WTT Wind Turbine Components & Design 3 — Questions and Answers
Question 1: What is the primary role of the yaw system in a horizontal-axis wind turbine?
- To rotate the nacelle so the rotor faces into the wind (Correct answer)
- To tilt the blades upward during high-wind events
- To slow rotor speed when power demand drops
- To align the tower with prevailing soil loads
Correct answer: To rotate the nacelle so the rotor faces into the wind
The yaw system continuously rotates the nacelle about the vertical tower axis to keep the rotor aligned with the wind direction for maximum energy capture.
Question 2: In a doubly fed induction generator (DFIG) wind turbine, power is fed to the grid from:
- Both the stator and rotor windings simultaneously (Correct answer)
- Only the stator winding
- Only the rotor winding via slip rings
- A separate DC bus connected to a battery bank
Correct answer: Both the stator and rotor windings simultaneously
DFIG turbines inject power into the grid from both the stator directly and the rotor through back-to-back power converters, enabling variable-speed operation.
Question 3: Which bearing type is commonly used at the main shaft of a wind turbine to handle combined radial and axial (thrust) loads?
- Spherical roller bearing or tapered roller bearing (Correct answer)
- Deep-groove ball bearing only
- Needle roller bearing only
- Plain sleeve bushing
Correct answer: Spherical roller bearing or tapered roller bearing
Spherical or tapered roller bearings are used at the main shaft because they can carry the large combined radial loads from rotor weight and axial thrust from wind pressure.
Question 4: What is the purpose of a wind turbine's transformer located at the base of the tower?
- To step up generator voltage to grid transmission voltage (Correct answer)
- To convert AC power to DC for battery storage
- To regulate blade pitch servo pressure
- To filter harmonics from the yaw drive motor
Correct answer: To step up generator voltage to grid transmission voltage
The pad-mount or tower-base transformer steps up the low generator voltage (typically 690 V) to medium-voltage grid level (e.g., 34.5 kV) for efficient transmission.
Question 5: What distinguishes an upwind turbine design from a downwind design?
- The rotor faces into the wind on an upwind turbine, while the rotor is on the lee side on a downwind turbine (Correct answer)
- An upwind turbine has blades below the hub; a downwind turbine has blades above
- An upwind turbine uses variable pitch; a downwind turbine uses fixed pitch
- An upwind turbine has a horizontal axis; a downwind turbine has a vertical axis
Correct answer: The rotor faces into the wind on an upwind turbine, while the rotor is on the lee side on a downwind turbine
Upwind turbines position the rotor facing the oncoming wind, preventing tower shadow effects, while downwind turbines place the rotor behind the tower, which can cause blade fatigue from tower wake.
Question 6: Which component in the nacelle is responsible for converting mechanical rotation into electrical energy?
- Generator (Correct answer)
- Gearbox
- Main shaft
- Power converter
Correct answer: Generator
The generator converts the mechanical rotational energy from the drivetrain into electrical energy through electromagnetic induction.
Question 7: What is the function of the mechanical brake (rotor lock) on a wind turbine during maintenance?
- To lock the rotor stationary so technicians can safely work on the drivetrain (Correct answer)
- To limit rotor speed to rated RPM during power generation
- To stop the rotor in emergency braking scenarios instead of pitch
- To engage only when grid power is lost
Correct answer: To lock the rotor stationary so technicians can safely work on the drivetrain
The rotor lock (parking brake) mechanically clamps the main shaft or high-speed shaft to prevent any rotation while technicians perform maintenance inside the nacelle.
WTT Wind Turbine Components & Design 3
What is the primary role of the yaw system in a horizontal-axis wind turbine?