Standard for Design and Specifications of Gearboxes for Wind Turbines

ANSI/AGMA 6006-B20

ANSI/AGMA 6006-B20


This standard is applicable to enclosed speed increasing gearboxes for horizontal axis wind turbine drivetrains with a power rating in excess of 500 kW. This applies to wind turbines installed both onshore and offshore. This standard applies to modular and integrated designs.

The standard provides guidance on the application of the wind turbine loads in relationship to the design of gears and gearbox elements. A standardized method for calculating gearbox reliability is included which allows for an objective comparison of different gearbox designs. Furthermore, this method provides a means to evaluate designs based upon gearbox lifetime economics.

The gearing elements referenced include spur, helical or double helical and their combinations in parallel and epicyclic arrangements in the main power path.

The standard applies to designs using rolling element bearings. Plain bearings are permissible, although their use and rating is not covered.

Guidance is included on the specification of shafts, shaft interfaces and fits, bearings and gear housing structure.

Lubrication of the gearbox is covered along with prototype and production testing.


This standard is intended to apply to wind turbine gearboxes. It provides information for specifying, selecting, designing, manufacturing, testing, procuring, operating and maintaining reliable speed increasing gearboxes for wind turbine generator system service.

Annex information is supplied on wind turbine architecture, wind turbine load description, quality assurance, operation and maintenance, minimum purchaser gearbox manufacturer ordering data, lubrication selection and monitoring, determination of an application factor from a load spectrum using the equivalent torque, and bearing stress calculations.


[The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of ANSI/AGMA 6006-B20, Standard for Design and Specification of Gearboxes for Wind Turbines.]

The operation and loading of a wind turbine speed increasing gearbox is unlike most other gear applications. The intent of this standard is to describe the differences. Much of the information is based on field experience. This standard is a tool whereby wind turbine and gearbox manufacturers can communicate and understand each other’s needs in developing a gearbox specification for wind turbine applications. The annexes present informative discussion of various issues specific to wind turbine applications and gear design.

A combined committee of AWEA and AGMA members representing wind turbine manufacturers, operators, researchers, consultants, and gear, bearing and lubricant manufacturers were responsible for the drafting and development of this standard.

The committee first met in 1993 to develop AGMA/AWEA 921-A97, Recommended Practices for Design and Specification of Gearboxes for Wind Turbine Generator Systems. The AGMA Information Sheet was approved by the AGMA/AWEA Wind Turbine Gear Committee on October 25, 1996 and by the AGMA Technical Division Executive Committee on October 28, 1996. This standard supersedes AGMA/AWEA 921-A97.

The first draft of ANSI/AGMA/AWEA 6006-A03 was made in March 2000. It was approved by the AGMA membership in October 2003. It was approved as an American National Standard on January 9, 2004.

In 2005, ANSI/AGMA/AWEA 6006-A03 was adopted internationally as International Standards Organization (ISO) 81400-4, Wind Turbines – Part 4: Design and Specification of Gearboxes.

The International Electrotechnical Commission (IEC) published IEC 61400-4 in 2012, updating the initial work established in ANSI/AGMA/AWEA 6006-A03.

ANSI/AGMA 6006-B20 is a revision of ANSI/AGMA/AWEA 6006-A03. This edition continues the development from the previous standards to provide concise requirements for gearbox design and specifications as well as introducing a reliability calculation method.

The first draft of ANSI/AGMA 6006-B20 was created in July 2016. It was approved by the AGMA membership in August 2, 2019. It was approved as an American National Standard on February 11, 2020.

Pages: 46

ISBN: 978-1-64353-073-4

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