Quantcast Miscellaneous devices

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TM 5-685/NAVFAC MO-912
Table 5-3. Relay troubleshooting-Continued
tery. In addition, batteries provide power for
switchgear control and power to trip some circuit
Note
breakers. Most applications for auxiliary power use
some form of "wet" lead acid battery, however, some
Refer to manufacturer's literature for specific information on
individual equipment.
systems use "dry" nickel cadmium (nicad) batteries.
Both types of batteries produce direct current re-
Cause
Remedy
peatedly by chemical reactions. Batteries must be
Trips at Too Low Temperature
recharged after each use to restore their power. Wet
Wrong heater
Check rating with manufacturer's
cell batteries require scheduled maintenance. This
instruction sheet
includes a visual inspection of all cells, a weekly
Assembled wrong
See manufacturer's instructions
hydrometer reading of the sample cell, and monthly
Relay in high ambient temperature
Install controls closer to each other
readings of floating voltage, water level, hydrom-
or make temperature uniform
eter, and temperature of each cell. Cell connectors
Fails to Reset
must be kept. clean and tight to prevent heating due
Broken mechanism; worn parts;
Replace broken parts, clean and
to high resistance or voltage drop. Tops of cells must
corrosion, dirt
adjust. Install new relay
be kept free of dirt or conductive materials. Charg-
ing area must be exhausted to positively prevent
5-9. Miscellaneous devices.
hydrogen build up and explosion.
Miscellaneous devices include control switches,
d. Surge capacitors. Surge absorbing capacitors
are sometime used, with or without lightning ar-
push buttons, indicating lights, batteries, surge ca-
pacitors, lightning arresters, maintenance tools,
resters, to modify the shape of the surge voltage
test equipment, and fuses.
wave. These capacitors operate at voltages of 240,
480, 600 and higher for single or three-phase opera-
a. Control switches and push buttons. Switchgear
and related control panels contain complete controls
tion. Capacitor banks, formed by individual units
for all functions of the auxiliary generator equip-
connected in parallel, are sometimes used. Fuses
and circuit breakers with time-current characteris-
ment. Control for voltage regulation, phase adjust-
ment, current compensation, engine operating pa-
tics are used to prevent rupture of the capacitor
rameters as well as engine start, stop, and running
case under severe conditions. Safety precautions
speed, battery charging and brightness or dimming
must be observed when working on capacitors.
of indicator lights are usually provided.
(1) Surge capacitors using polychlorinated
b. Indicating lights. White indicating lamps with
biphenyls (PCBs) may still be in use. Refer to 40
colored caps are used to show breaker positions.
CFR 761. Since PCBs are carcinogenic and are not
Green lights indicate open breakers, red lights indi-
biodegradable, some restrictions to their use apply.
cated closed breakers. White lights, when used, are
(2) Special handling is required if PCBs are
energized from potential transformers to indicate
used in any equipment. PCBs are powerful solvents.
live circuits. Some stations include amber or orange
Handling and disposal information and special
lights to indicate that the circuit has been tripped
gloves are available in the base engineer's office.
automatically. Low voltage lamps, connected in se-
e. Lightning arresters. A lightning arrester (a
ries with appropriate resistors, are usually used to
protective device) limits voltage caused by a light-
reduce lamp size and glare. Red and green lights
ning strike and bypasses the related current surge
are usually wired so that they are energized
to a ground system which absorbs most of the strike
through the trip coil of the breaker. An opening in
energy. An overvoltage condition can also be caused
by a fault in the electrical system.
the trip coil circuit is indicated by a dark unlit lamp.
Similar indicating lamps and colored caps are used
(1) There are two general types of arrester
to indicate normal and abnormal conditions for
designs, valve type and expulsion type. The valve
other control functions of the system.
type has one or more sets of spark gaps (series
connected) which establish spark-over voltage, in-
c. Batteries. Storage batteries and battery sys-
tems are frequently a part of an auxiliary power
terrupt the flow of current, and prevent high
system. Batteries are used for prime mover crank-
current flow. The expulsion type has an arc extin-
ing, or an uninterruptible power system. The bat-
guishing chamber in series with the gaps to inter-
teries maintain a charge through the application of
rupt the power frequency current which flows after
the gaps have been sparked over. Design refine-
a "floating" battery charger. As the battery dis-
ments include using oxide film coated components
charges its energy the charger increases its charge
rate by increasing the flow of current into the bat-
and sealing the inner components in a chamber
tery. The converse is true as the battery reaches a
filled with an inert gas. Aluminum cells are used in
full charge, a very small current flows into the bat-
some units.
5-20





 


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