Yaw brakes keep the nacelle in the right direction
June 2, 2011 by Paul Dvorak
Filed under Maintenance & operations, Turbine Blades, Wind Power News
Continuously alternating between brake and release necessitates low-wear components with a locking force of up to 500 kN or 50 tons per brake.
German manufacturer KTR has extended its product range for wind turbines with recent yaw brakes. The KTR-Stop Yaw brake makes sure that the nacelle is held in a required direction. It differs from a rotor brake in that the azimuth system is always active. When the nacelle turns, the Yaw brake is controlled so it produces 10 to 20 % of their retention force. In this way, azimuth (yaw) drives are protected against impacts and pulsating loads. Brakes used this way typically have clamping forces of about 500 KN or 50 tons. Large wind turbines can have azimuth brakes with up to 10 calipers positioned to accept high loads which correspond to twisting of the nacelle even during extreme wind loads.
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.
Yaw brakes for wind turbines
January 13, 2010 by Paul Dvorak
Filed under Yaw and Pitch Brakes
All four models of Twiflex yaw brakes function as static-holding brakes for keeping the nacelle positioned into the wind.
A full array of caliper designs is available from Twiflex, Ltd. to meet the yaw braking-force requirements of any size wind turbine. All brake models are durable, hydraulically activated, and direct applied. Models T20 and T40 deliver up to 40 kN braking force, feature two-bolt side mounting, and are intended for light to medium-duty applications. Model VCH provides 60 kN, features four-bolt center mounting, and works well in medium-sized turbines. Model VKH generates 118 kN, and is a base mounted caliper for larger, heavy-duty turbines.
There typically are four to five yaw motors per wind turbine. The brakes mount to the back end of the drive motors and are commonly positioned on the underside of the yaw gear ring. Twiflex is a member of the Altra Industrial Motion family of power transmission companies.
New, longer lasting brake pads for wind turbine
August 20, 2009 by Windpower Engineering
Filed under Yaw and Pitch Brakes
Tribco Inc. will exhibit brake pads that last 3 to 5 times longer than conventional brake pads—but won’t scratch or wear down brake rotors—because they are lined with Braketex, the world’s first and only 100% Kevlar fibered composite friction lining.
Wind turbine brake pads
Braketex is also virtually dust free whereas conventional linings generate dirty, abrasive black dust that contaminates lubricants and damages electronics and other critical components. Additionally, Braketex is environmentally friendly because it does not contain asbestos or other harmful ingredients.
Braketex-lined brake pads are ideal for wind turbine mechanical and yaw brakes—and help reduce maintenance downtime and expense while increasing turbine, reliability, up-time and output.
Tribco stocks replacement brake pads and clutch plates for many applications and will also custom fabricate new parts to order or reline used metal plates and carriers.
Overall, Tribco’s exclusive 100% KEVLAR fibered composite friction lining has been performance proven in thousands of dry and wet brake, clutch, PTO, power transmission, torque converter, synchronizer and other friction applications worldwide for over 25 years.
This includes aerospace, agriculture, aviation, construction, defense, forestry, manufacturing, marine, material handling, metal forming and stamping, mining, oil, packaging, paper, printing and trucking industry applications to name a few.
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.
