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Powerware 9330 (10 kV A--40 kVA) Installation and Operation
164201300 REV. G 061502
6.2.4 Battery Mode
The UPS transfers to Battery mode automatically if a utility power outage occurs, o r
if the utility po wer does not conform to specified parameters. In Battery mode, the
battery provides emergency DC power that the inverter converts to AC power.
Figure 6---5 shows the path of electrical power through the UPS system when
operating in Battery mode.
CB1
CB2
K1
K5
K3
K2
Open
Closed
Breakers
Contactors
Main Power Flow
Energized
De--Energized
Trickle Current
RECTIFIER
STATIC
SWITCH
BOOST
CONVERTER
INVERTER
BATTERY MODE
CHARGER
BATTERY
MAINTENANCE
BYPASS SWITCH
MAINTENANCE
BYPASS SWITCH
Figure 6---5. Path of Current Through the UPS in Battery Mode
During a utility power failure, the rectifier no longer has an AC utility source in which
to supply the DC output current required to support the battery charger and boost
converter. The input contactor (K1) is opened, the battery charger is turned off , and
battery SCR (Q10) and battery contactor (K2) both receive signals to turn on
enable to supply battery power to the system. Because the battery SCR is an
electronic device, it supplies momentary battery power to the system during the
time it takes the contacts of K2 to close. Energy stored in the battery is supplied
instantaneously to the boost converter so that the inverter and customers load can
be supported without interruption. If the bypass is common with the rectifier input,
the Feed Back Protection contactor (K5) wil l also open. The opening of contactors
K1 and K5 prevent static system voltages from bleeding backwards through the
static switch and rectifier snubber components and re---entering the input source.
While in battery mode, the UPS will enunciate an audible horn, light a visual
indicator lamp on the front panel (System Normal, On Battery), and make an entry
into the alarm event history. A s the battery discharges, the boost converter and
inverter constantly makes minute adjustments enable to maintain a steady output.
The UPS will remain in this operating mode until the input power to the rectifier is
again within the specified voltage or frequency acceptance windows.