On the stator design of an axial flux permanent magnet synchronous traction machine for aerospace applications

Abstract

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.