Winding Design for Minimum Power Loss and Low-Cost Manufacture in Application to Fixed-Speed PM Generator

This paper presents the results from a coupled thermal and power loss analysis of an open-slot permanent-magnet (PM) generator. The research focus has been placed on the winding design providing minimum power loss at an ac operation, together with low-cost manufacture. The analyzed PM generator is intended to operate at a fixed speed, allowing for the winding design to be finely tuned for a single operating point. Such a design approach has not been widely reported in literature, and the existing body of work is largely focused on variable-speed applications, where the winding design is a compromise between the low-speed and high-speed operating points for a given torque-speed envelope. The ac winding power loss has been analyzed for several winding variants with different conductor dimensions, accounting for the winding operating temperature. The calculated results suggest that, in the analyzed PM generator, a lower winding slot fill factor is preferable as compared with the more common approach, where the highest manufacturable winding slot fill factor is usually considered. The power loss predictions have been supplemented with the thermal analysis of the complete generator assembly for the winding variants considered, illustrating the importance and influence of the appropriate winding design on the power output capability of the fixed-speed PM generator. The most promising winding design for the minimum power loss at a rated operating point has been downselected for prototyping. The theoretical findings from the analysis have been compared with the experimental data from hardware tests on a stator winding section, showing close agreement.