In our previous discussion, we covered three primary causes of motor bearing overheating. This section expands on other contributing factors and their diagnostic approaches.

4. Bearing-Specific Failures

Wear: Pitting, spalling, cracking → increased clearance/friction

Damage: Cage fracture, roller breakage, raceway scoring

Manufacturing defects: Material, heat treatment, machining errors

Selection errors: Incorrect type (e.g., deep-groove bearings for axial loads), size, or load rating

Electrical Erosion (VFD-Driven Motors):

PWM-induced shaft voltage → oil film breakdown → arcing

Raceway fluting ("washboard pattern") → friction ↑ + high-frequency noise

5. Thermal & Environmental Factors

Poor Heat Dissipation:

Cooling fan failure (damage/reversed rotation)

Blocked ventilation paths (dust/oil/debris)

High ambient temperature (>40°C) or heat sources

Insulating dirt/oil accumulation on housing

Contamination:

Ingress of dust, moisture, or corrosive agents

Internal metallic debris from wear

Effects: Abrasive wear, grease emulsification, corrosion → friction ↑

6. Vibration

External: Unstable mounting or nearby equipment vibration

Internal: Rotor imbalance, bearing defects, electromagnetic forces

Consequence: Impact loading → accelerated wear/heat

Diagnostic Procedure

Temperature Measurement:

Use IR thermometers to record bearing ΔT vs. ambient/housing

Acoustic Analysis:

Screeching (misalignment), clicking (damage), rumbling (contamination)

Vibration Testing:

Measure velocity/acceleration/displacement; focus on high-frequency anomalies

Grease Inspection:

Check color (oxidation), texture (grit → contamination), consistency

Lubrication Audit:

Verify grease type, fill volume, intervals, and seal integrity

Mechanical Checks:

Laser alignment (<0.05mm tolerance), belt tension, shaft straightness

Load & Environment:

Confirm operation ≤ rated load (current measurement)

Inspect cooling systems and housing cleanliness

VFD-Specific Tests:

Monitor bearing noise; measure shaft voltage/current if possible

Teardown Inspection:

Examine wear patterns, fluting, cage integrity, and grease condition

Conclusion

Bearing overheating stems primarily from:

Lubrication failures

Installation/misalignment errors

Overloading

Bearing defects

Electrical erosion (VFD)

Systematic diagnosis requires correlating temperature, acoustic, vibration, lubrication, and operational data. Immediate intervention is critical to prevent catastrophic failure. Provide specific operational details (motor type, load, VFD usage, temperature readings, noise characteristics) for targeted troubleshooting.