TM 55-4920-221-14
with field rheostat, then observe dc voltmeter (13).
(b) Connect
relay
leads
to
Voltage should increase and then decrease to zero as
corresponding terminals marked BAT. +, GEN. +,
relay closes. Highest voltage attained is differential
APP., and SW on relay pad (27).
voltage.
NOTE
(p) Slowly decrease generator voltage
Relays with negative strip at
and note maximum reverse-current reading on dc
mounting hole are grounded by left-
hand clamping post.
Use GND
attained is reverse-current reading for relay under test.
terminal on relays without negative
CAUTION
strip.
If relay is defective and does not
(c) Perform operations described in
open, it is possible to draw more
paragraph a(1) through (6) above.
than seven amperes reverse-current
(d) Connect external battery leads to
and damage dc ammeter (11).
battery generator -terminals (34). Battery voltage must
(q) Position battery switch (33) in OFF
correspond to voltage of relay under test.
position.
CAUTION
(r) Upon completion of tests, perform
Check battery with hydrometer to be
operations as described in paragraphs a(13) and (14)
certain it is fully charged. Do not use
above.
dc ammeter as it will be damaged by
(2) External generator.
excessive negative current if battery
is discharged.
(a) Perform operations described in
paragraphs a(1) through (5) above.
(e) Position battery switch (33) in ON
position, de voltmeter circuit selector (16) in BAT. V
(b) Mount voltage regulator to be tested
position. Observe battery voltage on dc voltmeter (13).
as described in paragraphs c(1)(a) and (b) above.
Rotate voltage adjusting potentiometer in midway
(f) Position battery switch (33) in OFF
position.
position and bring generator to operating speed.
(c) Connect POSITIVE and NEGATIVE
(g) Rotate app. switch (23) in APP.
external generator leads to battery-generator terminals
position.
(34) observing polarity and connect external generator
(h) Rotate field rheostat (44) in
field lead to field terminal (52).
clockwise direction. Observe voltage reading on dc
(d) Bring generator under test to
voltmeter (13) to determine relay pickup voltage.
operating speed.
NOTE
(e) Rotate app. switch (23) in SWITCH
Pick up of relay armature is heard as
position.
a loud click.
(i) Rotate field rheostat (44) fully
(f) Rotate field rheostat (44) clockwise,
counterclockwise, and place app.
switch (23) in
note on de voltmeter (13) relay pickup voltage.
SWITCH position.
(g) Determine dropout voltage by
(j) Rotate field rheostat (44) clockwise.
rotating field rheostat (44) counterclockwise. Note on dc
Observe reading on dc voltmeter (13) for polarized relay
voltmeter (13) relay dropout voltage.
pickup voltage.
(h) Place app. switch (23) in CENTER
(k) Rotate
field
rheostat
(44)
position.
counterclockwise.
Observe voltage reading on dc
(i) Place rheostat regulator switch (26)
voltmeter (13) to determine relay dropout voltage.
in RHEOSTAT position putting regulator in control of
(l) Position battery switch (33) in ON
generator voltage.
position.
(j) Rotate rheostat test switch (25) in
(m) Rotate dc voltmeter circuit selector
BATTERY GENERATOR position putting field rheostat
(16) in GEN V position. Using field rheostat (44), adjust
(44) in control of external generator voltage.
generator voltage to within 1/2 volt of the battery
(k) Rotate app. switch (23) in SWITCH
voltage, as measured in paragraph (e) above.
position.
(n) Rotate dc voltmeter circuit selector
(l) Adjust regulator voltage to voltage
(16) -in DIFF. V position. Depress dc voltmeter switch
indicated .in paragraph (g) above, using pile-adjusting
(17).
screws and core-adjusting screw. Rotate regulator
(o) Slowly increase generator voltage
voltage adjusting potentiometer counterclockwise to
decrease voltage and clockwise to increase voltage.
15
