Maintaining yaw and pitch drives is a challenge because of the inherent time that it takes for maintenance personnel to ascend to the nacelle. But foregoing maintenance can lead to costly failures and even more downtime. The Magnashear motor brake from Force Control Industries eliminate pitch drive maintenance by eliminating the root cause of maintenance required for traditional dry braking systems – degradation of friction material. Oil Shear technology is a unique technology which transmits torque between lubricated surfaces – thereby eliminating wear on friction surfaces. A patented fluid recirculation system dissipates heat thus eliminating heat build-up which causes friction material glazing, another common problem in dry braking systems which requires adjustment. Oil Shear eliminates the wear and thus the need for adjustment, and significantly increases service life (typically to 5-10x that of dry braking systems). Oil shear technology also provides a smooth “cushioned” stop which reduces shock to the drive system, further extending service life of downstream components. The totally enclosed, IP56 rated, Magnashear brakes are impervious to moisture, dirt and dust and are ideal for critical wind turbine applications such as pitch drive systems. 

Pitch Drive

A turbine’s pitch system is used to change the upwind area of the blades when the rotor is facing the wind. Adjusting each blade’s angle with respect to the wind controls the rotor’s speed, thus the amount of energy produced. Each blade is equipped with a motor and fail-safe, electromagnetic brake to lock blades in position when not actively pitching. Conventional dry-friction brakes experience friction material degradation and need to be adjusted periodically. If not properly adjusted, the brake could slip leading to overspeed or energy efficiency loss. In the case of a coil failure, the brake may not release when pitching resulting in driving through the brake, generating heat and destroying internal friction services. Keeping turbines positioned toward to the wind is critical for turbine operators’ revenue, and blade angle asymmetry can lead to costly maintenance costs for equipment down the line.

How Oil Shear Works

Unlike dry brakes, oil shear technology includes a layer of automatic transmission fluid between the brake disc and the drive plate. As the fluid is compressed, the fluid molecules shear – thus imparting torque to the other side. This torque transmission causes the stationary surface to turn, bringing it up to the same relative speed as the moving surface. Since most of the work is done by the fluid particles in shear, wear is virtually eliminated. Elimination of wear also eliminates the need for adjustments which are common for dry braking systems.

In addition to transmitting torque, a patented fluid recirculation system helps to dissipate heat which is the major problem with traditional dry brakes.  

Along with heat removal and torque transmission, the fluid serves to continually lubricate all components of the oil shear brake, elongating their service life.  

Magnashear brakes with oil shear technology provide significantly longer service life, characterized by virtually maintenance-free operations.  

Suitable for a Wide Range of Motor Sizes

These proven motor brakes are available to accommodate a wide range of applications. Spring set torque ratings from 3 to 1250 foot-pounds are available. Magnashear motor brakes can be sized to the correct torque independent of the motor frame size or horsepower.

Magnashear motor brakes feature “quick mount” features for quick and easy mounting to drive motors in NEMA frame sizes 56 to 449.  They are shipped ready to install, with no assembly or adjustments required. They are also available pre-mounted on a motor for severe duty applications.  Magnashear motor brakes can be furnished to fit a NEMA or IEC frame motor, as a complete motor and brake assembly, or to mount on a machine frame or other special mounting configuration.  

Force Control Industries | www.forcecontrol.com