Analysis and comparison of classical and flex-PCB slotless windings in BLDC motors

Slotless brushless DC motors find more and more applications due to their high performance and their low production cost. This paper focuses on the windings inserted in the airgap of these motors, and particularly, to an original production technique which consists in printing the windings on a flexible printed circuit board. It shows that this technique, when coupled with an optimization of the winding shape, can improve the power density of about 30 % compared with classical skewed and rhombic windings made of round wire.