WTT Mechanical Systems 2 — Questions and Answers
Question 1: What is the purpose of a yaw brake in a wind turbine?
- To stop rotor rotation during emergencies
- To hold the nacelle in position against wind loads after yawing (Correct answer)
- To regulate generator speed
- To apply friction to the main shaft
Correct answer: To hold the nacelle in position against wind loads after yawing
The yaw brake locks the nacelle in the desired wind-facing orientation, preventing unwanted rotation from lateral wind forces.
Question 2: Which bearing type is most commonly used for the main shaft (low-speed shaft) in a wind turbine?
- Deep groove ball bearing
- Tapered roller bearing
- Spherical roller bearing (Correct answer)
- Needle roller bearing
Correct answer: Spherical roller bearing
Spherical roller bearings accommodate shaft misalignment and handle both radial and axial loads, making them ideal for the main shaft.
Question 3: What does a negative pressure inside the nacelle typically indicate?
- Cooling fans are offline
- There is a proper pressure differential preventing moisture ingress (Correct answer)
- A structural seal has failed
- The gearbox is overheating
Correct answer: There is a proper pressure differential preventing moisture ingress
Slight negative (below ambient) pressure inside the nacelle ensures that airflow moves inward rather than outward, reducing moisture and contamination ingress.
Question 4: During a rotor lock procedure, the rotor lock pin engages with the:
- Yaw ring
- Hub flange
- Rotor lock disk on the main shaft or gearbox (Correct answer)
- Blade pitch ring gear
Correct answer: Rotor lock disk on the main shaft or gearbox
The rotor lock pin inserts into holes on a dedicated lock disk attached to the main shaft or gearbox input, mechanically preventing rotation.
Question 5: What is the primary function of flexible couplings between the gearbox output and the generator?
- Increase torque multiplication
- Compensate for minor shaft misalignment and dampen torsional vibrations (Correct answer)
- Provide an emergency disconnect
- Step up rotational speed
Correct answer: Compensate for minor shaft misalignment and dampen torsional vibrations
Flexible couplings absorb misalignment and vibration between the gearbox output shaft and generator input, protecting both components.
Question 6: A wind turbine gearbox oil sample shows elevated copper levels. This most likely indicates wear of:
- Steel planetary gears
- Bronze or brass bushings and thrust washers (Correct answer)
- Hardened bearing races
- Carbon fiber composite housings
Correct answer: Bronze or brass bushings and thrust washers
Elevated copper in oil analysis typically indicates wear of bronze or brass bushings, thrust washers, or bearing cages inside the gearbox.
Question 7: What is the typical consequence of operating a wind turbine with excessive rotor imbalance?
- Increased power output
- Accelerated bearing wear and structural fatigue (Correct answer)
- Reduced yaw motor demand
- Higher gearbox oil temperature
Correct answer: Accelerated bearing wear and structural fatigue
Rotor imbalance creates cyclic loads that accelerate bearing wear, cause structural fatigue in the tower and main frame, and increase vibration throughout the drivetrain.
WTT Mechanical Systems 2
What is the purpose of a yaw brake in a wind turbine?