Protective Circuit - Hobart 90CU24 Operation And Maintenance Manual

OM-2084 / Operation and Maintenance Manual
90CU24 / Series 500392 Generator Sets
No. 2 Load Contactor Operating Circuit (500392-002 and -004 only)
Trouble, Symptom
and Condition
3. Contactor opens during power
delivery. NO fault indicating
lights on.

Protective Circuit

Trouble, Symptom
and Condition
NOTE: Protective relays and protective monitor are not completely functional until load contactor is
CLOSED. Since it is not advisable to vary voltages for test purposes while delivering power to an aircraft,
generator should be connected to a load bank for trouble shooting protective circuits.
To avoid repetition, it will be assumed that reset push button switch (19, Fig. 2) has been pushed and load
contactor has been closed before commencing each test.
1. Load contactor opens during
power delivery. Over voltage
indicating light ON.
Chapter 2-4
Page 20
Probable Cause
a. No. 2 load contactor relay
(K272) (5, Fig. 3) on
generator control PC board,
or the PC board itself, could
be defective
b. A fault has developed in
load contactor holding
circuit.
c. Cable accidentally
disconnected from aircraft.
Probable Cause
a. Over voltage condition may
have been result of a
sudden drop in load, or
possible tampering with fine
or course voltage regulator
potentiometers (36 or 37,
Fig. 2), and may have been
a normal action.
Test, Check, And/or
Remedy
Replace relay K272 and again
close contactor. If contactor still
opens, try replacing the PC
board to correct this malfunc-
tion. Proceed with trouble-
shooting as follows if
malfunction is not corrected.
If load contactor cannot be
closed by operation of output
No. 2 push button switch
(S275) (22, Fig. 2), check circuit
in accordance with instructions
in Trouble 1, above under
LOAD CONTACTOR
OPERATING CIRCUIT. If load
contactor can be closed, but
opens as soon as power
accepted push button switch
(S275) is released, check for
trouble under Trouble 2, above.
Reconnect cable.
Test, Check, And/or
Remedy
Press reset push button switch
(19, Fig. 2) and resume power
delivery. Observe voltmeter (13,
Fig. 2) to be certain voltage is
normal 115 V-AC. Adjust to
normal if necessary. If load
contactor is opened again and
an over voltage condition is
indicated by OV indicating light,
proceed to step b.
November 27/1997