Turbines of the year: Drivetrains

WORLDWIDE: The specialist manufacturers and OEMs look for weight reduction and more compact dimensions with their latest designs.

Enercon EP4 Electrically excited air-cooled ring generator is constructed in sections

GOLD Enercon EP4 Modular direct-drive fenerator

Enercon introduced its first super-size ring generator in 2002 for the 4.5MW E-112 model, with a current rating of 7.6MW for the 12-metre diameter electric machine — which has since sold around 85 units. The new electrically excited and air-cooled ring generator for the 4.2MW E-126 is, by comparison, much more compact, with an outer diameter of 7.5-8 metres. These dimensions also positively impact matching nacelle mass, diameter and length.

The electric machine itself consists of four 180-degree segments (two stator and two rotor), and these are transported in 180-degree stator plus rotor sub-assemblies. A main benefit of splitting the generator is a significant improvement in train transportation and road-transport logistics. The generator halves are assembled on site.

Enercon retained its standard 400V generator voltage, but a new stator coil design offers enhanced heat dissipation capability. The larger specific generator volume further enhances natural heat dissipation, whereas the combination with a new stator coil design enables air cooling.

This results in a 35% reduction in cooling-system energy consumption, while the use of cooling fans necessary for additional generator temperature management could be reduced by half, the company claims.