Minimum Friction Losses in Planetary Stages of Wind Turbine Gearboxes

Abstract

Mechanical efficiency is not a critical design factor of wind turbine gearboxes since wind energy is abundant and costless. The design and sizing of the gears will be determined by the requirements of power density, gear ratio, fatigue safety, and allowable noise and vibration levels. However, reducing power losses results in lower lubricant heating, and therefore, a smaller cooling system is required with lower induced thermal stresses. Reducing friction losses will therefore be beneficial for the mechanical behavior of the gearbox. This paper provides a new method for the calculation of the optimal values of the outside radii and rack shift coefficients of planetary gear stages to minimize the friction power losses, maintaining unalterable geometrical and operating parameters that ensure the preestablished values of the aforementioned critical design factors.