Brakes provide emergency control for wind turbines
Warner Electric's new modified ERS series of spring-engaged, electrically-released, brakes is helping to further the growth of wind energy by providing the crucial braking function for large wind turbines under maximum wind conditions. The modified ERS series of electromagnetic brakes provides an optimum solution to safeguard the ongoing major investments in large wind turbines that are the direct result of the booming global demand for wind power, expected to reach 50,000MW by 2020.
The brakes operate as pitch brakes in wind turbine applications that require both "static" holding power, and the ability to withstand high inertia dynamic stopping in emergency situations. They are mounted outboard of an inductive encoder which is fitted to the back of a motor to position the blades to the correct pitch. In addition to their braking efficiency, the ERS series units also offer the advantage of being a one-piece design, which is fully enclosed and painted to withstand extreme environmental conditions (salt-spray, condensation, water, etc). Previous to this design, pitch brake models have tended to be more complex two-piece units that require an adapter plate, extra fasteners and an external boot-type seal in the gap between the brake and the adapter plate to prevent contamination.
In normal operation, the ERS brakes function as a static brake to hold the blades from rotating in a power-off situation, during routine maintenance, or for inspection purposes. However, the design spec already produced for one major manufacturer requires the brake to also be able to make 1,000 fully loaded dynamic stops during its service life. The largest in the Warner Electric ERS series, the ERS68 brake for example offers 100 ft lbs of static torque with a maximum of 2,000 rpm and a brake release time of 0.2 sec. The ERS68 weighs in at only 5kg and has been tested to a capacity of more than 20,000 fully loaded dynamic stops, surpassing the design spec by a factor of 20.
Static holding brakes
Warner Electric has also developed a series of static holding brakes as part of its comprehensive package for wind turbines. The static brakes meet the strict design criteria for controlling yaw when the wind turbine nacel is positioned into the wind. For this technically simpler application, the yaw brakes are also mounted on the back end of a motor. Typically three pitch brakes and four to five yaw brakes are installed for motion control in the nacelle of each wind turbine.
Solutions for other smaller wind turbine applications have also been solved using Warner Electric brakes, these include the Vertical Axis Wind Turbine and the Wind Wall, an urban wind turbine designed to be sited on roofs or on the sides of buildings in windy city areas.
Warner Electric Ltd
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