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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
Table 4-4. AC synchronous motor trouble-shooting-continued.
Maintenance
Probable Cause
Trouble
C h e c k c i r c u i t c o nnections. Be
No field excitation.
Fails
to
pull
into
contactor is
sure field-applying
step.
operating.
Check for open circuit in field or
exciter.
Check exciter output.
Check rheostat.
Set rheostat to give rated field
currant when field is applied.
Check contacts of switches.
Reduce load
Load excessive.
Check operation of reloading
device (if any) on driven machine.
May be misapplication
-
consult
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.
motors.
Check
field ammeter and
its shunt to be
sure reading is
not higher than
actual currant.
Locate and repair break.
Open circuit in field
and exciter circuit
Check with low voltage and
Short circuit in
polarity indicator and repair
field.
field.
Check with low voltage and
Reversed field spool.
polarity indicator and reverse
incorrect leads.
See motor "hunts" below.
Load fluctuates
widely.
Check driven machine for bad
Excessive torque
adjustment,
or consult motor
peak.
manufacturer.
Re-establish power circuit.
Power fails.
raise
Increase if possible,
Line voltage too low.
excitation.
4-34
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