A Study on Axial Type Servo Motor for Current Density and Torque Ripple Reduction through Magnet Shape

Abstract

PMSM is used in various fields such as industry, military, and precision control like medical. Axial type motors driven through axial magnetic flux have high power density and geometrical advantages differentiated from radial type motors. However, the axial type motor has the disadvantage of having a large torque ripple. Therefore, the axial type motor may be disadvantageous in a field requiring high precision, such as a servo motor. This paper is about the improved design of the axial type servo motor. In general, since the current density is proportional to the heat loss, it is necessary to reduce it. Selecting a high magnetic load by increasing the motor diameter, the current density can be lowered. However, the torque ripple tends to increase cause to diameter. Therefore, to reduce torque ripple, a methods of giving a pole ratio to a permanent magnet and applying halbach structure are presented. And by comparing the output characteristic according to the two methods, the design was carried out through a structure with better performance.