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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
Table 4-3. AC induction motor trouble-shooting-continued.
Maintenance
Probable Cause
Trouble
Reduce load
Fails to pull into
Load excessive
step (cont'd).
Check operation of loading
device (if any) on driven machine.
- consult
May be a misapplication
Inertia of load
excessive.
manufacturer.
Increase excitation.
Exciter voltage low.
Motor pulls
out of
step or trips
Examine exciter as shown in D. C.
breaker.
Check field ammeter and
motors.
its shunt to be sure reading is
not higher than actual current.
Locate and repair break.
Open circuit in field
and exciter circuit.
Check with low voltage and
Short circuit in
p o l a r i t y indicator a n d r e p a i r
field.
field.
spool.
Check with lO w voltage and
Reversed field
polarity indicator and reverse
incorrect leads.
See motor "hunts",
below.
Load fluctuates
widely.
Check driven machine for bad
Excessive torque
or consult motor
adjustment,
peak.
manufacturer.
Re-establish power circuit.
Power fails.
Raise
Increase if possible.
Line voltage too low.
excitation.
Correct excessive torque peak at
Fluctuating load.
driven machine or consult rotor
manufacturer.
If driven machine is a compressor
check valve operations.
Increase or decrease flywheel
size.
Try decreasing or increasing motor
field current.
Realign and shim stator or
in
Rotor not centered.
Stator overheats
spots .
Check connections and correct.
Open phase.
improper
Loose connections;
Unbalanced
internal connections.
Replace or repair.
Short circuit in a
Field overheats.
field coil.
Reduce excitation until field
Excessive field
current is at nameplate value.
current.
4-31
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