Manufacturing of Conically Shaped Concentrated Windings for Wheel Hub Engines by a Multi-Stage Upsetting Process

In case of wheel hub engines, the coil installation space is limited by the rim diameter and width. Due to their shape and a small end winding, conically shaped concentrated windings offer the possibility of increasing the torque density of wheel hub engines. After comparing different concepts, a multi-stage upsetting process seems to be suitable for an economical series production of these windings. In this paper a multi-stage tool, which allows for production of prototype windings from a pre-bent semi-finished product, is presented. The formability of enameled copper wires and the need for adjustment of the semi-finished product and the tool are investigated. Forming tests of first prototype coils show a necking of the deformed windings due to material flow in longitudinal direction of the wire. By adjusting the geometry of the semi-finished product, necking can be reduced. In addition, an adjustment of the prototype tool is presented, which allows for a narrowed cycle time of the upsetting process.