Analytical Approach to Understanding the Tooth Height Variations of the Stator in an Axial Flux Machine and its Impact on the Airgap

Abstract: Höganäs AB is developing an axial flux machine, where an even airgap between the stator and rotor is a vital parameter when designing a well functioning machine. It is believed that the stator is the component that introduces the biggest variations to the airgap, and that is why the stator is the object of investigation for this thesis. The stator is made of metal powder and the steps in the manufacturing process are pressing and heat treatment. As a result of the project it is concluded that the measuring fixture for stator components in use at Höganäs today affected the components before they are heat treated. Therefore a new reliable measurement fixture was introduced. The result of optimizing the press settings did not improve the flatness of the stator coreback, but the evenness of the teeth were improved. The result is pointing in the direction of that the heat treatment method used today, is the best of the different variations that were included in this report. It was concluded that if crimping is to be considered as an attachment method for the stator to the aluminum housing, it needs to be investigated further. Results showed how the stator deforms during the force, and that the magnetic properties are affected. The results regarding cogging were setback by too many introduced variations in the assembly. Because it was not possible to, in a confident way, draw any conclusions from the different stator groups. However, the data presents that two out of the twelve combinations that were tested, shows different and better result than the rest.