On the Optimal Design of Coreless AFPM Machines with Halbach Array Rotors for Electric Aircraft Propulsion

This paper presents and evaluates the optimal design of a coreless axial flux permanent magnet (AFPM) motor for electric aircraft propulsion. Ferromagnetic cores are entirely removed from the machine's structure to improve the specific power density and efficiency. An approach for envelope design optimization of the proposed motor is introduced, considering the polarity as an independent variable and employing an evolutionary algorithm and 3D Finite Element Analysis (FEA). In addition to the proposed electric motor's electromagnetic performance, fault-tolerant capability and thermal management are considered in the optimization procedure. The optimization results and similar studies from power electronic and thermal management subsystems can be used to reach the system-level optimal performance. The optimization results are discussed through the evaluation of objectives' behavior and variables' trends toward the optimal design. It is shown that pole number and magnet-to-magnet gap are the essential geometric variables since they impact the active mass and efficiency of the machine, respectively.