Friction torque of thrust ball bearings lubricated with wind turbine gear oils

Planetary gearboxes used in wind turbines very often have premature bearing and gear failures, some of them related to the lubricants used. Five fully formulated wind turbine gear oils with the same viscosity grade and different formulations were selected and their physical characterization was performed. The lubricant tribological behaviour in a thrust ball bearing was analyzed. A modified Four-Ball Machine was used to assemble the bearings. They were submitted to an axial load and the tests were performed at velocities ranging between 150 and 1500 rpm. Experimental results for the operating temperatures and for the internal friction torque are presented.

► Five wind turbine gear oils were selected. Density and viscosities were measured. ► Frictional behaviour of a thrust ball bearing (51107). ► A modified Four-Ball Machine was used and tests were performed between 150 and 1500 rpm. ► Operating temperatures and internal friction torque, power loss and heat evacuated are presented. ► Rolling and sliding friction torques were determined.