Axial load assessment and load-bearing capacity selection of vertical motor thrust bearings

1. Function and classification of vertical motor thrust bearings
Thrust bearings are mainly used to bear axial loads, that is, to support and position the motor rotor in the axial direction. Due to the structural characteristics of vertical motors, their rotors naturally sag under the action of gravity. Therefore, thrust bearings not only need to bear the entire weight of the rotor, but also need to cope with dynamic axial force changes during startup, shutdown and operation. Thrust bearings are mainly divided into two categories: rolling thrust bearings and sliding thrust bearings. The former relies on rolling elements to transfer loads and is suitable for high-speed and high-precision occasions; the latter supports loads through oil films or solid lubricating layers and is mostly used in heavy-load, low-speed or self-lubricating occasions.

2. Axial load assessment method
Basic load calculation: First, the weight of the motor rotor needs to be accurately calculated, which is the most basic axial load of the thrust bearing. Usually, the rotor weight can be directly calculated through parameters such as material density and volume in the design drawings.
Dynamic load analysis: In addition to static weight, the dynamic axial force of the motor during operation must also be considered, such as the instantaneous impact force at startup and the axial force fluctuation caused by load changes. These dynamic loads can be estimated by dynamic simulation software or empirical formulas.
Safety margin setting: To ensure the long-term reliability of thrust bearings, a certain safety margin must be considered during the evaluation. Generally, the recommended safety factor is 1.2 to 1.5, and the specific value should be determined based on the operating environment, maintenance conditions and expected life of the motor.
3. Principles for selecting thrust bearing load capacity
Matching load requirements: According to the results of the axial load evaluation, select thrust bearings with a load capacity not less than the calculated load. Note that the load capacity not only refers to the static load capacity, but also the fatigue life under dynamic conditions.
Speed ​​and lubrication considerations: For rolling thrust bearings, it is necessary to ensure their stability at the highest speed of the motor, and select appropriate lubrication methods and lubricants to reduce friction losses and increase bearing life. Sliding thrust bearings need to pay attention to oil film thickness, viscosity-temperature characteristics of lubricating oil, etc.
Size and installation restrictions: The selection of thrust bearings also needs to consider the overall size restrictions and installation convenience of the motor. Oversized bearings may increase the axial length of the motor and affect the compactness of the overall structure; oversized bearings may fail prematurely due to insufficient load capacity.
Economy and maintainability: Under the premise of meeting performance requirements, the cost-effectiveness and maintainability of the bearing should be taken into account. For example, choose a bearing type that is easy to replace and has low maintenance costs, and consider the supply and after-sales service of the bearing.