current loss in the permanent magnet is derived.2. The finite element 3D simulation model of the permanent magnet spherical motor is designed, The air gap magnetic density distribution and the harmonic distribution are obtained under different latitudes radial. The no-load stator coil EMF with rotation, flux linkage, the reluctance torque and eddy current loss generated in permanent magnets are analyzed. By changing the yaw angle of spherical rotor, the no-load eddy current loss with rotation is obtained in different yaw angle.3. The concept of the smallest element is proposed, and the inverse potential, flux linkage and eddy current loss characteristic curve are obtained in the smallest element solution domain. The error of the smallest element method is analyzed.4. The radial magnetic density distortion of air gap and eddy current distribution of the PM under different relative position between electric stator winding and rotor permanent magnet poles is analyzed.5. In order to reduce the rotor eddy current loss, the air gap length, PM radius, PM magnetization method, PM shape and PM segmented superposition are optimized for the spherical motor design.