Comparison of Stator Winding Technologies for High-Speed Motors in Electric Propulsion Systems

The stator winding is known to be a key factor to enhance the performance of electrical machines in terms of efficiency, lifetime, volume and consequently the costs. Therefore, the selection of the suitable winding technology and a proper design are mandatory to fulfill the challenging requirements defined by transportation electrification. The paper deals with the comparison of stator winding technologies to be used for high speed electrical machines for propulsion applications. The most commonly used winding configurations in automotive applications such as stranded wire and hairpin are compared with an innovative winding solution featuring formed litz wires. The analysis is carried out by comparing the main figures of merit such as the phase resistance, the AC loss factor and the thermal behavior of the different winding configurations. The reference machine explicitly designed for the analysis is a 24 krpm Permanent Magnet assisted Synchronous Reluctance Machine featuring a peak power of 200 kW. The performance assessment, supported by analytical and numerical electromagnetic and thermal simulations, highlights the main features of each design solution.