Brakes for pitch and yaw
December 15, 2010 by Paul Dvorak
Filed under Wind Power News, Yaw and Pitch Brakes
Six Intorq brakes.
The requirements for pitch and yaw brakes include high reliability, long maintenance cycles, resistance to environmental influences, and a tight braking-torque tolerance. For pitch drives, one brake manufacturer has developed spring loaded devices as holding brakes that have to perform in a particular way in emergencies, even after a failure. The brake casing is encapsulated. Yaw drives use brakes from the company’s modular BFK458 series. In the event of a fault, the brakes act as a friction clutch to let the nacelle move with the wind. Offshore duty calls for high corrosion protection and durability. Encapsulated versions with special surface protection are used there.
Example applications also include spring-applied brakes in pitch drives.
A bridge/half-wave rectifier has proven useful. After a period, the bridge/half-wave rectifiers switch over from bridge rectification to half-wave rectification. Depending on design, over-excitation or holding current reduction or both, it is possible to shorten the switching times or reduce self-heating (power reduction).
Company engineers have modified the insulation for this area of use and stored-spring brakes without partial discharge can be supplied as an option. The advantages of over-excitation and reduction of the holding current can be combined with each other in this case.
The image provides some explanation as to how the bridge/half-wave rectification functions and how reducing the holding voltage and over-excitation behaves when selecting a suitable coil voltage. When stored-spring brakes are operated from the DC link of a frequency inverter with pulse width modulation, partial discharge can occur and damage the coil system.
Intorq US Inc.
Brakes for pitch and yaw drives
June 11, 2009 by Paul Dvorak
Filed under Electrical Systems, Yaw and Pitch Brakes
Emergency braking requirements of today’s large wind turbines under maximum wind conditions are comparable to those of a 40-ton mining truck driving down a 25% grade at 87 mph with a cliff just ahead. To meet these demanding requirements, Warner Electric
Warner Electric’s ERS68 pitch and yaw brakes provide emergency stopping power and improved protection from harsh environmental conditions.
, South Beloit, Wisc., an Altra Industrial Motion company, modified its ERS series of electrically-released, spring-engaged brakes to serve as pitch brakes for wind turbine applications that require both “static” holding power and to withstand high inertia dynamic stops in an emergency situation.
The electromagnetic brake mounts outboard of an inductive encoder which is mounted to the back of a motor to position the blades to the proper pitch. In normal use, the unit functions as a static brake to hold the blades from rotating in a power-off situation, during routine maintenance and for other reasons.
However, the design spec for one OEM requires the brake to make 1,000 fully loaded dynamic stops during its service life. The largest in the Warner Electric ERS series, the 11.3-pound ERS68, has been tested to a capacity of more than 20,000 fully-loaded dynamic stops, surpassing the design spec 20 fold. The ERS68 brake offers 100 ft. lbs. of static torque, a maximum of 2,000 rpm, and a brake release time of 0.2 sec.
The new blade-pitch brakes also have the advantage of being a one-piece design, fully-enclosed and painted to withstand extreme environmental conditions such as salt-spray, condensation, and water. Previous pitch brakes used two-piece designs that required an adapter plate, extra fasteners, and an external boot to seal a gap between brake and adapter plate.
Warner Electric also developed a series of static holding brakes for controlling yaw when the wind-turbine nacelle is positioned into the wind. For this technically simpler application, the yaw brakes are mounted on the back end of a yaw motor. Typically, each turbine requires three pitch brakes and four to five yaw brakes.
