Hobart 60PL20 Operation And Maintenance Manual page 61

(16) Release the switch (17) and allow it to return to the center ON position. The load contactor
should open immediately, and the generator "on" indicating light should go OFF. This is because the
plug interlock relay (Ref. 1-1; 1, Fig. 8) is not receiving power from an outside source of 28 V DC. It in-
dicates that the plug interlock contacts are OPEN as they should be when the interlock coil is not re-
ceiving 28-V DC power.
(17) Open and lower the front door panel of the control box and place the test bank switch (26, Fig. 1)
in TEST BANK position.
(18) Again place the load contactor switch (17) in the top, CLOSE position. Light (19) should glow
GREEN and remain ON when the switch is released and allowed to return to the center ON position.
This indicates that the test bank switch (26) is functioning to bypass the plug interlock relay.
(19) Return the test bank switch to AIRCRAFT position. The load contactor should open at once and
the green indicating light (19) should go off.
(20) Connect a source of 24-V DC power (two twelve-volt batteries connected in series) to terminals
"N" and "E-F" at the output terminal panel.Connection polarity should be: MINUS to terminal "N" and
PLUS to terminal "E-F".
(21) With test-bank switch in AIRCRAFT position, hold the contactor operating switch (17) in top,
CLOSE position momentarily. The generator "on" indicating light (19) should glow GREEN and re-
main on when the switch is released and allowed to return to the center ON position. This indicates
that the load contactor is closed and the plug interlock relay is functioning properly.
(22) Apply 1/3 to 1/2 load at the load bank and allow the unit to run for 15 to 30 minutes. Observe op-
eration of all monitoring instruments.
(23) Increase load bank resistance to apply a full load.
(24) Check operation of the governor by observing the frequency meter (1, Fig. 1) when generator is
switched from no-load to full-load and vice versa. Use the contactor control switch (17) to apply and
remove load several times. Frequency drop should be no more than 1 Hz. Adjust governor if neces-
sary (See Para. 3, E, (3)).
(25) Follow instructions in Para. 3, B, (2) (b) to set voltage regulator line-drop compensation potenti-
ometers (Ref. Figure 1, items (28) and (30) . Set knob pointer on cable size potentiometer (28) to size
(2/0, 4/0, etc.) of cable being used. Set knob pointer on cable length potentiometer (30) to length (20
feet, 40 feet, etc.) of cable being used. See instruction plate (mounted below knobs) .
(26) Check voltage regulator, at intervals, from no-load to full load, and on up to 125% load. Observe
and note voltage at various loads. Voltages should vary no more than plus or minus 1% from 115 V.
(27) Check accuracy of voltmeter.
(a) Open and lower the front door panel of the control box and connect a master voltmeter of
known accuracy to terminals of the voltmeter (2).
(b) Compare unit voltmeter reading with master meter. Error must not exceed 2% of full scale.
(28) Check accuracy of AC ammeter.
(a) Connect a master ammeter of known accuracy to the AC ammeter (3) terminals.
(b) Compare unit ammeter reading with master meter under various loads. Error must not exceed
4% of full scale.
(29) Check operation of meter selector switch (4) . A voltage value should be shown in each switch po-
sition, except when the switch handle is on the DOWN (OFF) position.
December 31/91 Revised
OM-2053
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