This avoids the high loads that would be generated in the wind turbine as a result of the unsynchronized pitch speeds typical of the usual approaches.
The new integrated permanent magnet synchronous motor (IPMSM) has been specially designed for pitch applications. It ensures maximum efficiency at low speeds during pitch operation and a maximum torque capacity of up to 3.5 times the pitch's nominal torque, even in the event of a power failure. The motion control concept guarantees a wide field weakening operating area, allowing for complete control of the flag position speed, even in the event of a power outage.
To ensure that all applications meet the performance requirements set out in IEC 61400 and GL 2010 standards, Moog has developed a standardized performance qualification process for pitch actuators.
A wind turbine pitch control system must fulfill two essential functions: first, it must act as an actuator for power and speed control when the wind exceeds the turbine's predetermined limits; second, it must act as the actuator for the turbine's braking system.
To stop the turbine, all three blades must be feathered, and to distribute and balance the loads on all structural components during this process, the three pitch axes must move out of the wind in a synchronized manner.
Several open-loop control schemes already exist for flagging the pitch actuator if the pitch shaft position feedback signal is lost: hydraulic actuators, DC motor pitch actuators, and AC induction pitch actuators. However, all three systems share the same drawback: the speed of each shaft is highly dependent on the load applied to the blade. Moog's new control scheme overcomes this limitation.
Compared to the usual self-sensing control schemes for AC synchronous or induction motors, the new closed-loop speed control scheme provides up to three times the rated torque from the stall point to ensure safe, high-performance movement to the flag position.
