This paper focuses on the study of the load-independent power losses generated by a complete planetary gearbox having a rotating ring gear and a fixed planet carrier. First, different configurations are studied to characterize the various losses such as those associated to bearings. The power losses generated by the complete gearbox is then measured thanks to a dedicated test bench. Those tests enable to determine a power loss distribution that is then validated using a thermal network analysis. Once the windage and the oil churning losses are estimated, their evolution with rotational speed and oil flow rate is investigated. The study reveals that the windage power losses, generated by the reduced scale planetary gearbox studied, do not increase with the cube of the rotational speed within the tested speed range. The oil churning losses evolve linearly with the oil flow rate and quasi linearly with speed. Finally, the evolution of the power loss distribution with respect to the rotational speed is presented.
Winger et al. (2026) studied this question.