Hobart 6921 Series Operation And Maintenance Manual page 112

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Generator and Excitation Circuit (cont.)
Trouble, Symptom & Condition
Load contactor (K1) will not
close when control switch (20,
Fig. 1 is held in CLOSE
position. Generator running at
normal voltage. No fault lights
on. (cont.)
4. Load contactor (K1) will close
when control switch (20, Fig. 1
is held in momentary CLOSE
position. Opens immediately
when switch is released to
center ON position.
Chapter 3-1
Page 20
Test or Inspection
d. Defective load contactor
control switch (S5)
(20, Fig. 1).
e. Defective rectifier (CR6)
1-1; 5, Fig. 11).
a. 28.5-V DC is not reaching
plug-interlock relay (K2)
from aircraft for the
following reasons:
b. Generator to aircraft cable
connector defective or not
plugged into aircraft
receptacle connector.
c. Aircraft rejecting power.
Corrective Action
Set AUTO-MANUAL switch (S1)
to AUTO position. connect a
jumper with test prods between
terminals "S" and "R" on the test
receptacle. If the contactor
closes, replace control switch.
Check rectifier output as follows:
With test receptacle terminals
"S" and "R" connected as above,
check voltage to rectifier
between terminals "R" and "H".
Voltage should be 115-V AC.
With test receptacle terminals
"S" and "R" connected as above,
check rectifier output at load
contactor terminals X and Y. If
voltage is not at least 90 V DC,
replace rectifier.
Defective load contactor coil
(K1) )1-1; 6, Fig. 11)
Disconnect leads at load
terminals W and V. Check coil
resistance between these
terminals. Resistance should be
approximately 50 ohms. If coil is
defective, replace the complete
load contactor.
Check voltage at terminal Z on
test receptacle. Voltage should
be 28.5-V DC. If not, voltage is
not being supplied from aircraft.
Check causes as follows:
Inspect cable connector plug
thoroughly for damaged E and
F terminals. Be sure the plug is
fully mated with the aircraft
receptacle connector and
making good contact.
Check aircraft on board
electrical equipment and
controls.
February 28/94 Revised