New bearing solutions for wind turbine rotors and gears

Wind turbine manufacturers and operators are currently faced with enormous challenges. But Schaeffler says it can ensure higher performance on a permanent basis within exactly the same installation space, while simultaneously extending the lifetimes of existing wind farms, improving the carbon footprint, and ultimately reducing electricity generation costs.

Increasing power density in wind turbine gears, combined with the demand for reduced weight and cost, requires new bearings concepts. With planetary gears, this leads to a larger number of planets with smaller diameters, known as ‘multi-planet concepts.’ This means that not enough space is available for rolling bearings in the planet gears.

Hydro-dynamic plain bearings are the solution here because of their low cross-section. At WindEnergy Hamburg, Schaeffler is introducing its new hydro-dynamic plain bearings and related engineering for planet gears. This is because a thorough understanding of the systems and new simulation and calculation methods, as well as the corresponding tools, is required to ensure that the bearings function smoothly.

Schaeffler also notes that performance optimisation has brought about a marked trend towards adjusted bearings with two tapered roller bearings in an O arrangement. The increased support spacing of this bearing arrangement reduces the inner bearing loads, whereby the bearing can be made smaller and lighter. To ensure that the adjusted bearings continue to function year on year, Schaeffler engineers fall back on various options from the tapered roller bearing construction kit.

Selection takes place as part of a multi-level system simulation, which takes into account the effect of forces and deformation on the bearings in operation. The bearing details are checked, and in a simulation, the correct pre-load – essential for the adjusted bearings – is determined. In order to ensure this, both during the installation process and in operation, Schaeffler offers the PREMESY pre-load measuring system.

Also on show will be split asymmetric spherical roller bearings. Worldwide, a large proportion of the drive train concepts installed on rotors are fitted with spherical roller bearings. If these bearings fail prematurely, the high replacement cost usually renders it uneconomical to replace them. For such cases, Schaeffler has developed a robust solution based on split asymmetric spherical roller bearings. The company says this solution can reduce the cost of replacing the bearings by a good 50 per cent.

Since the entire replacement process takes place in the nacelle, it is not necessary to disassemble the rotor star or powertrain. All the necessary components are lifted into the nacelle using the deck crane and assembled in situ. Therefore, Schaeffler enables operators to continue to operate existing wind turbines cost-effectively.