A Study on Design of Outer Rotor Spoke-type PMSM to Improve Power Density

Abstract

In the past, washing machine delivered torque between the motor and the load through power transmission mechanisms such as belts and gears. This leads to problems such as deterioration of washing power, waste of energy, increase of noise and belt wear. This leads to problems such as deterioration of washing power, waste of energy, increase of noise and belt wear. In order to solve these problems, recently, it has been changed to a direct drive (DD) system in which a motor and a load can be directly connected and driven. This study deals with the design of an outer rotor spoke-type permanent magnet synchronous motor (PMSM) that can achieve high power density and high efficiency compared to conventional PMSM after analyzing PMSM of home washing machine which is currently in use. In order to accomplish this research goal, the outer rotor surface permanent magnet synchronous motor (SPMSM) used as the DD motor for washing machine was designed based on the load demand speed-torque curve and the power characteristics were confirmed. Then, the outer rotor spoke-type PMSM was designed based on design conditions of the outer rotor SPMSM such as the voltage, current limitation, the same motor material, the air gap, the combination of number of poles and slots. The design direction of the motor that reduces the volume while maintaining the same power is established, and the torque ripple reduction and the design for improving efficiency are performed in parallel. The results of this study are expected to be useful not only for the design of electric motors for electric washing machine but also for high power and cost reduction.