TM 55-4920-221-14
NOTE
(7) Rotate dc ammeter terminal selector (43)
Leave regulator-voltage adjusting
in ALT. EXC position, and read field current on dc
ammeter (11).
potentiometer in position, giving a
minimum voltage.
(8) Rotate circuit selector switch (56) and
(m) Rotate app. switch (23) in CENTER
three-phase ammeter and wattmeter range selector,
(57) in position for three-phase input. Read power on
position, and move dc voltmeter circuit selector (16) to
three-phase wattmeter (39) and current on three-phase
BATT. V position.
ammeter (5).
(n) Start external generator and operate
NOTE
at rated rpm.
It
is
normal
for
three-phase
(o) Position battery switch (33) in ON
wattmeter (39) to indicate a reading
position.
with voltage applied but with no
(p) Rotate field rheostat (44), slowly
current flowing.
increasing voltage of external generator until 1.5 to 2
(9) Rotate
single-phase
ammeter
and
volt higher reading is indicated on dc voltmeter (13) than
wattmeter range selector (64) in position for single-
was indicated with test generator voltage in paragraph
phase input. Read power on single-phase wattmeter
(g) above.
(38) and current on single-phase ammeter (4).
(q) Rotate app. switch (23) in SWITCH
(10) Rotate voltmeter phase selector (59) on
position and move de voltmeter circuit selector (16) .to
line as phase position. Read voltage on ac voltmeter
DIFF. V position.
(40).
(r) Slowly increase test generator
(11) Position high-low switch (7) and the switch
voltage by adjusting regulator-voltage adjusting
on phase sequence indicator (60) in HIGH or LOW
potentiometer, simultaneously depressing dc voltmeter
position, depending on frequency of equipment under
switch (17). Observe maximum reading on dc voltmeter
test.
(13). Highest voltage attained is the differential voltage.
(12) Observe lamps on phase sequence
(s) Rotate dc voltmeter circuit selector
indicator (60) to determine phase sequence for three-
(16) to GEN. V position.
phase input. Lamp 1-2-3 should light for correct phase
(t) Slowly decrease test generator
sequence. If lamp 3-2-1 lights, reverse any two leads
voltage with regulator-voltage adjusting potentiometer,
on T1, T2, or T3 terminals (37).
and note maximum reverse-current reading on the dc
CAUTION
Always perform phase sequence test
current attained is reverse-current reading for relay
on three-phase ac equipment before
under test.
applying load to prevent damage to
(u) Rotate app.
switch (23) and
three-phase wattmeter (39).
rheostat test switch (25) in CENTER position.
(13) Depress LOAD ON pushbutton of load
(v) Place all switches in OFF position.
disconnect switch (21).
Close ac generator load
Stop both external and test generators and disconnect
switches (49) and increase load on generator in
leads.
increments until rated load is reached.
d. Ac Generator Test.
(14) Adjust T1 variable control (63), T2
(1) Perform operations as described in
variable control (61) and T3 variable control (46) for 0 to
1 kw variation in load for each leg, T1, T2, and T3
(2) Connect leads of generator under test to
terminal (37).
A10 terminal (2, figure 6) and N terminal (36) for single-
(15) Depress OFF pushbutton of load
phase input.
disconnect switch (21) and place switches in OFF
(3) Connect generator leads to their
position upon completion of tests.
respective T1, T2, T3 terminals (37), and ,N terminal
(16) Stop generator under test and remove
(36) for three-phase, four-wire input.
external leads.
(4) Connect generator field leads to their
e. Ac Voltage Regulator Test.
respective A+, F, and A- terminals (54), and connect ac
(1) Perform operations as described in
regulator terminals to ac voltage regulator terminals
(48).
(2) Connect regulator leads to corresponding
(5) Biting generator under test to operating
ac voltage regulator terminal (48, figure 6).
speed.
(3) Repeat ac generator test in paragraph (d)
(6) Rotate ammeter phase selector switch
above.
(55) in position and read current in each leg, T1, T2, or
T3 on the three-phase ammeter (5).
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