Protective Circuit
Trouble, Symptom
Test, Check, And/or
and Condition
Probable Cause
Remedy
4.
Load contactor opens during
power delivery. Over frequency
indicating light (DS40) ON.
a.
Electric governor system
malfunctioning
Check and adjust or repair in
accordance with governor
system information listed in this
chapter under ENGINE AND
CONTROLS.
b.
Defective over-under-
frequency PC board
(K27)(1-1; 5, Fig. 6).
If over-under frequency tripping
continues after governor
system is proven to be good,
and an over frequency condition
does not exist, replace over-
under frequency PC board (K27)
5.
Load contactor opens during
power delivery. Under-
frequency light 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 governor
system information listed in this
chapter under ENGINE AND
CONTROLS.
d.
Defective over-under-
frequency PC board (K27)
If under frequency tripping
continues after governor
system is proven to be good,
and an under frequency
condition does not exist,
replace over-under frequency
PC board.
6.
Load contactor opens during
power delivery. Overload
indicating light ON.
a.
There may have been an
overload condition which
caused overload device
(K4).
Observe ammeter (12, Fig. 2).
Check for abnormal overload
condition and correct. If
overload device functions to
open load contactor when an
overload does not exist,
proceed to step B.
b.
One of resistors across an
overload transformer may
be open circuited. Check
resistors (R26, R27, and
R28).
An open resistor will cause a
higher than normal voltage.
Refer to 1-1; 7 and 8, Fig. 9 for
exact location of these
resistors. Check resistors.
Replace any resistors found to
be defective.
c.
Overload device printed
circuit board defective (K4)
Replace overload PC board
(Sect. 1-1; 11 or 12, Fig. 9) with
an overload module known to
be operating properly.
OM-2084 / Operation and Maintenance Manual
90CU24 / Series 500392 Generator Sets
Chapter 2-4
November 27/1997
Page 22