Aviation is one of the fastest growing methods of transportation, with passenger volumes expected to triple in the next twenty-five years. It is also contributing an ever increasing share of global emissions. One of the highly effective ways to reduce emissions in aerospace is through electrification. This is already underway with the development and adoption of More Electric Aircraft. A next step is the development of hybrid propulsion, or all electric aircraft, with electric propulsion systems. In order to achieve this goal, the power density of the electric drive is of critical importance. Axial flux permanent magnet synchronous machines have been identified as one the highest power density machine types suitable for these electric drives. In this thesis, an axial flux permanent magnet machine is developed for an electric aircraft propulsion system. A review of electric machines in aerospace applications is conducted, followed by an overview of the design and simulation of axial flux machines, and a presentation of the machine under study. The primary objective of this thesis is to improve the stator design of the axial flux machine by reducing loss, weight, and volume. Magnetic materials are studied, and using grain oriented silicone steel for the stator teeth is shown to improve torque production of the machine. The wire, coil, and stator geometry are modified to reduce copper loss. A tightly spaced coil, axially centered on the tooth, with high aspect ratio wire and chamfered pole shoe is shown to reduce loss. Finally, a compact stator winding is proposed with coil terminations on the inner diameter of the stator. The proposed winding reduces the volume of the machine, as well as further reducing copper loss due to less wire utilized. These actions significantly improve the efficiency of the machine, while reducing weight and volume. / Thesis / Master of Applied Science (MASc)

Traffic congestion in large urban and metropolitan areas is a substantial problem plaguing these areas. Not only are commuters losing valuable time, but greenhouse gas emissions are substantially worse because of congestion. Considerable research and development into next generation electrified aircraft is ongoing to introduce air mobility as a viable new means of transporting people and goods across long commutes. This development extends into commercial aviation as a whole as a means of reducing the industry’s carbon footprint with new aircraft designs that employ electrified propulsion systems. Many electrified aircraft projects are currently underway, ranging from small commuter aircraft all the way to large twin-aisle aircraft, and part of the development scope for alot of these projects is creating highly robust and power dense electric machines that replace the current state-of-the-art. The axial flux permanent magnet synchronous machine is an exciting candidate for aircraft propulsion due to its exceptional torque density and compact axial nature. In this thesis, the mechanical design for three generations of axial flux permanent magnet synchronous machines is discussed. These machines serve as development phase prototypes for machines that are ultimately intended for propulsion applications in commercial aviation, particularly for eVTOL aircraft. The motivation for electrification in the commercial aviation industry is discussed, followed by an overview of the development landscape for electrified propulsion systems in commercial aviation, focusing primarily on electric machines that are currently state-of-the-art or are set to be in the near future, as well as what is required for future electric machines in terms of power output and power density. The axial flux architecture is then presented, including a high-level comparison to the radial-flux architecture, an overview of the various axial flux machine designs and topologies, and a discussion of the inherent mechanical design challenges associated with the axial flux architecture. The yokeless and segmented armature axial flux permanent magnet synchronous machine design was selected for the machines developed as part of the research for this thesis, and the discussion of the mechanical design of these machines is broken up into the two core sub assemblies: stator assembly and rotating assembly. High-level design methodologies are introduced for both sub-assemblies, which is further broken down into different approaches pertaining to each generation. The first and second generation designs are presented at a high level, followed by deep-dives into the complete mechanical design for the third generation stator, the bearing selection, arrangement, and analysis for the third generation rotating assembly, and adhesive characterization trials used to guide adhesive selection for rotor magnetics retention in the second and third generation machines. The current status of the machines and any outcomes from testing that has been conducted thus far, particularly with respect to performance, is presented at the end. / Thesis / Master of Applied Science (MASc)