Page 202 - Fluid Power Engineering

174 Chapter Nine

FIGURE 9-3 Schematic of the components of a wind turbine. 1. Pitch drives of
two types—motor and hydraulics. 2. Rotor that connects blades to main
shaft. 3. Main shaft. 4. Main bearing. 5. Gearbox. 6. Yaw drive. 7. Disk
brakes. 8. Brake hydraulic system. 9. Generator. 10. Main hydraulic system.
11. Nacelle frame. 12. Yaw brakes. (With permission from Bosch Rexroth,
maker of gearbox, pitch drive, yaw drive, and hydraulic system.)

and tempered steel and it rests on the main bearing labeled 4. The
main bearing rests on the nacelle frame (labeled 11). The main shaft
connects the hub to the gearbox (labeled 5). The rotational torque is
transferred from the hub to the main shaft, which transfers the torque
to the gearbox. The bearing transfers all three components of force on
the rotor hub—parallel to axis of tower, parallel to axis of rotation,
and transverse force—to the bearing, which transfers to the nacelle
frame. The nacelle frame (labeled 11), rests on the tower and transfers
all the forces to the tower. The yaw drive (labeled 6), rotates the nacelle
along the vertical axis. The gearbox is connected to generator (labeled
9). The shaft connecting the two has disk brake (labeled 7). The brake
hydraulic system (labeled 8), controls the brakes.
An alternative configuration for a turbine with gearbox is to di-
rectly connect the rotor hub and gearbox. This is seen in Fig. 9-4. Here,
a double roller-tapered bearing is integrated with rotor hub and na-
celle frame, thereby eliminating main shaft to carry power from rotor
to gearbox. The outer ring of the bearing is connected to the nacelle
frame and the inner ring is connected to a short rotor shaft. It elim-
inates the need for two bearings. This configuration makes the na-
celle compact and reduces the overall weight of the turbine. However,
maintenance of gearbox may be challenging.
In direct drive turbines, there is no gearbox and the hub is di-
rectly connected to a variable speed generator (see Fig. 9-5). In such a