Regulation of Generator Output
The fields of the generator depend upon the current
from the armature of the generator for magnetization.
Because the current developed by the generator
increases in direct proportion to its speed, the fields
become stronger as the speed increases and,
correspondingly, the armature generates more current.
The extreme variations in speed of the automotive
engine make it necessary to regulate output of the
generator to prevent excessive current or voltage
overload. On the average unit of CESE, a charging
current in excess of 12 to 15 amperes is harmful to a
fully charged battery if continued for too long.
Regulators are of two types, functioning to
regulate either voltage or current. The voltage
regulator regulates the voltage in the electric system
and prevents excessive voltage, which can cause
damage to the electric units and overcharge the battery.
The current regulator is a current limiter; it prevents
the generator output from increasing beyond the rated
output of the generator.
Regulation of voltage only might be satisfactory
from the standpoint of the battery; however, if the
battery were badly discharged or if a heavy electrical
load were connected, the heavy current might overload
itself to supply the heavy current demand. Therefore,
both current and voltage controls are used in a charging
In most applications, a regulator assembly consists
of a cutout relay, current regulator, and voltage
regulator (fig. 2-13). Each unit contains a separate
core, coil, and set of contacts. The regulator assembly
provides full control of the shunt-type generator under
all conditions. Either the current regulator or the
voltage regulator may be operating at any one time, but
in no case do they both operate at the same time.
When the electric load requirements are high and
the battery is low, the current regulator will operate to
prevent the generator output from exceeding its safe
maximum. In this case, the voltage is not sufficient to
cause the voltage regulator to operate. But if the load
requirements are reduced or the battery begins to come
up to charge, the line voltage will increase to a value
sufficient to cause the voltage regulator to operate.
When this happens, the generator output is reduced; it
is no longer sufficiently high to cause the current
regulator to operate. All regulation is then dependent
on the voltage regulator. Figure 2-14 shows a
schematic wiring diagram of a typical dc charging
circuit. In this circuit, two resistances are connected in
Figure 2-13.Regulator assembly with cover removed.
parallel into the generator field circuit when the current
regulator points open. This provides a low value of
resistance, which is sufficient to prevent the generator
output from exceeding its safe maximum. When the
voltage regulator contact points open, only one
resistance is inserted into the generator field circuit,
and this provides a higher value of resistance. The
voltage regulator must employ a higher resistance
because it must reduce the generator output as it
operates, and it requires more resistance to reduce the
output than merely to prevent the output from going
beyond the safe maximum of the generator.
For some special applications, you may find a
combined current-voltage regulator. In this case, the
regulators are combined in a single unit. The regulator
assembly will consist of two (regulator and circuit
breaker) instead of three units.
The regulators just described are known as
electromagnetic vibrating-contact regulators. The
points on the armatures of the regulators may open and
close as many as 300 times in one second to achieve the
The transistor type regulator is being used in late
model equipment. This regulator has no moving parts.
It consists of transistors, diodes, condensers, and
resistors. Some models have two filter condensers,
while others have only one.
Adjustments are provided on some types of
regulators and should be made only with the use of the
manufacturers instructions and the recommended
testing equipment. TRIAL AND ERROR METHOD
OF REPAIR WILL NOT WORK.