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 TM 5-685/NAVFAC MO-912
connection of the emergency power source regard-
(2) Static voltage regulators. A static regulator
usually has a static voltage sensor instead of a
less of the condition of the normal power source.
voltage-regulating relay.
c. Service practices. Service practices for transfer
(a) Operation. The voltage sensor output is
switches consist of a complete maintenance pro-
applied to a solid-state or magnetic amplifier and a
gram that is built around records and visual inspec-
discriminator circuit. Signals are thereby provided
tions. The program includes appropriate analysis of
for changing alternator output to raise or lower the
these records.
(1) Record keeping. Equipment and system log
voltage as required. The voltage zone between ini-
sheets are important and necessary functions of
tiation of raising or lowering control action is called
record keeping. The log sheets must be specifically
the voltage band. The band must be more than the
developed to suit auxiliary use.
minimum correction obtainable through the regula-
(2) Troubleshooting. Use recognized industrial
tor or regulator hunting will occur.
(b) Accessories. Accessories include either
practices as the general guide for transfer switch
and systern troubleshooting. Troubleshooting of sys-
thermal delay relays or a resistance capacitance
tem circuits that are not performing according to
network to provide time delay for load trend correc-
specifications and to the required performance level
tion. Time delay retards the signal until accumu-
should be accomplished as follows: refer to engi-
lated time outside the voltage limit, less accumu-
lated time inside the voltage limit, exceeds the time
neering data and drawings pertaining to the par-
delay setting.
ticular plant.
(3) Static exciter regulators. A static exciter
(a) The user should refer to manufacturer's
regulator supplies the alternator field with DC volt-
literature for specific information on individual
age obtained from a three-phase, full wave bridge
transfer switches.
rectifier.
(b) Perform general troubleshooting of the
(a) Operation. A small part of the alterna-
transfer switch if a problem develops. Refer to the
tor's output goes to the regulator which meters the
manufacturer's literature for specific information.
rectified DC voltage back to exciter's field windings.
Usually, all control elements are renewable from
The rectified DC voltage produces a 60 cycle ripple.
the front of the switch without removing the switch
If the ripple gets into the field windings, an electri-
from its enclosures and without removing the main
cal discharge from windings to shaft can occur. A
power cables.
filter can be used to reduce ripple. The discharge is
5-6. Regulators.
caused because copper in the field windings and the
A voltage regulator maintains the terminal voltage
metal shaft act like the plates in a capacitor. This
of an alternator or generator at a predetermined
action may result in shaft and bearing pitting and
value. Voltage is controlled by regulating the
eventual bearing failure. A static exciter is a manu-
strength of the electromagnetic field produced in
factured subassembly, assembled and wired at the
manufacturer's plant, usually using one or more
the alternator exciter. A voltage regulator automati-
silicon rectifiers to convert AC voltage to DC. The
cally overcomes voltage drop within the alternator
subassembly usually includes a regulator and a fil-
by changing field excitation automatically as it var-
ter. Refer to the manufacturer's literature for test
ies with the load.
a. Types of regulators. The types of voltage regu-
and adjustment details.
(b) Accessories. Accessories include either
lators are electromechanical, static voltage, and
thermal delay relays or a resistance capacitance
static exciter.
network to provide time delay for load trend correc-
(1) Electro -mechanical voltage regulators.
tion (refer to para 5-6a(2)(b). A suppressor circuit or
These regulators usually have a servo-control sys-
tem with three principal elements.
ripple filter is usually provided to bypass ripple to
ground before it gets to the generator field.
(a) First is a voltage sensing device with a
b. Service practices. Service practices for voltage
voltage regulating relay. The device monitors the
regulators consist of a complete maintenance pro-
output voltage and sends a signal to the control
gram that is built around records and visual inspec-
circuits.
tions. The program includes appropriate analysis of
(b) Second i s an amplifying section with or
these records.
without time delay, which amplifies the voltage sig-
(1) Record keeping.Equipment and system log
nal.
sheets are important and necessary functions of
(c) Third is a motor drive which responds to
record keeping. The log sheets must be specifically
the signal by moving a tap changer or induction
developed to suit auxiliary use.
regulator in a direction to correct the voltage.
5-15
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