Common Causes of Electric Motor Bearing Failures and How to Prevent Them

The Crucial Role of Bearing Systems in Electric Motor Performance

The bearing system plays a critical role in ensuring the mechanical performance of electric motors. When issues arise in the bearing assembly, the consequences range from increased noise to more severe effects on overall motor functionality.

One common issue is improper fitment. If the bearing fits too tightly with mating components—such as the shaft or the bearing housing—it can significantly affect operational quality. Excessive friction may occur, causing abnormal heat generation and potentially leading to fatigue spalling of the raceways or rolling elements. On the other hand, if the bearing fits too loosely, it may result in bearing creep and heat build-up, further damaging the motor.

Lubrication failures are another major factor. Inadequate lubrication causes the bearing to operate under dry friction, leading to overheating and even sintering in severe cases. Causes of lubrication failure include the use of improper grease, rotor axial displacement, or the presence of shaft currents. The grease fill should be properly calibrated—neither too little nor too much. Maintenance schedules must be tailored to the motor's actual operating conditions to ensure consistent performance.

Vibration is also a critical indicator of bearing issues. It often manifests as abnormal noise and heat. Common causes include rotor-stator misalignment, shaft deflection, bearing wear, and improper mounting. Persistent vibration leads to fatigue damage and gradual bearing failure.

In harsh operating environments, external contaminants can cause bearing rust or enter the bearing cavity, compromising internal cleanliness. Motors used in such conditions must have protective measures in place according to their ingress protection (IP) ratings.

Special attention is needed when angular contact bearings are used, as they require precise installation direction. Incorrect orientation can cause immediate noise and premature failure of the bearing system.

From manufacturing to long-term operation, the proper maintenance and inspection of the bearing system is essential. Routine checks, including dimensional verification of bearing-related parts, should be a fundamental part of any motor maintenance program.