Why gears fail and a few ideas for building better replacements
Wind turbine gearboxes connect a relatively low-speed rotor to a high-speed generator. Synchronous generators must run at synchronous speed, while induction generators run slightly above that (e.g. 105% of synchronous speed but that depends on load). For 60-Hz power, synchronous speed is found by dividing 3,600 by half the number of electrical poles in the generator. Synchronous speeds can be 3,600, 1,800, 1,200 rpm and so on. Rotor speed depends upon its diameter, typically 10 to 20 rpm. This combination requires a large speed-up ratio. Gear boxes for 60-cycle power with large speed-up ratios are complex in design and require epicyclic (planetary) gear sets. Planetary gear boxes have multiple meshes, speeds, and a complex power flow.A varying wind speed and turbulence place loads on the input shaft in addition to the torque that all prime movers exert. The blades are long compared to the length of input shaft. In addition, they operate in the boundary layer so wind speed is higher at the top of the rotor sweep compared to the bottom. And then each blade tip generates a vortex which increases turbulence for downwind units.
