When choosing a tolerance fit of 3 phase electric ac motors' bearing, in addition to the general rules, some other important factors should be considered, such as the external conditions of bearing rotation, the load borne by the bearing, and the actual operating environment.

Bearing rotation conditions refer to the bearing ring relative to the load, such as rotating load, static load and variable load. Rotating load refers to when the bearing ring is rotating and the load is fixed in a certain direction, or the bearing ring is stationary and the load is rotating, then the bearing ring in the process of rotating a week, all points on the raceway are subjected to the load.

Under rotating load, the bearing ring with clearance fit may rotate between it and the mating surface and cause the contact surface to wear, that is, the running ring of the bearing, so the bearing ring with rotating load must use interference fit, in view of this requirement, it is easier for us to understand the mating relationship between the motor bearing and the shaft, as well as the bearing and the end cap bearing chamber.

When the bearing ring of 3 Phase Induction Motor is stationary and the load has a fixed direction, or the bearing ring and the load rotate at the same speed, then the load always acts on the same position on the raceway, which is called stationary load. In this case, there is generally no rotation between the bearing ring and its mating surface. Therefore, unless there are other reasons, the bearing ring does not need interference fit.

Variable load refers to some changes in external forces, impact loads, as well as vibration and imbalance in high-speed machinery generated by the load. In this case, the direction of the load will also change, so it is impossible to accurately judge. When the direction of the load cannot be determined, especially in the case of heavy load, it is best to use interference fit for both bearing rings. However, if the outer ring is required to move axially freely in the bearing seat, under conditions where the load is not very large, a slightly looser tolerance can be used than in the rotating load.