Aerotorque WindTC shown to reduce overload and torque events that can lead to white etch area formation by 4x. High speed bearing life in 1.5MW gearbox could be improved by factor of 2x by avoiding WEA.
All wind turbines are affected by transient drivetrain loading events due to extreme wind and stops triggered by gearbox fault codes. As turbines have continued to grow larger and seek to produce more power out of the drivetrain, transient load events have increased.
Research and eld application have shown that the torque reversals and impact loads are a leading cause of White Etch Area (WEA) and axial crack damage. White etch/Axial cracks are a phenomenon in wind turbine bearings where super hard inclusions form in the inner raceway. Axial cracks and other damage in bearing raceways have become a major cause of premature gearbox failures, costing up to $250,000 to repair or replace the gearbox.
Aerotorque collected volumes of eld date on torsional reversals during turbine stopping and other events that produce some of the most dramatic torque reversals. The data showed Aerotorque’s WindTC product enabled a significant reduction – up to 54% in forward and 74% in reverse – in drivetrain loading, even on turbines with advanced controls. The issue was straightforward: how do you convert that to a life factor for customers to better calculate value and return on investment?
Aerotorque approached Sentient Science to use DigitalClone® to understand the difference in rolling contact fatigue life from torsional reversal solution. They chose Sentient Science because while it does not account for shock loading that would emphasize WindTC significantly more, it provides a very conservative approach to the life factor analysis for the WindTC application.
Together, the teams decided to evaluate the life of a 1.5MW high speed bearing under a real-world representative duty cycle to calculate the bearing life. These bearings have experienced high rates of white etch inclusions in the field.
Aerotorque provided their data on the hard stop amplitude and frequency and Sentient studied and modeling the white etch-like inclusions and made a representative material model. Sentient’s modeling approach was chosen because traditional tools cannot accurately calculate bearing life because they don’t account for material quality and inclusions, material microstructure, surface finish, or lubricant.
Recent validations in the marketplace have made Sentient the leading provider of predictive maintenance and decision support solutions for some of the largest wind operators in North America. Today, over 13% of the operating wind assets in the US are under Sentient Science management. Sentient’s customers now control over 40% of the US wind fleet.
When the models were complete, Sentient ran the simulations through their DigitalClone® life prediction tool to assess the life of the high speed bearing with new duty cycles and with inclusions added.
The DigitalClone® simulations showed that Aerotorque WindTC reduced overload and torque events in the drivetrain and reduce stresses on components by factor of 4. It also showed white etch area (WEA) reduced bearing L50 life based on rolling contact fatigue by 46%. If WEA can be prevented using Torque Control (TC), designed to reduce the magnitude and speed of impact and reversal loads, then bearing L50 life can be extended by up to 2x. Damage propagation in WEA is mostly controlled at nominal Power Output. However, Torque Control can help if many Hard Stops (HS) occur in a turbinelife. The teams are continuing to further examine the a affects of dynamic loads and impact loads, which were not considered in this program.