Feasibility of a new ironless-stator axial flux permanent magnet machine for aircraft electric propulsion application

With the development of aviation electrification, higher demands for electrical machines are put forward in aircraft electric propulsion systems. The aircraft electric propulsion requirements and propulsion motor features are analyzed in this paper. Comparing with conventional PM machines, ironless stator axial flux permanent magnet (AFPM) machine topologies with Litz wire windings allow designs with higher compactness, lightness and efficiency, which are suitable for high-frequency and high-power density applications. Based on the motor requirements and constraints of aircraft electric propulsion systems, this paper investigates a high-power 1 MW multi-stack ironless stator AFPM machine, which is composed of four 250kW modular motors by stacking in axial. The design guidelines and special attentions are presented, in term of electromagnetic, thermal, and mechanical performance for the high-frequency coils and Halbach-array PM rotor. Finally, an ironless stator AFPM motor is manufactured, tested and evaluated with the consideration of cost and processing cycle. The results show that the output power is up to 53.8kW with 95% efficiency at 9000r/min at this stage. The proposed ironless stator AFPM machine with oil immersed forced cooling proves to be a favorable candidate for application in electric aircraft as propulsion motors.