Full Analytical Model of AC Copper Losses in Hollow Conductors of High-Speed Electric Motors

In the current context of a demand for high-efficiency and high-performance motors, ac copper loss is a key factor limiting the power density improvements of high-speed motors. Due to the interaction of multiple factors affecting ac copper losses, there is a lack of comprehensive and consistent understanding of the loss mechanism. Moreover, existing analysis methods face limitations in either computational efficiency or result accuracy. To address this, this study proposed a fully analytical model for hollow conductor ac loss, derived from a detailed analysis of magnetic and current distributions within hollow conductors under high-frequency armature and air-gap magnetic fields. It also examines the correlation between the armature ac copper loss and induced ac copper loss. The model accounts for the nonlinear effects of the iron core by incorporating an anisotropic equivalent magnetic permeability. The model accuracy was verified under various magnetic field settings and hollow structure designs, with errors within 4% and 6% in comparison to simulation and experimental data, respectively. This study enhances understanding and computational precision of ac copper loss in high-speed motors and provides a refined model for performance analysis and optimization.