Causes Of Motor Bearings Overheating And Damage (2)

Adequate lubrication is a prerequisite for the normal operation of bearings. For motor products, to ensure the proper functioning of the bearing system, analysis and solutions should be carried out from multiple aspects such as bearings, lubricating grease, and associated components. In the previous discussion, we addressed problems caused by assembly process protection, tolerance matching of associated components, and non-compliant stator-rotor coaxiality. Today, we will focus on the impact of lubrication on the operation of motor bearings.

1. Matching Relationship Between Lubricating Grease Performance and Motor Operating ConditionsMotor technical specifications define the standard operating environment of motors, such as ambient temperature and altitude. Lubricating grease for standard motors is selected in accordance with these conditions. However, motors operating in special environments may face harsh conditions, such as high-temperature or low-temperature settings.

For extremely cold climates, the lubricating grease must have sufficient low-temperature resistance. I once encountered a batch of motors that could not be turned manually after being taken out of the warehouse on a freezing day. When powered on, the motors emitted obvious noise, which returned to normal after approximately 5 minutes of operation. An inspection revealed that the lubricating grease used in the motors did not meet the required standards.Similarly, for motors operating in high-temperature environments-such as air compressor motors, especially in southern regions with high temperatures-most air compressor motors work in ambient temperatures above 40°C. Coupled with the temperature rise of the motor itself, the temperature of the bearing system will become extremely high. Ordinary lubricating grease will degrade and fail due to excessive temperatures, resulting in grease leakage. This leaves the Motor bearings in an unlubricated state, leading to rapid bearing overheating and damage, and in severe cases, winding burnout caused by excessive current and temperature.

2. Bearing Overheating Caused by Excessive Lubricating GreaseFrom the perspective of heat transfer, Motor bearings generate heat during operation, which is dissipated through associated components. Excessive lubricating grease will accumulate in the inner cavity of the bearing system, severely impeding heat dissipation. This problem is particularly acute in bearing systems with larger inner cavities.We once conducted a test using an infrared thermometer to measure the temperature of the bearing system. Inspections of areas with relatively high temperatures revealed a large accumulation of lubricating grease on the outer bearing cap. After removing the excess grease, the temperature dropped naturally.

This phenomenon involves two key issues: one is the proper filling amount of lubricating grease, and the other-an equally critical one-is the rational design of bearing-associated components, mainly the oil baffle discs and inner/outer bearing caps.

3. Rationality of Component Design for the Bearing System Many motor manufacturers have improved the design of bearing-associated components. In addition to the tolerance matching discussed in the previous article, enhancements have been made to the inner bearing caps, outer bearing caps, and oil baffle discs. These improvements ensure the proper circulation of an adequate amount of grease during bearing operation, meeting the essential lubrication requirements of the bearings while preventing heat retention caused by over-greasing.

4. Regular Replacement of Lubricating Grease During motor operation, lubricating grease should be replaced according to the frequency of use. In the replacement process, the old grease must be completely removed, and new grease of the same grade should be refilled. Reputable motor manufacturers typically specify the grease replacement cycle and the exact grease grade in the product manuals.