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Both vertical and horizontal motors share several structural similarities, particularly in their use of bearings to support the rotor. These bearings are crucial for ensuring smooth and stable motor operation by managing the forces exerted by the rotor’s weight. Despite these similarities, the orientation of the motor significantly influences how these forces are distributed and managed by the bearings.
The orientation of the motor affects the nature of the forces acting on the bearings. In a horizontal motor, the bearings at both ends support the rotor’s weight as a radial load, distributing the load equally. Conversely, in a vertical motor, the rotor’s weight becomes an axial load. This shift requires the bearings to handle a different type of force, impacting their design and selection.
In horizontal motors, the primary load on the bearings is radial, resulting from the gravity of the rotor. This radial load, applied perpendicular to the shaft’s axis, is shared by both bearings. This configuration ensures that the rotor remains balanced and operates efficiently, with the bearings providing the necessary support and stability.
In vertical motors, the gravity of the rotor exerts an axial load along the motor shaft. Unlike in horizontal motors, where the bearings handle radial loads, the bearings in vertical motors are designed to support this axial force. This change necessitates bearings that can manage significant axial loads to maintain the rotor’s position and ensure proper motor function.
For a simplified analysis, it is assumed that no external axial or radial forces act on the motor apart from the rotor’s weight. Additionally, any radial load resulting from air gap asymmetry due to slight misalignments between the stator and rotor centerlines is ignored. These assumptions help focus on the primary forces affecting the bearings, providing a clearer understanding of their roles in different motor orientations.
Motor bearings are typically configured with one end positioned and the other end floating. The positioning end bearing is designed to handle axial loads, ensuring the rotor remains correctly aligned. The floating end bearing accommodates radial loads and allows for thermal expansion and slight misalignments without imposing additional stresses on the bearings.
The fixed or positioning end bearing supports both axial and radial loads, providing stability and precise alignment of the rotor. In contrast, the floating end bearing primarily manages radial loads, allowing for axial movement due to thermal expansion or other factors. In vertical motors, the rotor’s weight acts as an axial force on the positioning end bearing, requiring it to support this load without significant wear or failure.
To clarify, the terms “shaft extension end” and “non-shaft extension end” are used. The shaft extension end is where the motor shaft extends out of the motor housing, often used to connect to other mechanical components. The non-shaft extension end is the opposite side of the motor.
The principles governing bearing configuration and load distribution remain consistent regardless of whether the shaft extension end is positioned above or below in a vertical motor. The key consideration is ensuring that the positioning end bearing, which handles the axial load, is appropriately designed and maintained to support the rotor’s weight and any additional forces encountered during operation.
Three aspects to note:
1.Selection of bearings at both ends
Since the positioning end bears axial force, the positioning end needs to select a bearing that can withstand the axial force. The non-positioned end does not matter. The most common selection is that deep groove ball bearings, angular contact ball bearings, etc. can withstand axial loads and can be used as positioning ends; NU/N series cylindrical roller bearings cannot withstand axial loads and cannot be used as positioning ends. Spherical roller bearings can bear axial loads, but when bearing axial loads, one of the two rows of rollers will easily be overloaded, so specific analysis of actual problems is required.
2.There is a radial load on the shaft extension end.
If there is an external radial load on the shaft extension end, when the bearing is also subjected to the gravity of the rotor (axial force), the force on the shaft extension end bearing will be relatively large; looking at the other end, there seems to be no load on the non-shaft extension end. . When this situation occurs, the bearing size at the bearing end will be larger, and the bearing at the non-extension end will be smaller. Such bearing size matching will cause an imbalance in performance and cost. Not only is it not economical, it may also cause bearing problems.
3.Convenience of maintenance
When maintaining bearings, consider the load conditions of the bearings at both ends. Since the positioning end bearing bears combined loads (axial and radial), it requires more maintenance and will face more frequent disassembly. Then, when the bearing that requires more maintenance is placed at the non-extension end of the shaft, when performing maintenance, it is necessary to consider whether there will be additional steps in disassembling the fan, windshield and other components. We cannot answer in one word whether it is better to place the positioning end bearing of a vertical motor on the top or bottom. Each choice needs to adapt to the corresponding working conditions. Only after understanding the basic principles can we adapt to changes and make appropriate choices.
Conclusion
In conclusion, understanding the structural similarities and differences between vertical and horizontal motors, particularly in terms of bearing forces and configurations, is crucial. By comprehensively analyzing the forces acting on the bearings and considering the implications of different bearing configurations, we can make informed decisions to optimize motor design and maintenance. This approach ensures efficient and reliable motor operation across various applications.
