Figure 15 Permanent magnet generator, courtesy of Indar.
Function
The generator converts mechanical energy to electrical energy.
What it costs*
The generator cost varies significantly for different nacelle layouts.
Who supplies them
Suppliers include ABB, Elin, GE, GreenSpur, Ingeteam, Leroy Somer, P.P.I Engineering and VEM.
Key facts
Most generators use permanent magnets that need no excitation power. This keeps mass low and dimensions small, lowering transport and installation costs, but does rely on the use of alloys of rare-earth elements.
All operate at variable speed, with grid connection via a AC-DC-AC converter. This enables the smoothing of drive train loading and the optimisation of aerodynamic performance without the need for a variable ratio gearbox.
Efficiency is critical, especially at part load, as a wind turbine spends many hours generating 20% to 80% of rated power in low-to-medium wind speeds.
Water-cooling is common in order to maximise efficiency and compactness whilst limiting noise levels.
Generator bearings are designed to avoid passage of electrical current and with special emphasis on lubrication. Typically, these are specialist deep-groove bearings, sometimes with ceramic rolling elements.
Related, but not part of the scope of supply of the generator, is the coupling that connects the generator to the gearbox. As both components are flexibly mounted and the wind turbine structure is relatively flexible compared to the loading applied, such couplings generally are able to cope with substantial misalignment.
What’s in it
- Castings
- Windings
- Bearings
- Sensors
- High-speed shaft coupling