system which will register on the dc
tem. When using the 40-ohm or the 250-ohm
f i e l d current rheostat (52 and 55, fig. 16) to
correct ampere output reading is indi-
control the output of the generator having no
cated on the load dc ammeter (1) with
g e n e r a t o r regulator connected in the system,
t h e correct time interval set on the
battery charge timer (46) b(1) ( d )
t h e generator field external-internal ground
switch (51, fig. 16) must be placed in either the
and (e) above,
(see
manufacturer's
s p e c i f i c a t i o n and/or TM 9-6140-200-
"EXT-GND" or "INT-GND" position, depend-
ing upon the system under test, a a b o v e .
15). Turn off and disconnect the bat-
tery charge circuit and replace bat-
c. Generator. Regulator used in the System.
t e r i e s in the battery compartment as
When a generator regulator is used in the sys-
prescribed in b(1) (h) a b o v e .
tem under test to control the output of the gen-
(3) 24-Volt battery charging procedures.
erator, the generator regulator itself will com-
The procedures for charging the 24-
plete the field circuit and provide the correct
volt battery system of the test stand is
ground for the system. In this hook-up the
the same as prescribed in b(1) above,
generator field external-internal ground switch
e x c e p t the voltage selector switch
(51, fig. 16) is not required and is placed in the
(41-A) is set in the "24V" position,
c e n t e r "OFF" position.
Note. Attach the leads from the generator to the
test stand in the same manner for either external-
(22) in the "50V (X5)" position, and
ground field or internal-ground field.
t h e battery charge circuit variable
control (47) is adjusted until approxi-
d. Polarizing Methods for Internal and Ex-
m a t e l y 2 volts reading is indicated
ternal Ground Field Generator.
below the 24 volt rating of the battery
(1) G e n e r a l . After a generator has been
system which will register on the dc
repaired and reinstalled on a vehicle
or at any time before or after a gen-
correct ampere output reading is indi-
erator has been tested, it must be de-
cated on the load dc ammeter (1) with
polarized to make sure that it has the
t h e correct time interval set on the
c o r r e c t polarity with respect to the
battery charge timer (46) b(1) ( d )
battery it is to charge or to have the
a n d (e) a b o v e , ( s e e m a n u f a c t u r e r ' s
c o r r e c t polarity to perform tests on
specifications and/or TM 9-4910-200-
t h e generator. Failure to depolarize
15). Turn off and disconnect the bat-
t h e generator may result in burned
tery charge circuit and replace the bat-
relay contact points, a run-down bat-
t e r i e s in the battery compartment as
t e r y and possibly serious damage to
prescribed in b(1) (h) a b o v e .
t h e generator itself when assembled
on the vehicle or incorrect test results
99. Testing and Polarizing Internal-Ground
when testing it on the test stand. The
Field and External-Ground Field Gener-
procedure to follow in correcting
g e n e r a t o r polarity depends upon the
a. General. The generator regulators of au-
g e n e r a t o r - r e g u l a t o r wiring circuits-
t o m o t i v e generators are either standard-duty
that is, whether the generator field is
or heavy-duty. The difference between the two
i n t e r n a l l y grounded or is grounded
systems is the method of grounding the field
through the regulator (externally
grounded).
d u t y generator regulators, the generator field
(2) Polarizing
internal
and
c o i l is externally grounded, whereas, in the
external
ground field generators using battery
h e a v y - d u t y generator regulator, the generator
current of vehicle.
field coil is internally grounded. For details for
(a) Internal ground field type (heavy
preparing the test stand for these two types of
grounded generators and for polarizing instruc-
tions refer to b through d b e l o w .
generator regulator on the vehicle