Hybrid-Strand Winding Topology With Improved Power Density in Automotive Electric Machines

Abstract

The rectangular profile conductor with a large cross section requires less slot space and has better heat dissipation ability than the traditional round profile one. But its application in automotive propulsion electric machines is thwarted by high ac winding losses and temperature rise under high-speed operations. This article proposes a novel stator winding topology with hybrid strands based on the ac losses' distribution characteristics and the theoretical relationship between the eddy current suppressing ability and the geometric parameters. The new winding can effectively reduce the ac loss and the peak temperature in the winding at high-speed operation. Meanwhile, it can maintain a high filling rate. Therefore, the machine's maximum rotating speed and power density can be effectively improved. In experimental validation, a winding sample with this new topology is manufactured and compared with the conventional one formed by rectangular wires. It shows the proposed method can reduce the winding ac loss by up to 12% and the temperature rise by 10–21%. It is validated to have considerable industrial potential in the future development of automotive motors.