Flux Focusing Effect within the Segmented Stator of an Axial Flux Machine

Inhalt:
The market for light electrical vehicles and especially electric bicycles is steadily increasing. Distinct space limitations and low budgets for the electric motor require new approaches for a cost-efficient production. In this context, the modu-larization of the stator structure appears as a promising approach. It leads to small parts, which reduce the cost of transport, storage and production tools. This work investigates the design of an axial flux machine, which comprises a segmented stator made of SMC (Soft Magnetic Composite). In contrast to conventional machines, the stator iron is not coherent. Instead, small gaps between the iron parts lead to special electromagnetic effects, including a focusing of the rotor flux. The analytic part of this work deals with the magnetomotive force distribution and its dependence on the stator structure. Based on the conclusions, an optimized stator segmentation concept is derived. It is shown that the number of turns in series per phase is halved and therefore the copper losses decrease significantly. Concurrently, the winding factor is increased to a value greater than one. The work ends with the presentation of a prototype, which drives an electric bicycle.