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OM-2031
TROUBLE, SYMPTOM
AND CONDITION
PROTECTIVE CIRCUIT
NOTE: The protective relays and protective monitor are not completely functional until the load contactor
is CLOSED. Since it is not advisable to vary voltages for test purposes while delivering power to an
aircraft, the generator should be connected to a load bank for trouble shooting the protective circuits.
To avoid repetition, it will be assumed that the reset switch [(36), Fig. 1] has been pushed and the load
contactor has been closed beforecommencing each test.
1. Load contactor
opens during power
delivery. Overvoltage
indicating light ON
2. Load contactor
opens during power
delivery. Under-
voltage indicating
light ON.
3-1
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PROBABLE CAUSE
A. The overvoltage con-
dition may have been
the result of a sudden
drop in the load,
or possible tampering
with voltage regulator
rheostat, and
may have been a
normal action.
B. Defective over-under-
voltage sensing module
(K26)
A. An undervoltage con-
dition caused the
over-undervoltage
sensing module (K26)
to function normally.
Trouble Shooting Chart (Sheet 16 of 20)
Figure 5
TEST, CHECK, AND/OR
REMEDY
A. Press reset switch (36,
Fig. 1) and resume power
delivery. Observe voltmeter
(2, Fig. 1) to be certain
voltage is normal 115 V AC.
Adjust to normal if necessary.
If the load contactor
is opened again and an over-
voltage condition is indicated
by light (DS 37), proceed
to step B.
B. Use voltage adjusting rheostat
to reduce voltage
to 110 V AC. Observe
voltmeter and gradually
increase voltage with rheostat.
If the over-under-
voltage sensing module (K26)
functions to open the load
contactor at any value less
than 134 V AC, it is defective.
Replace over-undervoltage
module or complete
protective relay tray.
A. Observe generator voltage on
voltmeter and adjust to normal
115 V AC with voltage
regulator rheostat.
Resume normal operation.
If the load contactor
opens again and an undervoltage
condition is indi-
cated by light (DS38), proceed
August 5/89 Revised
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