Analysis of common problems in motor rolling bearing systems

Bearing failure is a relatively concentrated type of motor failure and is closely related to bearing selection, installation and subsequent maintenance. We combine some actual analysis cases and accumulated data to classify the failures and causes of rolling bearing structures and share them with everyone.

1. Analysis of causes of bearing heating

• When single-row ball bearings are used at both ends of the motor, the rotor expands and contracts due to heat, causing the outer sleeve of the bearing to not move smoothly in the bearing box, causing the bearing gap small and subject the ball to additional axial force.
• The bearing is too close to the stator or rotor winding, or is affected by heat radiation from the driven equipment.
• Poor ventilation and heat dissipation at the bearing location.
• Excessive or severe grease loss causes dry wear of the bearing, or there are impurities in the grease.
• The inner sleeve of the bearing does not fit well with the shaft, or the outer sleeve of the bearing and the bearing box are too tight.
• Improper bearing selection: For example, the clearance, model, and limit speed are inappropriate.
• The base is deformed, causing the stops at both ends to be too large coaxially.
• The motor rotor is excessively dynamically balanced.
• The bearing itself is of poor quality.
• Interference from motor-driven equipment.

2. Cause analysis of large motor bearing noise

• Improper selection of bearing clearance.
• Electric motor balance is poor.
• Motor bearing distance is too large.
• Grease is dry or lost.
• Improper matching of bearing inner and outer sleeve with shaft and bearing chamber.
• Uneven load.
• Installation and debugging do not meet the requirements, such as the motor and the dragged equipment coaxial out-of-tolerance.
• The bearing itself is of poor quality, such as loose cage, raceway deformation, etc.

3. Bearing position vibration causes

• Bearing clearance is too large.
• Impurities enter the bearing raceway.
• Bearing distance is too large.
• The rotating shaft is not round, so that the raceway of the bearing inner sleeve is also deformed (also the source of noise).
• Uneven load.
• When the motor is assembled, the bearing is injured, such as knocking the bearing jacket hard, so that the rolling body and raceway are injured.

4. Cause analysis of bearing running ring

• The manufacturer's products are unqualified, more than 90% of the reason is the problem of the motor manufacturer.
• More disassembly times, so that the "knife peak" in the bearing and the coat match is smoothed, the main reason is still in the motor factory, such as poor processing roughness.

5. Bearing cover and shaft friction reason analysis

• Bearing clearance over the rotor sinking.
• The design gap is too small or the manufacturing is out of order.
• Large deformation of parts in use, destroying the coaxial degree of related parts.
• The bearing is seriously heated, causing deformation of related parts.

6. Failure cause analysis of rubber oil seal

• It is not suitable for the relevant parts of the motor.
• Overheating of bearing parts.
• The quality of the oil seal itself is poor.
• Use time is too long.