Multi-disc axial flux stratospheric aircraft propeller drive

The stratospheric unmanned aircraft for the proposed European Union Helinet telecommunications infrastructure will use inverter/brushless AC motor drives for the propellers. One form of machine being considered is of multi-disc axial flux slotless construction. This has no iron losses due to the fundamental field but, since the windings are in the air-gaps, eddy current losses are present in the strands of the coil conductors. These losses are calculated, using a finely meshed finite element model and a time-stepped approach. The winding factors of the three types of winding without coil end-region overlaps are determined. Design comparisons are drawn between axial flux and conventional radial flux designs.