Abstract

Accurate knowledge of the input torque in wind turbine gearboxes is key to improving their reliability. Traditionally, rotor torque is measured using strain gauges bonded to the shaft. Transferring the resulting signal from the rotating shaft to a stationary data acquisition system while powering the sensing devices is complex and costly. The magnitude of the torques involved in wind turbine gearboxes and the high stiffness of the input shaft pose additional difficulties. This paper presents a new alternative method to measure the input torque in wind turbine gearboxes based on deformation measurements of the static first stage ring gear. We have measured deformation using fiber optic strain sensors based on fiber Bragg gratings because of their advantages compared to conventional electrical strain gauges. The present study was conducted on a Siemens Gamesa Renewable Energy gearbox with a rated power of 6MW, in which a total of 54 fiber optic strain sensors were installed on the outer surface of the first stage ring gear. The gear mesh forces between the planets and the ring gear cause measurable deformations on the outer surface of the stationary ring gear. The measured strains exhibit a dynamic behavior. The strain values change depending on the relative position of the strain sensors to the planet gears, the instantaneous variations of the input torque, and the way load is shared between planets. A satisfactory correlation has been found between the strain signals measured on the static ring gear and torque. Two signal processing strategies are presented in this paper. The first procedure is based on the peak-to-peak strain values computed for the gear mesh events, and therefore, torque can only be estimated when a gear mesh event is detected. The second signal processing procedure combines the strain signals from different sensors using a Coleman coordinate transformation and tracks the magnitude of the fifth harmonic component. With this second procedure, it is possible to estimate torque whenever strain data of all sensors is available, leading to an improved frequency resolution up to the sampling frequency used to acquire strain data. The method presented in this paper could make measuring gearbox torque more cost-effective, which would facilitate its adoption in serial wind turbines and enable novel data-driven control strategies, as well as a more accurate assessment of the consumed fatigue life of the gearboxes throughout their operation.

Highlights

  • Scientists have long been warning us that we face a significant challenge regarding our climate

  • The main contributions of this paper are, 1) to develop a new method to measure input torque in wind turbine gearboxes based on deformations in the fixed frame, and overcoming all the difficulties related to measuring on a rotating shaft, 65 2) the use of fiber optic strain sensors to explore their advantages compared to conventional electric strain gauges, 3) open the way to investigate the load sharing between planets, and 4) experimental demonstration of the above on a full-scale wind turbine gearbox

  • The torque signals were averaged for the time segments between the tensile and compression peaks. 3.2 Relationship between peak-to-peak strain values and torque Having measured strain on 54 locations on the outer surface of the static first stage ring gear, and with the simultaneous data 205 available from the torque transducers installed at both high-speed shafts, the following subsection shows how the measured strain signals can be correlated with the input torque

Read more

Summary

Introduction

Scientists have long been warning us that we face a significant challenge regarding our climate. Current wind turbine design codes lack insight into the dynamic behavior of the internal drive train components It is, highly desirable to be able to measure the torque from the rotor acting on the gearbox accurately and reliably. The main contributions of this paper are, 1) to develop a new method to measure input torque in wind turbine gearboxes based on deformations in the fixed frame, and overcoming all the difficulties related to measuring on a rotating shaft, 65 2) the use of fiber optic strain sensors to explore their advantages compared to conventional electric strain gauges, 3) open the way to investigate the load sharing between planets, and 4) experimental demonstration of the above on a full-scale wind turbine gearbox.

Background
Test bench set-up
Fiber optical sensors
Experiments
Signal processing
Torque estimation using peak-to-peak strain values
Torque estimation procedure using peak-to-peak strain values
Torque estimation using a coordinate transformation
Torque estimation procedure with a coordinate transformation
Discussion
Findings
Conclusions

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.