A hybrid winding design to reduce AC losses in electrical machines with bar conductors

Bar conductor windings with rectangular cross-sections are increasingly used in electrical vehicle traction applications for their high slot fill factor, reduced losses, improved heat transfer, and manufacturing repeatability. However, AC losses from eddy currents due to skin and proximity effects limit their performance at high frequencies. This paper proposes a hybrid winding design to reduce AC losses in electrical machines with bar conductors. The design integrates copper conductors with outer layers of low-conductivity materials, such as aluminium or brass, to leverage the low DC resistance of copper and mitigate AC losses caused by skin and proximity effects at high frequencies. A comprehensive analytical model and finite element analysis are developed to optimize and validate the design, supported by experimental results from brass-copper hybrid conductors. The proposed design reduces winding losses without altering the original winding layout, providing a practical and efficient solution for enhancing the performance of traction machines.