A non-uniform load distribution model has been used to accurately account for the varying gear tooth loads at the planet-sun and planet-ring mesh.

Spin losses increase with increasing speed, with windage drag dominating over oil churning losses for the considered application example. However, it appears that using a combination lubrication system in wind turbines does not affect the efficiency since spin losses are several orders of magnitude lower than mechanical loses in low-speed wind turbine transmissions.

The use of combined lubrication system improves lubrication at the gear and bearing contacts as it allows hydrodynamic lubrication to occur so as to prevent possible metal-to-metal contacts.

Increasing bearing mean diameter acb88d932999202948def0157e9" title="Click to view the MathML source">d_m$d_m$ results in an increase in mechanical and spin power loss. Planet bearing design should be conducted simultaneously with planet gears so as to help chose a beneficial design based on combined efficiency and fatigue requirements but not solely for fatigue purposes.