Wind turbine gears

Many sections of the wind turbines include gears. For the pitch regulation a drive pulls inside on an internal toothed rim, and to rotate the wind turbine against the wind so-called YAW-drives are used, where a number of drives are pulling on a large toothed rim which is fixed on the tower. The latter can be with either internal or external toothing.

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Due to the slow speed all the above gears are typically of a coarse quality. The gears are generally finished by hobbing and case hardened. During recent years, more and more manufacturers have however used ground teeth on the drives in order to obtain a better distribution of the surface pressures. Here, extremely large flank line modifications and tip reliefs are being used to compensate for deflection and non-parallelism.

The precision gears are located in the generator gear. We are talking about gear ratios of altogether up to over 1:100 and large torques which are being transmitted. In the new versions we are talking about up to three planetary gear stages and subsequent one or two normal gear stages.

Hero Gears A/S can provide the ground YAW-drives and some of the generator gears according to shape and size. Special for planetary gears is that they must not be magnetic as the gear will then run as a generator and produce power.

Generally, complete documentation is required for wind turbine gears such as:

• Material certificate.
• Heat treatment certificate.
• 3D geometry measurement.
• Gear measurement report.
• Crack inspection report.
• Magnetism measurement of planetary gears.
• Surface hardness measurement of teeth after grinding.
• Grind burning test according to Backhausen and/or acid burning test.