Classification and Technical Requirements of Motor Bearings Internal Reference

Wind turbines are generally divided into doubly fed, direct drive, and semi direct drive types. Various types of motor bearings are widely used in wind turbines, and the traditional doubly fed wind turbine has the largest number and most complete types of bearings. A wind turbine can use up to 32 sets of bearings. So choosing the right bearings is very important to ensure the safe and stable operation of wind turbines.

Wind turbines are installed in areas with high wind and sand or humidity in the wild. The working conditions of wind turbine bearings are very harsh, and they need to withstand a wide range of temperature, humidity, and load changes. Especially for yaw and pitch bearings, they need to withstand large axial forces and overturning moments, while gearbox bearings need to withstand huge impact loads during startup and braking. At the same time, it is also required that the gearbox bearings of the wind turbine have the characteristics of low friction torque and high operational flexibility during low-speed startup.

Wind turbine bearings are generally divided into the following types: yaw bearings, pitch bearings, spindle bearings, gearbox bearings, and generator bearings. The technical requirements vary depending on the type of bearing.

1. Bearings such as yaw and pitch bearings are generally designed as assemblies, using single row four point contact ball turntable bearings or double row four point contact ball turntable bearings, which should meet the following technical requirements:

Four point contact ball bearing

According to the force characteristics of the fan bearings, the yaw bearings adopt small clearance, and the pitch bearings adopt four point contact ball bearings with zero clearance or "negative clearance" design. The channel needs to be specially designed and processed to withstand large axial and torque loads. The yaw gear in the assembly should be selected with appropriate materials, modules, tooth profile, and hardness to ensure a matching lifespan with the driving gear. At the same time, targeted heat treatment measures should be taken to improve the tooth surface strength, so that the bearing has good wear resistance and impact resistance. Due to the exposure of the fan to the wild, there are strict requirements for the sealing performance of the bearings. It is necessary to optimize the sealing form of the bearings to ensure that the bearing life is the same as the fan life. Fans are installed at heights of over 50 meters or even hundreds of meters, and the cost of installation and dismantling is expensive. Therefore, they must have very high reliability, generally requiring a lifespan of 20 years. In addition, the bearing structure is complex, so the requirements for design and manufacturing are extremely high. 2. Spindle bearings

The main shaft bearings are generally self-aligning roller bearings, and there are also those that use large cone angle double row tapered roller bearings. Most impeller main shafts are supported by two self-aligning roller bearings. Due to the large load borne by the impeller spindle and the long shaft, which is prone to deformation, it is required that the bearing must have good centering performance.

Double row tapered roller bearings

3. Gearbox bearings

There are many types and quantities of gearbox bearings, including deep groove ball bearings, cylindrical roller bearings, full roller cylindrical roller bearings, double row tapered roller bearings, self-aligning roller bearings, thrust self-aligning roller bearings, and four point contact ball bearings.

The bearings in the gearbox are mainly lubricated by the gear oil in the gearbox. There are many metal particles in the lubricating oil, which can significantly affect the bearing life. Therefore, special heat treatment processes are needed to create compressive stress on the surface of the raceway, reduce the sensitivity of the raceway to particle impurities, and improve the bearing life. At the same time, it is also necessary to adjust the working conditions of the bearings