Abstract. In this paper, the planetary load-sharing behavior and fatigue
life of different wind turbine gearboxes when subjected to rotor moments are
examined. Two planetary bearing designs are compared – one design using
cylindrical roller bearings with clearance and the other design using
preloaded tapered roller bearings to support both the carrier and planet
gears. Each design was developed and integrated into a
750 kW dynamometer tests, the loads on each planet bearing
row were measured and compared to finite-element models. Bearing loads were
not equally shared between the set of cylindrical roller bearings supporting
the planets even in pure torque conditions, with one bearing supporting up to
46 % more load than expected. A significant improvement in planetary
bearing load sharing was demonstrated in the gearbox with preloaded tapered
roller bearings with maximum loads 20 % lower than the gearbox with
cylindrical roller bearings. Bearing life was calculated with a
representative duty cycle measured from field tests. The predicted fatigue
life of the eight combined planet and carrier bearings for the gearbox with
preloaded tapered roller bearings is 3.5 times greater than for the gearbox
with cylindrical roller bearings. The influence of other factors, such as
carrier and planet bearing clearance, gravity, and tangential pin position
error, is also investigated. The combined effect of gravity and carrier
bearing clearance was primarily responsible for unequal load sharing.
Reducing carrier bearing clearance significantly improved load sharing, while
reducing planet clearance did not. Normal tangential pin position error did
not impact load sharing due to the floating sun design of this three-planet
gearbox.
Remarks on the Poisson stochastic process (III) (On a property of the homogeneous Poisson process)