The bearing system is a very crucial quality and operational element of motor products. The overheating of bearings is often the main cause of bearing system failure. Overheating of bearings can lead to the degradation and failure of bearing grease, causing deformation of the inner and outer rings and cages of the bearings. In mild cases, it results in bearing noise problems; in severe cases, it leads to the scrapping of the entire motor due to bearing system burnout. For basic series motors, problems with the bearing system are relatively fewer, and regular maintenance and care in accordance with the motor’s usage and maintenance requirements can suffice. However, for motors used with frequency conversion, as well as low-voltage high-power and high-voltage motors, problems with the bearing system are relatively more frequent and more difficult to solve.
Analysis and Summary of the Causes of Motor Bearing Heating
(1) The matching issue between tolerance fits and the operating conditions of the motor. Regarding this problem, we have conducted specific analysis and discussion in the dedicated article on motor bearings. Especially for different series of bearings, the satisfaction of their normal working clearance depends on the dimensional tolerances of associated components. For example, the working clearance of deep groove ball bearings should be controlled to zero clearance or a slightly pre-tightened negative clearance. While the working clearance of cylindrical roller bearings should be positive clearance. Even if it is very small, it must exist. Regarding this aspect, we will not elaborate on it here. However, in practical applications, there are often situations where the bearing fit is not suitable for some reasons, or due to interference fits, the working clearance is inappropriate, and there are also cases where the bearing runs out of place due to excessive fit clearance. All of these will cause the motor bearing system to collapse within a short period of time.
(2) The problem of bearing burnout caused by electrochemical corrosion. This issue is the same as the axial current problem we previously discussed. The necessary condition for the occurrence of axial current is the axial voltage and a closed circuit. For motors used under variable frequency conditions, as well as high-power and high-voltage motors, different degrees of axial voltage will be generated. When the insulation performance of the lubricant cannot withstand the axial voltage, a large axial current will form a closed circuit through the bearing and cause burnout problems for the components of the bearing system. In the early stage of burnout, it is manifested as bearing noise accompanied by heat. In a very short period of time, due to the damage of bearing components and the heat problem, the bearing system will suffer from a serious failure.
There are many problems caused by axial current. Some motors may operate abnormally for a period of time, while others may suffer severe failures within a few hours. Regarding this issue, it is often regarded as a bearing quality problem. Repeated replacement of bearings will not solve the problem. Taking necessary measures during the design and manufacturing stages, as well as choosing higher-quality frequency converters during use, are very effective and necessary measures.
(3) Heating problems caused by the unsuitability of the lubrication system. We have discussed this issue in many previous articles. One situation is the unsuitability of the design itself. The oil chamber of the bearing is too large and cannot form a good circulation, which will cause the bearing to malfunction; too much grease is filled in the bearing system, resulting in poor heat dissipation; the grease does not match the operating conditions, causing the grease to degrade due to heat or form lumps due to cold, both of which will lead to the bearing overheating due to poor lubrication; especially during the operation of the motor, regular maintenance and upkeep are particularly important.
(4) Problems related to bearing overheating caused by motor temperature rise or operating environment temperature. Some motors have inherent deficiencies and suffer from high temperature issues. While some motors operate in harsh environments, such as air compressor motors operating in high-temperature conditions, this poses a significant challenge to the bearing system. In light of this problem, comprehensive consideration should be given to the bearing material and the performance of the lubricating grease to avoid the occurrence of quality issues in the bearing system.
Of course, there are many other reasons that can lead to quality problems in the bearing system. However, as long as the key points are addressed and the root causes of the problems are identified, the safety and stability of the motor bearing system quality can be ensured.
Post time: Jul-07-2025