Analysis and optimization of a modular stator core with segmental teeth and solid back iron for pm electric machines

Compared with conventional overlapping windings, nonoverlapping windings offer an exclusive advantage of short end-windings, which leads to less copper loss, shorter axial length, and higher slot fill factor particularly when used with segmental stator core. However, it is not so easy to manufacture the stator with nonoverlapping windings, especially when a high slot fill factor with low cost is required. In most existing methods, laminated segments are connected directly to form a complete stator core, so-called laminated-joint core. This requires precise mechanical assembles, and usually results in restrict process with expensive equipments. The goal of this paper is to propose a new segmental stator structure without laminated-joint, where the laminated tooth modules are coupled with a solid back iron. In this paper, existing manufacturing methods of segmental stator core will be reviewed and analyzed. Subsequently, several models are developed and improved, step by step, to achieve the best target, especially taking the iron losses as an evaluation criterion. Some techniques to reduce iron losses in the solid back iron will be proposed and compared. Some practical issues for manufacturing the proposed segmental stator core are discussed. Influence of subsidiary air gap on the iron losses will also be analyzed. And, cost evaluation of the proposed method, as well as the realistic shapes of laminations-solid-joints, is presented.