Hobart 6921 Series Operation And Maintenance Manual page 115

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Protective Circuit (Continued)
Trouble, Symptom & Condition
Load contactor opens during
power delivery. Undervoltage
indicating light ON. (Continued)
3. Load contactor opens during
power delivery. Overfrequency
indicating light (DS 40) ON.
4. Load contactor opens during
power delivery. Under-
frequency light (DS39) ON.
5. Load contactor opens during
power delivery. Indicating light
ON.
February 28/94 Revised
Test or Inspection
c. Defective protective monitor
module (K14).
a. Electric governor
improperly adjusted, or
malfunctioning.
b. Governor improperly
adjusted.
c. Electric Governor System
Malfunctioning.
d. Defective
over-under-frequency
sensing module (K27).
a. Electric governor
improperly adjusted, or
malfunctioning.
b. Governor Improperly
adjusted.
c. Electric governor system
malfunctioning.
d. Defective over-under
frequency sensing module
(K27).
a. There may have been an
overload condition which
caused the overload device
(k4) to function normally.
Corrective Action
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.
Proceed as follows:
Adjust in accordance with Sect.
2-3, Para. 3, E, (3).
Check and adjust or repair in
accordance with ENGINE AND
CONTROLS Troubles 8 and 9.
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.
Proceed as follows:
Adjust in accordance with Sect.
2-3. Para. 3, E, (3).
Check and adjust or repair in
accordance with ENGINE AND
CONTROLS Troubles 8 and 9.
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.
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.
Chapter 3-1
Page 23