Motor Bearing Overheating: 3 Key Factors for Effective Control

Control of Bearing System Overheating in Motors: Focus on These 3 Key Factors!

Overheating in bearing systems is a common failure issue faced by many electric motors. Both bearing manufacturers and motor manufacturers pay special attention to this problem. The direct consequences of bearing overheating include grease leakage, bearing component failure due to excessive heat, restricted or stuck rotor movement, and in severe cases, rapid winding burnout caused by heat transfer and increased current.

To prevent such failures, many large and high-voltage motors are equipped with temperature and vibration monitoring devices. However, the most critical aspect is ensuring that the motor bearing system itself meets quality requirements. The following three points are key to controlling bearing overheating:

1.Compliance of Bearing Clearance
Different types of bearings require a safe range of operating clearance. Ensuring this depends on the proper radial fit between the bearing’s inner ring and shaft, and between the outer ring and the housing. This fit relationship is fundamental to controlling the bearing system’s performance.

2.Ensuring No Relative Movement of Inner and Outer Rings

In theory, once mounted, the bearing’s inner and outer rings should remain firmly in contact with their mating components, without relative sliding during motor operation—commonly referred to as “creep.” In many real-world failure cases, improper fits have caused ring creep, leading to excessive heating, grease degradation and loss, and eventually catastrophic bearing collapse.

3.Damage from Shaft Currents

Shaft currents are a challenge for high-voltage motors, inverter-driven motors, and large low-voltage motors. Many bearing failures are caused by electrical erosion from shaft currents, leaving patterned damage marks on the rolling surfaces. Early symptoms include abnormal noise and overheating, followed by rapid bearing breakdown. To address this, manufacturers adopt protective measures such as grounding carbon brushes, insulated bearings, insulated end shields, and insulated sleeves, as well as improvements in motor electromagnetic design and inverter configuration.