WTT Mechanical Systems 3 — Questions and Answers
Question 1: Which component converts rotor torque to a higher speed, lower torque output for the generator?
- Pitch actuator
- Gearbox (Correct answer)
- Transformer
- Power converter
Correct answer: Gearbox
The gearbox increases rotational speed from the slow rotor to the generator's required speed, trading torque for RPM.
Question 2: What is the purpose of the blade pitch bearings in a variable-pitch wind turbine?
- Allow blades to rotate about their longitudinal axis to control aerodynamic angle of attack (Correct answer)
- Support the rotor weight against the main shaft
- Provide a pivot point for yaw rotation
- Connect blade sections during transport
Correct answer: Allow blades to rotate about their longitudinal axis to control aerodynamic angle of attack
Pitch bearings are large slewing rings that allow each blade to rotate around its own longitudinal axis, enabling pitch angle control for power and speed regulation.
Question 3: When inspecting a high-speed shaft coupling, which defect is most critical to address immediately?
- Minor surface rust on the flange face
- Cracked or missing elastomeric coupling elements (Correct answer)
- Paint scuffing on the guard
- Slight discoloration of the coupling guard
Correct answer: Cracked or missing elastomeric coupling elements
Cracked or missing elastomeric elements in a coupling compromise torque transmission and misalignment compensation, risking catastrophic drivetrain failure.
Question 4: What maintenance action is performed when a technician 'tightens to torque spec' on a bolt?
- Applies lubricant to prevent galling
- Uses a calibrated torque wrench to reach the manufacturer's specified clamping force (Correct answer)
- Installs a new bolt with thread-locking compound
- Verifies bolt grade markings before installation
Correct answer: Uses a calibrated torque wrench to reach the manufacturer's specified clamping force
Torquing to spec means using a calibrated torque wrench to apply precisely the clamping force specified by the manufacturer, ensuring proper joint integrity.
Question 5: In a three-stage helical planetary gearbox, which stage typically experiences the highest torque?
- High-speed output stage
- Intermediate stage
- Low-speed input (planetary) stage (Correct answer)
- All stages experience equal torque
Correct answer: Low-speed input (planetary) stage
The input stage closest to the rotor carries the highest torque because torque is highest at low rotor speed and decreases as speed increases through the stages.
Question 6: What does the term 'backlash' refer to in a wind turbine gearbox?
- Oil foaming during high-speed operation
- The small clearance between mating gear teeth flanks (Correct answer)
- Reverse torsional loading on the main shaft
- Gear tooth pitting propagation
Correct answer: The small clearance between mating gear teeth flanks
Backlash is the intentional clearance between mating gear tooth flanks that allows thermal expansion and lubrication film formation.
Question 7: Which condition is indicated when a vibration analysis shows a dominant frequency at 1× shaft RPM?
- Gear mesh frequency fault
- Mass imbalance on the rotating component (Correct answer)
- Bearing outer race defect
- Electrical frequency interference
Correct answer: Mass imbalance on the rotating component
A dominant vibration component at 1× (once per revolution) is the classic signature of mass imbalance on a rotating shaft or rotor.
WTT Mechanical Systems 3
Which component converts rotor torque to a higher speed, lower torque output for the generator?