Problem
Cause
Motor runs, but shuts
• Voltage drops.
off.
• Load increase.
The motor vibrates.
• Unbalanced load.
• Unbalanced rotor.
• Defective motor bearings.
• Motor misaligned with load.
• Too much backlash at motor ends.
• Defective windings.
Run capacitor failure.
• Possible power surge in the motor caused
by lightning or other high transient voltage.
• Ambient temperature is too high.
Starting capacitors
• The motor starts too often.
are constantly failing.
• Motor is not coming up to speed fast
enough.
A loud rubbing or
• The starter switch may be defective,
squeaking noise is
preventing the motor from coming out of
produced at start-up.
the starter winding.
• Motor voltage is too low.
• The rotor may be hitting the stator.
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Troubleshooting
Solution
• If the voltage is less than 10% of the motor rating,
contact the power company.
• Check to see if any other equipment is drawing
power from the motor and if the motor is running on
an extension cord. Verify that the extension cord is the
proper gauge for the motor current.
• Remove the load from the motor for inspection.
Verify that the shaft is not bent. Rule of thumb:
0.001"deflection per inch of shaft length.
• Remove the load from the motor to inspect it. If it
feels rough and vibrates but the bearings are OK, the
rotor may have been improperly balanced at the
factory. Refer to a
Service Center for repair.
• If the bearings are bad, you will hear a noise or feel a
roughness. Go to a
Service Center to replace the bearings. Add grease if
the bearings have fittings.
• Realign the load.
• With the motor disconnected from power, rotate the
shaft. It should move, but with some resistance. If the
shaft moves in and out freely, this indicates a preload
problem and the bearings may need additional shims.
• Check to see if the winding is shorted or open. Amps
may also be high. Refer to a
thorized Service Center for repair.
• This is a common problem. Install an over voltage
protector or motor protector relay.
• Verify that the ambient temperature does not exceed
the motor nameplate.
• Check the duty cycle. Capacitor manufacturers
recommend no more than 20 starts of three-second.
Install a capacitor with a higher voltage rating or add a
bleeder resistor to the capacitor.
• The motor may not be properly sized. Check the time
it takes for the motor to reach speed. Most
single-phase motors with starting capacitors should
reach speed in three seconds. If not, the capacitors
may be failing.
• Replace the switch.
• Verify that the motor voltage is within 10% of the
nameplate value.
• Make sure that the motor has not been damaged
during transport.
• Damage to the frame may not be repairable. If you
cannot see physical damage, inspect the motor rotor
and stator for scuff marks. If there are signs of scuffing,
the motor should be replaced. Sometimes, simply
disassembling and reassembling the motor will
eliminate the scuffing.
Sometimes end bells become misaligned during
shipping.
Authorized
Authorized
Au-
