requirements will automatically be transferred onto the
equipment consists of a regulated battery charger, a
UPS. Indicator lights at each console will illuminate
battery rack, and a distribution panel.
when the console is operating on UPS. After about 3
You can monitor UPS voltage by using the meters
minutes of operation on UPS, internal supplies will shed
located on the electric plant control console (EPCC) and
noncritical loads within the console.
the battery charger. You can also dial up the UPS battery
The UPS battery charger is interlocked through the
voltage on the demand display indicators (DDIs). The
battery room exhaust ventilation controller. The battery
nominal voltage is 150 volts dc. If this voltage drops
charger will shut down if the ventilation is lost. This is
below 122 volts dc, an alarm will sound at the EPCC.
a necessary safety feature because charging batteries
The EPCC also has an indicator light that illuminates
produce dangerous amounts of hydrogen.
when the battery charger is active. The 150 volts dc is
transformed by dc-to-dc converters to different dc
voltage levels required by the consoles. An inverter
produces 115 volts ac to run each power supply cooling
FFG-7 CLASS SHIPS
fan and for GTE igniter power.
The battery charger maintains a floating charge on
The UPS on the FFG-7 class ship furnishes
the battery bank. With current limited to 30-amperes, a
maximum continuity of service for the propulsion and
discharged battery bank can be recharged within 8
electric plant control system. The UPS is a self-
hours. Realize, however, that the engineering control
contained unit that consists of five major components.
a n d surveillance system (ECSS) does not fully
As shown in figure 2-2, these components are as
discharge the batteries. If the dc bus voltage drops below
follows:
120 volts, the power supplies will shut down. The
battery charger input power is 450 volts ac, 60 hertz
A 120-volt dc to 120-volt ac, 60-Hz inverter
(Hz). It originates from the main switchboard through a
A 120-volt dc battery charger/rectifier
vital propulsion power panel.
Nine lead-acid batteries are mounted in a rack in the
A solid-state automatic load transfer switch
battery room. Eight of the batteries are connected in
Control equipment
series and the ninth battery is a spare. The shelf life of
the spare battery is about 1 year, after which time the
A 120-volt dc battery bank (not in the unit)
battery charger cannot reactivate the battery to full
The UPS is located in the engine room. It is
charge. Special attention should be given to battery
energized from the engine-room lighting panel. Normal
maintenance as the UPS batteries are of special design.
and alternate power from the ship's service
The distribution panel circuit breakers are normally
switchboards is provided by an automatic bus transfer
left closed, and UPS power is available at the console
(ABT). There are 20 6-volt lead-acid storage batteries
power supplies. The console power supplies are located
located in the engine room. The UPS is connected in
in the respective electronics enclosures. When normal
series with the load and is designed to be continuously
ac power is lost at the power supplies, the dc power
Figure 2-2.--Diagram of UPS system for FFG-7 class ships.
2-2
