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Sec. 7
Page 126
GM COACH MAINTENANCE MANUAL
R ~
The regulator shown in figure 19 is a heavy-
duty carbon pile regulator developed especially
for use with light weight, high output generators.
Although similar in external appearance to other
heavy-duty regulators of the vibrating-contact type,
the carbon pile regulator functions on an entirely
different principle which must be clearly under-
stood before adjustments of the regulator are at-
tempted. Both types of regulators serve the same
purpose, namely, to limit voltage and current to
the required operating values, and to disconnect
the generator from the battery when the generator
is not capable of supplying power to the system,
but the methods of control are basically different.
CONSTRUCTION
In the carbon pile regulator, the field current
is controlled by a carbon pile rheostat inserted
in the field circuit. The field circuit is not inter -
rupted, and any amount of field current can be
handled provided the unit is made large enough
and has sufficient heat-dissipating capacity.
To
dissipate the heat generated in the rheostat by its
continuous operation, the aluminum castings of
the current and voltage regulators, which hold the
carbon disks, are attached directly to a radiator
which carries the heat outside the box.
The carbon pile rheostat its~Jf consists of a
stack or pile of small flat carbon disks inside a
ceramic tube. Resistance of the stack varies with
the amount of pressure on the disks, decreasing
as the pressure is increased.
The carbon disks
must be absolutely flat and free from any foreign
SYSTEM
VOLTAGE
RHEOSTAT
OVERLOAD RELAY
ACTUATING
RELAY
ND
"\_
FIELD
BATTERY
TP 5595
Figure
19-Carbon Pile Regulator with Cover Removed
material, especially grease and dirt. This is nec-
essary to reduce the change in length of the car-
bon pile in relation to the required changes in
pressure.
Throughout the working range of the
regulator the change in length of the carbon pile
does not exceed .003 inch.
VOLTAGE AND CURRENT REGULATORS
In order to control the generator, the resist-
ance of the rheostat must be made to vary with
every change in load or speed.
This is accom-
plished by the current and voltage regulators in
which the carbon disks are compressed by a
spring and the spring opposed by an electromag-
net.
The electromagnet in the voltage regulator
(fig. 19) is wound with many turns of fine wire
and is connected in shunt across the generator as
shown in figure 20. In the current regulator (fig.
19), the electromagnet is wound with a few turns
of heavy wire and connected in series with the
generator output (fig. 20).
When the voltage or
the current tends to exceed the adjusted value,
the increased pull of the electromagnet reduces
the pressure on the disks, thus increasing their
BATTERY
SYSTEM VOLTAGE
RHEOSTAT
.,_
( fr,
•/•I'-----------,,
VOLTAGE
• - - - - - - - - - - - - ,
L REGULATOR
...
-
,..
-
I
'
-
HUNT
I
-
DING
I
...
,-"
,,-
'
},.J
ELL~4
I
I
I
\
"'
. .
_
ACTUATING
RELAY
CURRENT
REGULATOR
TP 5596
Figure 20-Generator and Regulator Wiring Diagram
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