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Moog Obtains TÜV Rheinland Certification for Safety-Critical Blade Feathering on Wind Turbines

Pitch Servo Drive ensures functional safety of the turbines

18 September 2012

The Moog Pitch Servo Drive, a key product in Moog’s Pitch Systems that is responsible for guaranteeing the safe operation of wind turbines, has obtained TÜV certification for compliance with the guideline for the certification of wind turbines GL2010 issued by Germanischer Lloyd. This validates that Moog designs achieve Performance Level D for the feathering safety function, which ensures that the most critical operation of utility scale turbines meets relevant global standards. Moog leveraged its technical leadership and extensive experience in this field to be one of the first companies to obtain this certification for AC Electric Pitch Systems.

The safety of wind turbines is governed by a number of competing standards and requirements including the ISO 13849-1 standard, which is referenced as a suitable functional safety standard in the GL2010 guideline. This guideline recommends Performance Level D as an appropriate safety level for feathering of a turbine. The feathering safety function alters the blade pitch at the rotor hub to minimize the torque applied by the wind, thereby avoiding possible excessive speed of the turbine.

Until now, no safety functions conforming to ISO 13849-1 have been implemented in wind turbines for AC pitch systems. This is partly because conformance may require significant changes to turbine components and systems. “The lack of clarity on the requirements is a big challenge for components suppliers and turbine manufacturers as well as for the certification bodies in the design and approval process of new wind turbines,” says Matthias Pauli, core components manager at Moog in Unna, Germany.

The Pitch Servo Drive is a key component in electric pitch systems that is responsible for controlling the blade angle during turbine operation and for the feathering safety function. As a result the pitch servo drive is classified as a safety critical component. The mechanical sizing and load calculations of three-bladed wind turbines are such that it is sufficient for two of the three blades to move to the feathering position.

The TÜV Rheinland certificate qualifies the Moog Pitch Servo Drives (Pitchmaster II and Pitchmaster II+ models) as providing the necessary robust hardware and software for Performance Level D for the feathering safety function in a two out of three redundancy configuration.