TM 55-2925-236-40
c. Connect the starter generator to the vari-
c. Heating,
Commutation, Minimum Speed an
drive and start the vari-drive.
Equalizing Voltage.
d. Set the main switch to ON.
(1) For heating, commutation, minimum
speed, and equalizing voltage tests, the following
e. Set the VOLTAGE INPUT GENERATOR
AND SUPPLY switch to SUPPLY. The voltage
is considered as a continuous operating condi
indicated is the field voltage applied to the start-
tion: While the starter generator is cold, the re
er generator.
sistance and temperature of the shunt field must
be determined for use in calculating the averag
f. Turn the LINE AMPERE ADJUSTMENT
control to obtain a current reading between 500
field temperature rise used during continuous op
and 800 amperes. The stall torque as indicated
eration at full load. The starter generator is con-
by the stall torque test stand scale, at any point
sidered to have reached its continuous operating
within this 500- to 800-ampere range, must com-
condition when the rate of rise of the shunt field
ply with the values indicated by figure 4-2.
temperature does not increase more than 2F
g. If the specified stall torque cannot be ob-
(1 C) during a five-minute period.
tained within the current range indicated in step
(2) Start the blower and drive motor. In
crease the drive motor speed to operate the start
the correct torque is obtained.
er generator at 8000 rpm. Close suitable switches
h. Set the VOLTAGE INPUT GENERATOR
of the load bank to apply 300 amperes d-c load
AND SUPPLY switch to VOLTAGE INPUT
When the starter generator reaches its continu-
GENERATOR and read and record the starter
ous operating condition as described in step a
generator voltage. The voltage reading should be
proceed as follows:
in accordance with values given in figure 4-2.
(a) Check the readings of the instru-
i. If for any reason the position of end bell
ments. During the heat run, readings must be
assembly (30, figure 31 ) was shifted, allow the
limited to those shown in table 42.
starter generator to run for 1/2 hour and repeat
the test.
8 amperes (max)
Shunt Field
4-5. Dielectric Strength
300 amperes
Load Ammeter
30 volts
Line Voltage
a. Perform this test before any of the final
tests.
b. Using insulation breakdown test set 13700-
terminals D and E on terminal board (49, figure
1C, apply 250 volts, 60 cps for one minute be-
tween each terminal post and the frame
volts.
(ground).
(3) After completing the previous test, de
c. A current. flow of more than 15 milliamperes
crease the speed of the motor until the minimum
indicates insulation breakdown.
rated speed of 4000 rpm is measured on the ta
chometer. Adjust the voltage regulator until a 26-
4-6. Final Tests
volt reading is obtained. The starter generator
a. General. Mount the starter generator on the
must deliver rated current of 300 amperes, as
test stand, as described in paragraph 4-1a(4).
read on the ammeter.
b. Maximum Speed for Regulation.
Note. At no time during the above heat runs
should the required resistance external to the shunt field
an operational warm-up prior to this test.
be less than 1.25 ohms. Refer to paragraph 4-6b t o
calculate the external shunt field resistance.
(1) Turn on the test stand controls and in-
(4) Readjust the regulator until a 30-volt
crease the drive motor speed to 10,000 rpm.
reading is obtained.
(2) Adjust the regulator until the output
voltage is 30 volts.
d. Commutation. Immediately following the
previous heat runs, with the starter generator
(3) Record the field voltage (Ef) and field
hot, observe the commutation of the starter gen-
current (If ).
erator over the speed range 4400 to 8000 rpm
(4) Calculate the external resistance in the
for no load (all load switches off), half load
field circuit by dividing the field voltage by the
field current.
(suitable load switches turned onto give 150 am-
(5) The external resistance in the shunt
peres), and rated load (suitable switches turned
field must not exceed 35 ohms.
4-3
