The yaw reducer is generally a vertical planetary reducer, and the pinion gear at the end meshes with the yaw large ring gear, and is driven by a motor to realize yaw wind or unwinding. The yaw brake requires a hydraulic source and control unit. In the braking state, the working oil pressure is high to make the nacelle fixed. When the yaw is against the wind, the brake is changed from the braking state to the damping state with a back pressure of 20-30 bar, so the movement is stable. When the cable is unwrapped under the specified climatic conditions, the brake is changed to the release state, and the cabin is reversed and untwisted.
The yaw system of the rolling bearing has the advantages of simple structure, reliable wind and no sliding, and is easy to maintain; the friction damping torque is not large when the yaw is against the wind, and the wind is stable. The disadvantage is that the cost is higher.
This kind of yaw system sometimes has seal oil leakage and noise: when the friction material is unevenly distributed, the friction pair material does not match, it will cause vibration when working, resulting in noise; multiple yaw causes the friction surface to wear locally, or the brake caliper The installation is not parallel, resulting in increased local friction and noise. The sealing ring is subject to heat aging, which in turn affects the life of the sealing ring. Once the brake seal is broken, oil leakage will occur, affecting the yaw braking force, and the friction surface will be stained with oil. After the yaw rotation, the surface of the friction plate forms a glaze layer, resulting in friction. The coefficient decreases and the braking effect deteriorates. The above problems can be completely solved by selecting high quality brakes and carefully manufacturing and installing the components of the yaw system. At present, most of the yaw brakes installed in China's wind turbines are imported from abroad, and the domestically produced yaw brakes are about 20% or less, mainly produced by Jiaozuo Russel Disc Brake Co., Ltd., which has more than ten connections with the wind power market. Over the years, large-scale production has been formed. After nearly ten years of market testing, the products can meet the requirements of use and can replace imports.
It is very common for modern large wind turbine yaw systems to use fixed rolling yaw with rolling bearings. For example, foreign REpower's MD77-1.5MW, REpower5M-5MW; Nordex's N60-1300kW; GE's GE-1.5s-1.5MW, GEWindenergy3.6MW; Dewind's D6-1MW, D8-2MW. Domestic wind turbines
1.5MW, 2MW and 3MW (more than 20 have been transferred), Huachuang 1.5MW, Dongqi 1.5MW and 3MW, Huarui 3MW are all using such yaw system.
Regarding the power problem of the yaw drive. During the operation of the wind turbine, when the wind is adjusted, the power of the yaw drive should overcome the yaw resistance M. The following aspects should be considered when calculating the yaw resistance torque:
M=Mf+Mw+Mp+Mz+Mtv
Where: Mf--the frictional resistance torque of the slewing bearing; Mw--the wind resistance torque caused by the wind pressure acting on the wind wheel and the nacelle; Mp--the inertia resistance caused by the inertia moment in the unit when the yaw is started Moment; Mz--damping torque caused by the damping mechanism; Mtv--the yaw resistance torque caused by the torque component generated by the inclination of the main shaft of the wind turbine.
For example, a 1.5MW fixed rolling bearing yaw, the sum of Mf and Mz is 40%-50% of the M value. If damper sliding bearing yaw is used, Mf will decrease, and Mz will increase, eventually yaw The power impact of the drive unit is not large.
Questions about the hydraulic system. In fixed yaw, the yaw brake and the high speed axle brake form a hydraulic system (hydraulic station). Even with damped yaw, a high speed axle brake requires a hydraulic system (hydraulic station).
development trend
At present and in the future, fixed yaw is still the mainstream. Most of the models independently developed in China are fixed yaw, especially for large units of 3MW and above, which are fixed yaw.
