Bearing arrangement of large motor and application of spherical roller bearing and spherical roller thrust bearing
01 Jul,2022
Many motors in industrial applications are large motors, such as power plants, steel mills, large-megawatt wind turbines, etc., so this article focuses on the bearing configuration of large motors and spherical roller bearings used in large motors Roller thrust bearing expertise.
1. Bearing configuration of large motors
The main function of the bearing is to transmit the load while rotating, so whether it is a small motor or a large motor, it is nothing more than that the load that the bearing needs to transmit is different, then the final result is that the size or shape of the bearing changes. Large motors use more bearings with rolling element contact as line contact. For example: cylindrical roller bearings, spherical roller bearings, and spherical roller thrust bearings.
When selecting bearings for large motors, more consideration is given to the load carrying capacity. Bearings with linear contact (section) are more suitable for applications with large loads because of the large contact area between the rolling elements and the raceway, and the correspondingly high bearing capacity. However, the bearing capacity and speed performance of the bearing are the two sides of the coin. In conventional bearing design, the larger the bearing capacity, the lower the speed performance.
2. Spherical Roller Bearings (Spherical Roller Bearings)
As the name suggests, this bearing is center-adjustable. So what is "adjustable" It does not mean that the size center or load center of the bearing itself can be adjusted, but that the bearing can be used in applications with a certain eccentricity without affecting the normal function of the bearing.
The theoretical state of a rotating machine is that the trajectory of the rotating shaft is a straight line. However, under actual working conditions, first, there are machining errors and installation errors in various parts of the motor; second, the gravity and magnetic pulling force of the motor; third, the rotating shaft of the motor is not an ideal steel body, and bending deformation will occur. Yes, these actual trajectories that lead to the axis of rotation may be a spindle, or an hourglass shape.
Deformed shafts create additional bearing internal loads on the bearings. For example, when a cylindrical roller or deep groove ball bearing is selected for the bearing, in addition to the external load including the rotor weight and magnetic pull, the bearing is also subjected to what is called an "internal load", which is caused by the deformation of the shaft. load.
This kind of load is one of a series of loads that the designer did not take into account when selecting bearings, or theoretically cannot be accurately calculated. Therefore, this "unaccounted for" load on the bearing can lead to premature bearing failure, or other wear that exceeds the design expectations.
But the self-aligning series of bearings, the biggest function is to offset the eccentricity inside the bearing, so that even if the bearing runs under the eccentricity condition (within a certain range), it will not lose its normal function. And this series of functions are achieved through the special design of the contact surface between the rolling element and the outer ring raceway. In layman's terms, the outer raceway of this bearing is part of the "great circle through the sphere". The outer raceway of the bearing is part of the "great circle through the sphere". This bearing has very good eccentricity adjustment performance, but this bearing is one of the few designs with two rows of rolling elements. Therefore, although the bearing can bear axial load and radial load at the same time, the ratio of the load in the two directions is a prerequisite for determining the distribution of the load on the two rows of rolling elements.
3. Spherical roller thrust bearing
As can be seen from the name, the main function of this bearing is to bear thrust load, that is, axial load. Other functions are similar to spherical roller bearings. Under the condition of eccentricity, the normal function of the bearing is not affected.
However, the rotational performance of the thrust bearing itself is very low. Due to the design, the rotational performance of this bearing is greatly reduced, and the control of the rotational speed limit of the bearing will become very strict, and further, the lubrication conditions will become necessary. It is important to consider, for example, the purpose of using steam turbine platinum resistance temperature measurement for steam turbine thrust bearing is to monitor bearing lubrication conditions.
Regarding the bearing configuration of large motors and the content of spherical roller bearings and spherical roller thrust bearings used in large motors, there are still many details worth discussing. For the reason of space limitation, I just throw a brick for you. As for the follow-up, everyone What else would you like to know, we can continue in future discussions.
1. Bearing configuration of large motors
The main function of the bearing is to transmit the load while rotating, so whether it is a small motor or a large motor, it is nothing more than that the load that the bearing needs to transmit is different, then the final result is that the size or shape of the bearing changes. Large motors use more bearings with rolling element contact as line contact. For example: cylindrical roller bearings, spherical roller bearings, and spherical roller thrust bearings.
When selecting bearings for large motors, more consideration is given to the load carrying capacity. Bearings with linear contact (section) are more suitable for applications with large loads because of the large contact area between the rolling elements and the raceway, and the correspondingly high bearing capacity. However, the bearing capacity and speed performance of the bearing are the two sides of the coin. In conventional bearing design, the larger the bearing capacity, the lower the speed performance.
2. Spherical Roller Bearings (Spherical Roller Bearings)
As the name suggests, this bearing is center-adjustable. So what is "adjustable" It does not mean that the size center or load center of the bearing itself can be adjusted, but that the bearing can be used in applications with a certain eccentricity without affecting the normal function of the bearing.
The theoretical state of a rotating machine is that the trajectory of the rotating shaft is a straight line. However, under actual working conditions, first, there are machining errors and installation errors in various parts of the motor; second, the gravity and magnetic pulling force of the motor; third, the rotating shaft of the motor is not an ideal steel body, and bending deformation will occur. Yes, these actual trajectories that lead to the axis of rotation may be a spindle, or an hourglass shape.
Deformed shafts create additional bearing internal loads on the bearings. For example, when a cylindrical roller or deep groove ball bearing is selected for the bearing, in addition to the external load including the rotor weight and magnetic pull, the bearing is also subjected to what is called an "internal load", which is caused by the deformation of the shaft. load.
This kind of load is one of a series of loads that the designer did not take into account when selecting bearings, or theoretically cannot be accurately calculated. Therefore, this "unaccounted for" load on the bearing can lead to premature bearing failure, or other wear that exceeds the design expectations.
But the self-aligning series of bearings, the biggest function is to offset the eccentricity inside the bearing, so that even if the bearing runs under the eccentricity condition (within a certain range), it will not lose its normal function. And this series of functions are achieved through the special design of the contact surface between the rolling element and the outer ring raceway. In layman's terms, the outer raceway of this bearing is part of the "great circle through the sphere". The outer raceway of the bearing is part of the "great circle through the sphere". This bearing has very good eccentricity adjustment performance, but this bearing is one of the few designs with two rows of rolling elements. Therefore, although the bearing can bear axial load and radial load at the same time, the ratio of the load in the two directions is a prerequisite for determining the distribution of the load on the two rows of rolling elements.
3. Spherical roller thrust bearing
As can be seen from the name, the main function of this bearing is to bear thrust load, that is, axial load. Other functions are similar to spherical roller bearings. Under the condition of eccentricity, the normal function of the bearing is not affected.
However, the rotational performance of the thrust bearing itself is very low. Due to the design, the rotational performance of this bearing is greatly reduced, and the control of the rotational speed limit of the bearing will become very strict, and further, the lubrication conditions will become necessary. It is important to consider, for example, the purpose of using steam turbine platinum resistance temperature measurement for steam turbine thrust bearing is to monitor bearing lubrication conditions.
Regarding the bearing configuration of large motors and the content of spherical roller bearings and spherical roller thrust bearings used in large motors, there are still many details worth discussing. For the reason of space limitation, I just throw a brick for you. As for the follow-up, everyone What else would you like to know, we can continue in future discussions.
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