Low speed high torque PMSM design based on unequal teeth structure

To satisfy the requirement of the low speed high torque permanent magnet synchronous motor (PMSM) used in the precise numerical control (NC) rotary table, the multipolar PMSM with similar pole number and slot number and unequal teeth structure is designed in this paper. This kind of motors can operate with lower speed, and the structure of similar pole number and slot number can reduce its inherent cogging torque ripple effectively. The unequal teeth structure maximizes the stator teeth flux linkage and winding synthesis coefficient. As a result, the average torque is increased. The finite element method (FEM) software ANSYS is employed to analyze the proposed motor. The ANSYS calculation results prove that the cogging torque ripple of the proposed motor is 1.05% of its rated torque, and the unequal teeth structure can increase the average torque by 5.26% compared with the equal teeth one with the same motor parameters. Meanwhile, the prototype has been designed, produced and tested. And the experimental results also prove that the design method in the paper is correct and effective.