Fast Sizing Tool and Optimization Technique for Concentrated Wound Slotless Outer Rotor Motor for eVTOL Application

This paper aims to present the feasibility and advantages of slotless motors for electric aircraft applications. Currently, eVTOL (electric vertical takeoff and landing) aircraft are equipped with a slotted motor with concentrated windings and an outer rotor with strong magnets. Slotless machines with Halbach array can offer significant advantages over traditional slotted machines. Instead of using the round conductor, this paper is focused on the slotless coils made up of stranded copper strips, which leads to a low inductance machine. Furthermore, employing a drive made up of wide bandgap semiconductors enables slotless technology. The paper presents analytical modelling of the slotless machine and compares different groupings of the concentrated winding for the same number of poles. This analytical model is coupled with the optimization tool to find the most power-dense design, and these designs are validated with the commercially available FEA software to demonstrate the accuracy of the proposed method.