Simulative investigation of interactions of torque and non-torque loads of a WT gearbox regarding planet carrier bearing ring creep
Pascal Bußkamp
Summary
A critical cause of damage to roller bearings in wind turbines (WTs) is ring creep, which may result in cost-intensive replacement of the main bearing or gearbox. Ring creep is the relative movement between bearing ring and shaft (or housing) and is caused by an accumulation of micro-slip over the service life. With increasing torque density of modern WTs, more micro-slip and thus more ring creep can be expected due to the increase in deformation caused by reduced wall thicknesses. To reduce the occurrence of costly component replacements and thus to reduce the levelized cost of energy, the robustness of modern WTs against ring creep must be increased. To increase the ring creep robustness of WT bearings, a better understanding of ring creep considering the system behavior is required. In modern gearboxes (> 3 MW), the planet carrier bearing (PCB) on the rotor side is prone to ring creep. This work focuses on PCBs with D ≥ 1200 mm, as these dimensions are typical for modern WTs. For the simulative investigation, a ring creep simulation model based on a test bench is presented, enabling subsequent validation. The simulated stress distributions and ring creep curves indicate counteracting influences of non-torque loads and torque. The non-torque loads significantly influence the rolling element forces and thus rolling element induced ring creep. In contrast, structure-induced ring creep occurs in opposite direction, caused by the planets rotating under torque load. Thus, the resulting ring creep behavior depends on the interaction of both load types, which is shown in this work for different variations of the planet number, torque and non-torque loads. These results can be validated experimentally in future work, as the simulated test bench is being built based on a simplified generic drivetrain (~3.3 MW) and enables force application in all six degrees of freedom.