LEESON AC Motor Trouble Shooting-Guide - Manual (Page 2)

Motor vibrates.
Problem: What To Do: Like Causes:
Motor misaligned to load. Realign load.
Load out of balance.
(Direct drive application.) Remove motor from load and inspect motor by itself. Verify that
motor shaft is not bent. Rule of thumb is .001" runout per every
inch of shaft length.
Motor bearings defective. Test motor by itself. If bearings are bad, you will hear noise or
feel roughness. Replace bearings. Add oil if a sleeve of bearing.
Add grease if bearings have grease fittings.
Rotor out of balance.
Winding may be defective.
Inspect motor by itself with no load attached. If it feels rough and
vibrates but the bearings are good, it may be that the rotor was
improperly balanced at the factory. Rotor must be replaced or
rebalanced.
With the motor disconnected from power turned shaft. It should
move but with some resistance. If the shaft moves in and out too
freely, this may indicate a preload problem and the bearings may
need additional shimming.
Test winding for shorted or open circuits. The amps may also be
high. Replace motor or have stator rewound.
Bearings continuously fail. Load to motor may be excessive or
unbalanced. Besides checking load, also inspect drive belt tension to ensure it’s
not too tight may be too high. An unbalanced load will also cause the
bearings to fail.
High ambient temperature. If the motor is used in a high ambient, a different type of bearing
grease may be required. You may need to consult the factory or
a bearing distributor.
The motor, at start up, makes a
loud rubbing or grinding noise. Rotor may be striking stator. Ensure that motor was not damaged in shipment. Frame damage
may not be repairable. If you cannot see physical damage,
inspect the motor’s rotor and stator for strike marks. If signs of
rubbing are present, the motor should be replaced. Sometimes
simply disassembling and reassembling motor eliminates rubbing.
Endbells are also sometimes knocked out of alignment during
transportation.
Motor may not be sized properly. Verify how long the motor takes
to come up to speed, Most single phase capacitor start motors
should come up to speed within three seconds. Otherwise the
capacitors may fail. Start capacitors continuously fail. The motor is not coming up to speed quickly
enough.
The motor is being cycled too frequently. Verify duty cycle. Capacitor manufacturers recommend no more
than 20, three-second starts per hour. Install capacitor with higher
voltage rating, or add bleed resistor to the capacitor.
Run capacitor fail.
Voltage to motor is too low. Verify that voltage to the motor is within 10% of the nameplate
value. If the motor is rated 208-230V, the deviation must be
calculated from 230V.
Motor Trouble-Shooting Chart
10/13/00 (continued)
Motor may have too much endplay.
Starting switch may be defective, preventing
the motor from coming out of start winding. Replace switch.
Ambient temperature too high.
Possible power surge to motor, caused by
lightning strike or other high transient voltage.
Verify that ambient does not exceed motor’s nameplate value.
If a common problem, install surge protector.
Bulletin 2400 10/00