ABB Low Voltage Motors Manuel D'installation, D'exploitation Et De Maintenance page 20

TROUBLE
Motor takes too long to
accelerate and/or draws
high current
Wrong rotation direction
Motor overheats while
running
Motor vibrates
Scraping noise
Noisy operation
Hot bearings
EN-20
CAUSE
Excessive load
Low voltage during start
Defective squirrel cage rotor
Applied voltage too low
Wrong sequence of phases
Overload
Frame or ventilation openings may
be full of dirt and prevent proper
ventilation of motor
Motor may have one phase open
Grounded coil
Unbalanced terminal voltage
Motor misaligned
Weak support
Coupling out of balance
Driven equipment unbalanced
Defective bearings
Bearings not in line
Balancing weights shifted
Contradiction between balancing of
rotor and coupling (half key - full key)
Polyphase motor running single phase
Excessive end play
Fan rubbing end shield or fan cover
Loose on bedplate
Air gap not uniform
Rotor unbalance
Bent or sprung shaft
Excessive belt pull
Pulleys too far away from shaft shoulder
Pulley diameter too small
Misalignment
Insufficient grease
Deterioration of grease or lubricant
contaminated
Excess lubricant
Overloaded bearing
Broken ball or rough races
WHAT TO DO
Reduce load.
Check for high resistance. Make sure that adequate cable
size is used.
Replace with new rotor.
Correct power supply.
Reverse connections at motor or at switchboard.
Reduce load.
Open vent holes and check for a continuous stream of air
from the motor.
Check to make sure that all leads are well connected.
Motor must be rewound
Check for faulty leads, connections and transformers.
Realign.
Strengthen base.
Balance coupling.
Rebalance driven equipment.
Replace bearings.
Repair motor.
Rebalance motor.
Rebalance coupling or motor.
Check for open circuit.
Adjust bearing or add shim.
Correct fan mounting.
Tighten holding bolts.
Check and correct end shield fits or bearing fits.
Rebalance rotor.
Straighten or replace shaft.
Decrease belt tension.
Move pulley closer to motor bearing.
Use larger pulleys.
Correct by realignment of the drive.
Maintain proper quality and amount of grease in bearing.
Remove old grease, wash bearings thoroughly in kerosene
and replace with new grease.
Reduce quantity of grease, bearing should not be more
than half full.
Check alignment, side and end thrust.
Replace bearing, clean housing thoroughly first.
ABB/Manual for Low Voltage Motors 01-2009