Novel Optimized Shape and Topology for Slotless Windings in BLDC Machines

Slotless windings are commonly used in small size high-speed electrical brushless dc machines. Unlike slotted windings, forced to follow the direction of slots, slotless windings can be freely arranged in the airgap. This represents several opportunities for optimization. Nevertheless, very little research is performed in this domain. This article intends to challenge the traditional way of manufacturing windings. Indeed, most of the windings are made with isolated wire of constant section. However, it is demonstrated here that the performances of a motor can be significantly increased by optimizing the shape of the winding and by selecting nonconstant wire sections. A prototype of the new topology has been manufactured and measurements have demonstrated an increase of the motor constant from 18% to 24% compared to a traditional slotless winding.