Heat generation is an inevitable phenomenon during bearing operation. Under normal circumstances, the heat generation and heat dissipation of the bearing will reach a relative balance, that is, the heat generated and the heat dissipated are basically the same, so the bearing system will maintain a relatively stable temperature state.
Based on the quality and stability of the bearing material itself and the lubricating grease used, the bearing temperature of the motor product is controlled with 95℃ as the upper limit. This ensures the stability of the bearing system and does not have a significant impact on the temperature rise of the motor windings.
The main causes of heat generation in bearing systems are lubrication and proper heat dissipation. However, during the actual manufacturing and operation of motors, unsuitable factors can cause the bearing lubrication system to malfunction.
When a bearing's operating clearance is too small, or when the bearing runs out of its housing due to loose fit between the bearing and shaft, or axial force causes severe misalignment in the bearing's axial fit, or when improper fit between the bearing and related components causes grease to be ejected from the bearing cavity, these adverse conditions can all lead to bearing overheating during motor operation. The grease will then degrade and fail due to excessive heat, causing a catastrophic failure of the motor's bearing system within a short period. Therefore, it is crucial to control the dimensional relationships between components during motor design, manufacturing, and subsequent maintenance.
Shaft current is an unavoidable quality hazard in large motors, especially high-voltage and variable-frequency motors. Shaft current poses a very serious problem to the motor's bearing system. Without necessary measures, the bearing system may collapse within tens of hours or even hours due to shaft current. In the early stages of this type of failure, it manifests as bearing noise and overheating, followed by the failure of the lubricating grease due to heat, and then, within a very short time, the bearing seizes due to burning. Therefore, high-voltage motors, variable-frequency motors, and low-voltage high-power motors all take necessary measures during the design, manufacturing, and use stages. Two common methods are: one is circuit-breaking measures (such as using insulated bearings and insulated end caps), and the other is current bypass measures, which use grounding carbon brushes to divert the current and prevent damage to the bearing system.
