What’s the Causes of motor bearing heating and damage?

Good lubrication is a necessary condition for the normal operation of bearings. For motor products, to ensure the normal operation of the bearing system, it should be analyzed and solved from many aspects such as bearings, greases, and associated parts. In the previous topic, we talked about the problems caused by the protection of the assembly process, the tolerance of the associated parts, and the coaxial degree of the fixed rotor. Today we focus on the impact of lubrication on the operation of the motor bearing.

(1) The matching relationship between the performance of grease and the operating condition of the three phase motor. The standard operating environment of the motor will be specified in the technical conditions of the motor, such as ambient temperature, altitude, etc., the standard motor will select the grease in accordance with the conditions, but for the motor operating in a special environment, the operating environment may be harsh, such as high temperature environment, low temperature environment, etc.
For a particularly cold climate, the grease must have sufficient low temperature resistance, I have personally experienced a number of motors, big cold days after the motor from the warehouse, the hand motor can not turn, power operation has obvious noise, running for about 5 minutes the motor sound normal. It was checked that the grease used by the motor did not meet the requirements. Similarly, for motors operating in high temperature environments, such as air compressors, especially in the southern region where the temperature is higher, most air compressors operating environment temperature above 40 degrees, coupled with the temperature rise of the motor, the bearing system temperature will be very high, ordinary grease will degrade and fail due to high temperature, resulting in the loss of bearing grease, and the bearing is in a non-lubricated state. In a very short time, the bearing is heated and damaged, and in serious cases, the winding is burned due to high current and high temperature.

(2) Bearing heat caused by excessive grease. From the point of view of heat conduction, the bearing will also generate heat during operation, and the heat will be distributed through the associated parts, and when the grease of three phase induction motor is too much, it will accumulate in the bearing system cavity, which is not conducive to the heat dissipation. Especially for bearing systems with large internal cavities, the problem is more serious. We have done a test, using the infrared instrument to test the temperature of the bearing system, for the relatively high temperature point to check, found that the bearing outer cover parts of the grease accumulation, the temperature dropped naturally after removal.
This involves two problems, one is the filling amount of grease, and the other is a very important problem of the design of bearing associated parts, mainly involving the oil baffle and bearing inner and outer covers.

(3) The rationality of the design of bearing system components. Many motor manufacturers have improved the design for the bearing system parts, in addition to the matching tolerances we talked about in the previous period, the bearing inner cover, bearing outer cover and oil baffle plate have been improved to ensure the proper grease circulation during the bearing operation, ensure the necessary needs of bearing lubrication, and prevent the heat resistance problem of too much grease filling.
(4) Regular replacement of grease. When the motor is running, the grease should be replaced according to the frequency of use. The original grease should be cleaned during the replacement process and the grease of the same brand should be replaced. For this problem, the normal manufacturer will mark the grease replacement cycle and the specific brand.