TM 55-4920-221-14
60. LOAD DISCONNECT SWITCH.
54. DC VOLTMETER CIRCUIT SELECTOR.
The load disconnect switch (21, figure 6) is used
'The dc voltmeter circuit selector (16, figure 6) is
for loading and disconnecting test stand loads. To apply
used to select DIFFERENTIAL, BATTERY, INVERTER,
loads position fan OFF-ON switch (10) to ON, depress
GENERATOR INPUT, PILE, EQUALIZER, EXCITER, or
the LOAD ON pushbutton, applying load determined by
EXTERNAL voltages, depending on the test being
the unit under test. To deenergize contactors, depress
performed. To read DIFFERENTIAL or EQUALIZER
LOAD OFF pushbutton which drops test stand load.
voltage, depress the dc voltmeter switch (17).
NOTE
55. FIELD RHEOSTAT.
The field rheostat (44, figure 6) is used for
It is impossible to apply load unless
controlling the output voltage of dc generators under
fan switch (10) is in ON position.
test, or external generators used in testing reverse-
61. EQUALIZER COIL TEST SWITCH.
current cutouts. To control the voltage of generators
Equalizer coil test switch (22, figure 6) is used
under test, rotate rheostat test switch (25) to the TEST
for testing voltage drop on equalizer coils. Depressing
GENERATOR position, and rheostat regulator switch
the switch should indicate a 2-volt drop in generator
(26) to RHEOSTAT position.
To control external
output voltage on the dc voltmeter (13).
generator voltage, rotate rheostat test switch to
62. AUXILIARY POWER PACK (APP.) SWITCH.
BATTERY GENERATOR position, and rheostat
The app. switch (23, figure 6) is a three position
regulator switch (26) to the REGULATOR position.
toggle switch used for testing APP and SWITCH circuits
56. DC VOLTMETER SWITCH.
of reverse-current cutout relay. Rotate the switch in
The dc voltmeter switch (17, figure 6) is used for
APP position to operate relay.
Under operating
reading voltage on the 3.5-volt scale of the dc voltmeter
conditions, rotate switch to SWITCH position for testing
(13) when using the external voltmeter terminals (19), or
reverse-current cut-out, using polarized circuit. Center
when using the dc voltmeter circuit selector (16) on
position is provided for leaving relay circuit open.
DIFFERENTIAL or EQUALIZER voltage.
63. PHONE JACK.
57. UNEXCITED BUS TEST INDICATOR.
The phone jack (24, figure 6) measures the
When unexcited bus test indicator (18, figure 6)
noise level of the carbon pile, when testing dc voltage
lights, it indicates closing of the main contacts on the
regulators.
current cutout relay, when using the unexcited bus test
64. RHEOSTAT SWITCH.
switch (20).
The rheostat test switch (25, figure 6) is used for
58. EXTERNAL VOLTMETER TERMINALS.
placing the field rheostat (44) in test, or in external
Three external voltmeter input terminals (19,
generator field circuit. Rotate rheostat switch to TEST
GENERATOR position for field rheostat to control test
on dc voltmeter (13). To measure external voltage,
generator voltage. Rotate rheostat regulator switch (26)
rotate de voltmeter circuit selector (16) to EXTERNAL
to BATTERY GENERATOR position for field rheostat to
VOLTS position. Dc voltmeter switch (17) must be
control external generator voltage.
depressed to indicate a reading on the 3.5 scale of the
65. RHEOSTAT REGULATOR SWITCH.
dc voltmeter (13).
Rheostat regulator switch (26, figure 6) is used
59. UNEXCITED BUS TEST SWITCH.
for placing external regulator or field rheostat (44) in
The unexcited bus test switch (20, figure 6) is a
field circuit of generator under test. Rotate rheostat
spring loaded toggle switch used for testing minimum
regulator switch to REGULATOR position for operation
current needed to keep reverse-current cutout coil
with regulator. Rotate the rheostat regulator switch (26)
energized. Hold switch in ON position to place a
to RHEOSTAT position, and rheostat test switch (25) to
minimum load on the coil, and observe unexcited bus
TEST GENERATOR position for operation with field
test indicator which will light when main relay contacts
rheostat (44).
close.
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