controller are also protected. However, sometimes
source for console power. The DD-963,
short circuit protection is provided in the
DDG-993, and CG-47 class ships use a slightly
different concept for supplying uninterrupted
controller. This is done in cases where it is not
power to consoles. On these ships the normal
otherwise provided by the power distribution
supply of power is from the ship's service 120-volt
system. Short circuit protection for control
circuits is provided by fuses in the controller
ac, 60-Hz bus. Power is also fed to the electronics
enclosure.
from the 150-volt dc UPS battery bank. All
switching for this system is done in the propulsion
electronics. These classes also have battery backup
for each SWBD and SSGTGs. The battery supply
UNINTERRUPTIBLE
POWER SUPPLY
is an uninterruptible system but is NOT commonly
referred to as UPS.
Periodically a gas turbine ship experiences a
partial or total loss of 60-Hz ship's service power
to engineering equipment requiring a constant
LEAD-ACID STORAGE BATTERIES
power source. The equipment may be a control
console, a SWBD, or a GTE. Most control
Storage batteries provide the power source for
consoles cannot withstand an interruption of the
the UPS system. Periodic inspection of the storage
power that feeds them. The LM2500 will shut
battery is essential in maintaining maximum
down if power is removed from the fuel valve
efficiency and long life of the battery. Batteries
solenoids. Therefore, these vital engineering
used for UPS systems are subjected to moderately
functions must be maintained during a power
heavy use. They require frequent charging by the
interruption.
UPS battery charger.
To provide power for vital pieces of equipment
As a GSE/GSM, you will be required to main-
during short-term operation, gas turbine ships are
tain these battery banks. All the batteries used in
designed with battery backup systems. This
UPS systems are wet-cell types. Their maintenance
battery backup provides an alternate source of
requirements are special. For more information
power upon failure of ship's service power.
on battery construction and their principles of
Because these systems need an immediate standby
operation, refer to NEETS, module 1.
source of power, they must have a very rapid
method of transferring the load to the backup.
This is done by use of static (electronic) switching.
The shift from failing 60-Hz power to the battery
SUMMARY
backup is very rapid. It is an uninterrupted
shift. Therefore, the battery backup system is
In this chapter we have discussed the major
commonly known as an uninterruptible power
components of an ac electrical system. These
supply (UPS).
included generators and motors, 60-Hz distribu-
All propulsion electronics rely on 115/120-volt
tion system components, the UPS, and lead-acid
ac as the input to their power supplies. The UPS
storage batteries. You must remember that
battery systems for these consoles must provide
there are many different types of systems
and components other than the ones we have
power in that range. Batteries are normally a low-
voltage dc power source. This means several
discussed. Also, you should not undertake work
batteries must be placed in series to obtain the
on electrical equipment without reference to the
proper voltage levels. We will refer to this group
proper technical manual.
of batteries as a battery bank.
For additional information on the material
covered in this chapter, refer to Naval Ships'
The UPS system is different on the FFG-7
class ships and the twin-shaft gas turbine ships.
Technical Manual, chapter 300, "Electrical Plant
The UPS used on the FFG-7 class ship is the
General," chapter 310, "Electrical Power
normal source of power for the propulsion
Generators and Conversion Equipment," and
electronics. It does not employ the batteries all
chapter 320, "Electrical Power Distribution
the time, but the UPS equipment is the normal
System."
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