Protective Circuit (Continued)
Trouble, Symptom & Condition
Test or Inspection
Corrective Action
Load contactor opens during
power delivery. Undervoltage
indicating light ON. (Continued)
c. Defective protective monitor
module (K14).
With unit running normally, use
voltage regulator adjustment
potentiometer ( 37, Fig. 1 ) to
reduce voltage quickly to 90-V. If
the light is turned ON
immediately, the protective
monitor circuitry is defective.
Replace the protective relay tray.
3.
Load contactor opens during
power delivery. Overfrequency
indicating light (DS 40) ON.
a. Electric governor
improperly adjusted, or
malfunctioning.
Proceed as follows:
b. Governor improperly
adjusted.
Adjust in accordance with Sect.
2-3, Para. 3, E, (3).
c. Electric Governor System
Malfunctioning.
Check and adjust or repair in
accordance with ENGINE AND
CONTROLS Troubles 8 and 9.
d. Defective
over-under-frequency
sensing module (K27).
If overfrequency nuisance
tripping continues after
governor system is proven to
be good, and an overfrequency
condition does not exist,
replace over- underfrequency
module (K27), or complete
protective relay tray.
4.
Load contactor opens during
power delivery. Under-
frequency light (DS39) ON.
a. Electric governor
improperly adjusted, or
malfunctioning.
Proceed as follows:
b. Governor Improperly
adjusted.
Adjust in accordance with Sect.
2-3. Para. 3, E, (3).
c. Electric governor system
malfunctioning.
Check and adjust or repair in
accordance with ENGINE AND
CONTROLS Troubles 8 and 9.
d. Defective over-under
frequency sensing module
(K27).
If overfrequency nuisance
tripping continues after
governor system is proven to
be good, and an under
frequency condition does not
exist, replace over- under
frequency module (K27), or
complete protective relay tray.
5.
Load contactor opens during
power delivery. Indicating light
ON.
a. There may have been an
overload condition which
caused the overload device
(k4) to function normally.
Observe ammeter ( 4, Fig. 1 ).
Check for abnormal overload
condition and correct. If
overload device functions too
open the load contactor when
an overload does not exist,
proceed to step B.
OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
February 28/94 Revised
Chapter 3-1
Page 23
Summary of Contents for 6921 Series
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