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This content will become publicly available on November 10, 2018

Title: Investigation of high-speed shaft bearing loads in wind turbine gearboxes through dynamometer testing

Many wind turbine gearboxes require repair or replacement well before reaching the end of their design life. The most common failure is bearing axial cracks, commonly called white etching cracks (WECs), which typically occur in the inner raceways of the high-speed parallel-stage rolling element bearings. Although the root causes of WECs are debated, one theory is that they are related to routine dynamic operating conditions and occasional transient events prevalent in wind turbines that can result in high bearing stress and sliding of the rolling elements. Here, this paper examined wind turbine gearbox high-speed shaft bearing loads and stresses through modeling and full-scale dynamometer testing. Bearing outer race loads were directly measured and predicted using a variety of modeling tools in normal operations, misaligned conditions, and transient events particularly prone to bearing sliding. Test data and models of bearing loads were well correlated. Neither operational misalignment due to rotor moments nor static generator misalignment affected the bearing loads when compared with pure-torque conditions. Thus, it is not likely that generator misalignment is a causal factor of WECs. In contrast, during transient events, the bearings experienced alternating periods of high stress, torque reversals, and loads under the minimum requisite at highmore » rotating speeds while showing indications of sliding, all of which could be related to the formation of WECs.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Wind Technology Center
Publication Date:
Report Number(s):
NREL/JA-5000-66889
Journal ID: ISSN 1095-4244
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Wind Energy
Additional Journal Information:
Journal Volume: 21; Journal Issue: 2; Journal ID: ISSN 1095-4244
Publisher:
Wiley
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Wind and Water Technologies Office (EE-4W)
Country of Publication:
United States
Language:
English
Subject:
17 WIND ENERGY; axial crack; bearing load; gearbox; reliability; white etching crack
OSTI Identifier:
1409495