b. Connect the negative terminal of the bat-
a. Temperature. Since the dc generator is self-
tely to terminal E on the terminal board.
cooled, no cooling air is required. Check that the
c. Apply battely current to the shunt field for
ambient temperature is77 27F (25 15C ).
5 seconds by closing the knife switch.
b. Direction of Rotation. Drive the dc gener-
d. Repeat the operation several times to be
ator in a counterclockwise direction, as viewed
sure that the field is properly flashed.
from the drive end, during all tests.
c. Plastic Windows. It is recommended that a
transparent plastic window strap be used during
Use a knife switch when flashing the
the brush seating procedure, so that the commu-
field. Opening the circuit at the starter
tator end brushes will be visible. A spare brush
generator or battery terminals can re-
access cover can be modified in the shop by cut-
ting out squares, and riveting transparent nom-
sult in severe damage to the terminals
or explosion of the battery.
flammable plastic window panes in place on the
Remove the brush access cover and replace
Do not operate the dc generator without
it with the plastic window strap. (Refer to para-
the brush access cover in place, as over-
graph 4-1a(3). The brush "run-in" can now be
b. Operate the
at 5000 rpm until
d. Mounting. The dc generator should be
the face of each brush contacts the commutator
mounted on aircraft generator test stand 7199-1
100 percent in the direction of rotation and for
at least 75 percent of brush dimension parallel
of driving the generator at speeds form 5000 to
11,000 rpm. The longitudinal axis of the gener-
evidence of excessive grooving or other surface
ator should be horizontal.
damage to the face of the brush.
e. Excitation. The dc genernator should be self-
excited and controlled by a suitable variable re-
sistance in series with the shunt f ield.
The shunt field current should not be consid-
ered as part of the dc generator load current.
f. Load Location. The load for the dc gener-
ator should be located so that it will not affect
the ambient or blast cooling air temperature.
g. Warm-Up. The dc generator should be op-
erated at a continuous operating speed, deliver-
ing the rated load at the rated voltage to obtain
a constant temperature.
h. Output Voltage Measurements. Measure
output voltages between terminals E and B.
i. Shunt Field Voltage. Measure the voltage
drop across the shunt field between terminals A
To be sure that the dc magnetic circuit retains
c. There must be
no sparking except for fine
enough residual residual, to allow the dc gen-
at the generator brushes.
erator voltage to build up properly, flash the
Brushes should be
removed from their brush
field as described in steps a through d, below.
holders for periodic
a. Connect the positive terminal of a 12-volt
battery through a single-pole, single-throw knife
If the brushes are removed from the brush
holders, be sure to return each brush to the
holder from which it was removed.