How to determine the motor bearing temperature is too high and how to solve it?
Since the bearings are widely used in three-phase asynchronous motors, there are not many failures of the three-phase asynchronous motors caused by the bearings. The fault of the motor bearing is mostly caused by overheating of the bearing. Let's explore how to discriminate motor bearings from overheating and malfunctions and solutions.
First, the motor bearing overheating
At present, the motor manufacturer's bearing temperature before the motor leaves the factory is an item that must be checked. In addition to the high temperature not exceeding the 95 °C limit, there is no uniform standard for the high temperature of the bearing below the high temperature during operation. According to the general habit, after the motor runs for 1.5-2 hours, the bearing temperature is stable and the temperature rises ≤35K, which can be considered normal. However, when the bearing runs for a short time (such as 15min) and rises to 65°C or runs for more than 1.5h, it still has no downward trend, and less than 1.5h but the bearing stable temperature exceeds 75°C. Both can be considered as high bearing temperatures (65 ° C, 75 ° C for summer, 55 ° C, 65 ° C in cold winter).
Second, the failure phenomenon and solution
1. The bearing is squeezed
Balls or rollers can be easily rotated in the raceway because of the play between them and the inner jacket of the bearing. If the inner or outer ring of the bearing sleeve is squeezed, the clearance is reduced. Because the value of the bearing clearance is small, it is sensitive to changes in the clearance. The clearance becomes smaller, and the bearing rolling body and the ferrule generate a large contact stress, which increases the friction and heat of the bearing.
The countermeasures against extrusion are as follows:
(1) When the bearing is in hot state, the inner ring is greatly expanded, which may cause a negative play. A small amount of negative clearance is beneficial to the normal operation of the bearing, but the larger negative clearance is unfavorable for the bearing operation, the temperature is higher, and the degree of negative clearance is reduced by the expansion of the outer ring. In addition, when the bearing is running, the outer ring of the bearing and the bearing sleeve must also have an interference, and the rolling element is squeezed, causing the bearing to be damaged prematurely due to heat generation.
First, the motor bearing overheating
At present, the motor manufacturer's bearing temperature before the motor leaves the factory is an item that must be checked. In addition to the high temperature not exceeding the 95 °C limit, there is no uniform standard for the high temperature of the bearing below the high temperature during operation. According to the general habit, after the motor runs for 1.5-2 hours, the bearing temperature is stable and the temperature rises ≤35K, which can be considered normal. However, when the bearing runs for a short time (such as 15min) and rises to 65°C or runs for more than 1.5h, it still has no downward trend, and less than 1.5h but the bearing stable temperature exceeds 75°C. Both can be considered as high bearing temperatures (65 ° C, 75 ° C for summer, 55 ° C, 65 ° C in cold winter).
Second, the failure phenomenon and solution
1. The bearing is squeezed
Balls or rollers can be easily rotated in the raceway because of the play between them and the inner jacket of the bearing. If the inner or outer ring of the bearing sleeve is squeezed, the clearance is reduced. Because the value of the bearing clearance is small, it is sensitive to changes in the clearance. The clearance becomes smaller, and the bearing rolling body and the ferrule generate a large contact stress, which increases the friction and heat of the bearing.
The countermeasures against extrusion are as follows:
(1) When the bearing is in hot state, the inner ring is greatly expanded, which may cause a negative play. A small amount of negative clearance is beneficial to the normal operation of the bearing, but the larger negative clearance is unfavorable for the bearing operation, the temperature is higher, and the degree of negative clearance is reduced by the expansion of the outer ring. In addition, when the bearing is running, the outer ring of the bearing and the bearing sleeve must also have an interference, and the rolling element is squeezed, causing the bearing to be damaged prematurely due to heat generation.
