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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
Table 4-3. AC indution motor trouble-shooting-continued.
Maintenance
Probable
Cause
Trouble
Replace bearings.
Bearings damaged
Ball bearings
hot
(cont'd. )
(corrosion, etc. )
Check
Check coupling joint.
Coupling loose.
Tighten coupling.
alignment.
Wound rotor motor
troubles
Use larger cable to c o n t r o l .
Wires to
control
too
Motor runs at low
small.
speed with external
resistance cut out.
Bring control nearer m o t o r .
Control too far from
motor.
Test to find open circuit and
Open circuit in rotor
repair.
circuit (including
cable to control).
Check for looseness, overload, or
Brushes sparking.
dirt.
Clean rings and insulation
Dirt between brush
assembly.
and ring.
U s e right size b r u s h , c l e a n
Brushes stuck in
holders.
holders.
Clean brush tension and correct.
Incorrect brush
tension.
Sand and polish.
Rough collector
rings.
Turn in lathe or use portable tool
Eccentric rings.
to true up rings without
disassembling motor.
connectons or
Correct
open
Open rotor circuit.
Excessive vibration
control.
and noise.
Reduce load.
(If brushes have
Current density of
been replaced, make sure they are
brushes too high
of the same grade as originally
(overload).
furnished.
Consult
Low current density.
Ring threading
manufacturer for different brush
recommendation.
I n s p e c t for open or poor
Motor
will
not
start
Faulty Connection.
connect ion.
Test,
locate and r e p a i r .
Open circuit one
phase.
Open and repair.
one
Short circuit
phase.
too
Reduce the impedance of the
Voltage falls
external circuit.
low.
4-29
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