Performance Improvement of Brushless Wound Rotor Vernier Motor for Washing Machine Applications

Abstract

This paper presents the design and performance analysis of a brushless wound rotor vernier machine (BLWRVM) for variable speed applications, particularly in the context of domestic appliances like automatic washing machines which have two cycles of operation: the wash cycle at low-speed and dry-cycle at high-speed. The proposed BLWRVM utilizes a different winding configuration that enhances the performance compared to the existing reference machine. The machine topology uses a dual winding setup on the stator, a 3-phase main ABC1 winding and a 1-phase additional A2 winding on the stator, specifically engineered to generate both fundamental and subharmonic components of MMF in the airgap of the machine. In order to achieve the brushless operation, the additional excitation winding is placed on the rotor which is connected through a rectifier to the field winding. The voltages are induced in this excitation winding using the MMF’s sub-harmonic component. These AC-induced voltages are rectified by a rotating rectifier placed on the rotor periphery and are then supplied to the main field winding. A 4-pole, 24-slot stator and 44-pole 44-slot outer rotor machine is designed. The fill factor of the machine’s stator slot was then increased to 35% and the rotor’s slot fill factor was increased to 30%. Furthermore, different skew angles of the rotor were analyzed to find the optimal skew angle that yields minimum torque ripple. The performance characteristics were compared with a reference BLWRVM. To validate the design a 2D-FEA was carried out to find out the performing characteristics of the proposed machine and reference machines using ANSYS Electromagnetic suite version 2022 R1.