13-14. Carbon-Pile Regulator (Fig. 13-12).
is independent of the action of the regulator. Increasing
the tension of the regulator springs so that the generator
will develop an excessive voltage will send excessive
a. General. In the vibrating-contact type regulator, a
current to the battery, overcharging it. It also will cause
set of contacts open and close to insert and remove a
the generator to overheat, possibly burning it out.
effect, inserts a variable resistance into the field circuit
c. Charging Rate.
that controls the generator. When only a small output is
required, the voltage regulator maintains the resistance
(1) Current Regulator. With the vibrating current
in the field circuit most of the time. When output
regulator, the maximum possible charging current
requirements increase, the resistance is in the field a
remains constant for any one setting of the regulator,
smaller part of the time. This same variable-resistance
regardless of the condition of the battery. To vary this
effect can be achieved by a carbon-pile regulator.
maximum generator output, the spring tension of the
b. Construction. The carbon-pile regulator consists
regulator must be adjusted. The setting must never
essentially of a stack of carbon disks held together by
exceed the rated maximum of the generator.
spring pressure. The spring pressure is applied by an
armature. The resistance through the carbon pile is
(2) Voltage Regulator.
relatively small with full spring pressure applied. But with
less pressure, the resistance increases. The carbon pile
(a) The main advantage of the voltage regulator is that
is connected to the generator field circuit so that its
the output of the generator is controlled to a great extent
resistance is in series with the field. With full pressure
by the amount of charge in the battery. When the
applied, there is no regulation and generator output can
generator reaches a speed at which it develops the
regulated voltage, there will be no further increase in
voltage with increasing speed. The voltage will be
maintained constant at all loads and at all higher speeds.
(b) During the time the generator is connected to the
battery, the difference in voltage between the two is the
voltage available for sending current into the battery. In
a discharged battery, the difference in voltage between
the generator and the battery will be relatively great, so
that a comparatively high charging current will pass from
the generator to the battery. As the charge continues,
the voltage of the battery increases, so that the
difference in voltage between the generator and the
battery is diminishing continually. With a fully charged
battery, the voltage is equal nearly to that of the
generator so that the difference between the two is very
slight. As this slight difference in voltage is all that is
available for sending current into the battery, the
charging current will be small. The charging current,
therefore, is variable and depends upon the charge in the
battery. In practice, the charging current with the
constant voltage regulator varies from a maximum of 25
to 35 amperes for a discharged battery to a minimum of
4 to 6 amperes for a fully charged battery.
Figure 13.12. Carbon-Pile Regulator and