Wind Turbine Yaw System: Mechanical Parts
The primary mechanical parts of the Yaw System are
- motors and gearboxes: which provide the power to turn the nacelle,
- yaw bearing: a low friction wear surface which the nacelle slides on as it turns,
- yaw ring or bull gear: a gear that is fixed to the tower, and
- yaw brake: assemblies that secure the main frame of the nacelle to the yaw ring and hold the nacelle in a fixed position when needed.
This section provides information about the relationship of the yaw bearing, yaw ring, and brakes.
Yaw rings
The yaw ring is a large gear that engages the pinion gears of the yaw motor gearboxes. Because these gears carry high loads, proper lubrication is important to prevent excessive wear.
Yaw rings may be made in sections or sectors which allow the replacement of only the worn portion or the ring when wear limits are reached.
The yaw ring attaches to the tower by means of a bolted joint.
This joint is critical. It’s important to properly torque these bolts to ensure proper bolt preload since the failure of this joint during operation would be catastrophic.
Yaw Bearings
The yaw bearings may be plain bearings as shown here, roller or ball bearings. The yaw bearings control both radial and axial motion. The plain bearings shown are made of a thermal plastic polymer that has good sliding properties but is strong enough to support the weight of the nacelle and handle the loads imposed when the brakes are clamped tight.
Yaw Brakes
The yaw brakes are similar to the disc brakes found on a car. A caliper uses hydraulic pressure to squeeze friction pads against the rotating disc. In this case, the disc is the yaw ring itself. Pressure holds the pads tight against the ring, locking the nacelle in position.
The two halves of the caliper bolt together limiting axial motion, but allowing the nacelle to rotate when the brakes are released.
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