When used on dc generators, voltage regulators and
generator output voltage to the ac voltage regulator. You
their auxiliary equipment maintain the generator
should also note that a portion of the exciter's armature
terminal voltage within specified limits. They also
output is connected through the exciter's field rheostat
provide proper division of the load between generators
(Rx) then through the exciter shunt field windings and
operating in parallel.
finally back to the exciter armature. Obviously, the
When used on ac generators, voltage regulators
exciter supplies direct current to its own control field, in
and their auxiliary equipment function to maintain
addition to the ac generator field, as determined by the
the generator terminal voltage within specified
setting of Rx. The setting of Rx is controlled by the
limits. They also provide proper division of the
magnetic strength of the control coil (L). The magnetic
reactive current between generators operating in
strength of L is controlled by the voltage across the
parallel.
resistor (R). The voltage across R is rectified dc and is
The types of voltage regulators used in naval vessels
proportional to the ac line voltage. (Rectifiers are
are
devices that change ac to dc.)
1. the indirect acting rheostatic,
Thus, the essential function of the voltage regulator
is to use the ac output voltage, which it is designed to
2. the direct acting rheostatic,
control, as a sensing influence to control the amount of
3. the rotary amplifier, and
current felt by the rotor field windings. A drop in the
4. the combined static excitation and voltage
output ac voltage will change the setting of Rx in one
regulation system.
direction and cause a rise in the excitation to the field
One voltage regulator is provided for each generator
windings.
to be regulated. In some ship's service. installations a
spare voltage-sensitive (control) element is installed on
Conversely, an increase in the output ac voltage
the switchboard. The switchboard is provided with a
will change the setting of Rx in the opposite
transfer switch. This allows the spare element to be
direction and cause a drop in the excitation to the field
placed in service if either of the other control elements
windings. These latter two characteristics are caused by
become disarranged. Spare control elements are not
installed for voltage regulators used on emergency
These
actions within the voltage regulator.
generators.
characteristics are common to both the resistive and
magnetic (magnetic amplifier) types of ac voltage
regulators. Both types of regulators perform the same
INDIRECT-ACTING RHEOSTATIC
functions, but accomplish them through different
VOLTAGE REGULATOR
operating principles.
The indirect-acting rheostatic type of voltage
regulators were used on all ac ship's service
generators and many emergency generators until
TYPES OF VOLTAGE
1943. Very few of these voltage regulators are still in
REGULATORS
service; therefore, they aren't discussed in this
TRAMAN.
A voltage regulator consists of a control element and
associated mechanical or electrical means to produce
the changes in the generator field current that are
DIRECT-ACTING RHEOSTAT
necessary to maintain a predetermined constant
VOLTAGE REGULATOR
generator terminal voltage. These changes are
necessary to maintain a predetermined constant
Direct-acting rheostatic voltage regulators consist
generator terminal voltage and to provide for proper
of a control element in the form of a regulator coil that
division of the reactive current between generators
exerts a mechanical force directly on a special type of
regulating resistance.
operating in parallel.
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