Saptarshi Sarkar

and 2 more

Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their Rolling Contact Fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well known that these premature failures are attributed to different types of surface damage. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied. Then, a novel idea of open-loop high-speed shaft mechanical brake control is proposed. The results show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high-speed shaft and reducing the risk of bearing slip. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time.