Analysis of a Novel Coil Design for Axial Flux Machines
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- Institutt for elkraftteknikk 
A novel coil design for permanent magnet axial flux machines is presented. An analysis of its performance regarding winding layout, cooling capability, cogging torque, and back-EMF is conducted. Different manufacturing and assembly methods are described. A prototype stator has been built and tested. The prototype stator has a 90% fill factor, and is an iron free wave-winded topology. The prototype has been analyzed using analytical approaches, and compared to the performance in the laboratory testing. An analysis of introducing iron in the stator has been done, where the effect of iron stator is compared to the iron free prototype. An analytical model describing the performance of the iron stator has been developed and presented in this thesis. The model is used to present its performance in industrial applications, where high torque - low speed properties are needed. The results show that this design may compete with hydraulic motors in the industry, having an extremely high torque density, but due to high current densities, an efficiency of 30% to 40%. An investigation of the cooling capability of the coil design has been conducted by master student Lars Johan Clad at the Department of Energy and Process Engineering at NTNU. It has here been proved that the cooling of this coil design is sufficient to enable a current density of 20A/mm^2 in the stator conductors, with only 60% operating temperature.