22
Troubleshooting
Trouble
Cause
Remedy
Motor Will Not Start
Power not available at motor terminals
• Check power at starter. Correct any bad connections
between the control apparatus and the motor.
• Check starter contacts and control circuit. Reset overloads,
close contacts, reset tripped switches or replace failed control
switches.
• If power is not on all leads at starter, make sure overload
and short circuit devices are in proper condition.
Wrong connections
Check motor and control connections against wiring diagrams.
Low voltage
Check nameplate voltage against power supply. Check
voltage at motor terminals.
Open circuit in motor winding
Check stator windings for open circuits.
Motor or fan drive stuck
Disconnect motor from load and check motor and Geareducer
for cause of problem.
Rotor defectve
Look for broken bars or rings.
Unusual Motor Noise
Motor running single-phase
Stop motor and attempt to start it. Motor will not start if single-
phased. Check wiring, controls, and motor.
Motor leads connected incorrectly
Check motor connections against wiring diagram on motor.
Ball bearings
Check lubrication. Replace bad bearings.
Electrical unbalance
Check voltages and currents of all three lines. Correct if
required.
Air gap not uniform
Check and correct bracket fits or bearing.
Rotor unbalance
Rebalance.
Cooling fan hitting guard
Reinstall or replace fan.
Motor Runs Hot
Wrong voltage or unbalanced voltage
Check voltage and current of all three lines against nameplate
values.
Overload
Check fan blade pitch. See Fan User Manual. Check for
drag in fan drive train as from damaged bearings.
Wrong motor RPM
Check nameplate against power supply. Check RPM of motor
and gear ratio.
Bearings overgreased
Remove grease reliefs. Run motor up to speed to purge
excessive grease.
Rotor rubs stator bore
If not poor machining, replace worn bearing.
Wrong lubricant in bearings
Change to proper lubricant. See motor manufacturer's
instructions.
One phase open
Stop motor and attempt to start it. Motor will not start if single-
phased. Check wiring, controls, and motor.
Poor ventilation
Clean motor and check ventilation openings. Allow ample
ventilation around motor.
Winding fault
Check with Ohmmeter.
Bent motor shaft
Straighten or replace shaft.
Insufficient grease
Remove plugs and regrease bearings.
Deterioration of grease, or foreign
material in grease
Flush bearings and relubricate.
Bearings damaged
Replace bearings.
Motor Does Not Come Up
To Speed
Incorrect fan blade pitch
See Fan User Manual for blade pitching instructions.
Voltage too low at motor terminals
because of line drop
Check transformer and setting of taps. Use higher voltage on
transformer terminals or reduce loads. Increase wire size or
reduce inertia.
Broken Rotor bars
Look for cracks near the rings. A new rotor may be required.
Have motor service person check motor.
