42
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 fan drive for cause of
problem.
Rotor defective
Look for broken bars or rings.
Unusual motor noise
Motor running single-phase
Check 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.
Bad 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 end belt 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
drivetrain as from damaged bearings.
Wrong motor RPM
Check nameplate against power supply. Check RPM of motor and drive
ratio.
Bearing over greased
Remove bearing reliefs. Run motor up to speed to purge excessive grease.
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 stat 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.
Too frequent starting or speed changes
Limit cumulative accelerations time to a total of 30 seconds/hour. Set on/
off or speed change set points farther apart. Consider installing a Marley
VFD drive for fine temperature control.
Deterioration of grease or foreign material in grease
Flush bearings and relubricate.
Bearings damaged
Replace bearings.
Motor does not come up to
speed
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.
Wrong motor rotation
Wrong sequence of phases
Switch any two of the three motor leads.
