Improved Method for Calculating Armature-Reaction Field of Surface- Mounted Permanent Magnet Machines Accounting for Opening Slots

This paper presented an improved analytical method for calculating armature-reaction field in the surface-mounted permanent magnet machines accounting for opening slots. The analytical model is divided into two types of subdomains. The current of the armature is centralized in the center of the slots. The field solution of each subdomain is obtained by applying the interface and boundary conditions of the model. Two 30-pole/36-slot prototype machines with different slot-opening width are used for validation. The FE (finite element) results confirm the validity of the analytical results with the proposed model. The investigation shows that the wider the slot-opening width is, the smaller the peak value of radial and circumferential components of flux density, and the analytical armature-reaction field produced by centralized current in the slots is similar with the armature-reaction field produced by distributed current in the slots in the FE.