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4200FA CT
January 13, 2004
3
H. Input / Output EMI / RFI Filters
2.3 System Operation
The UPS shall operate as an on-line, fully automatic system in the
following modes:
A. NORMAL - Incoming AC power is boosted using a chopper circuit,
and converted into DC power. The DC power is then used to charge the
battery bank while at the same time providing clean, DC power to the
inverter circuitry. The inverter converts DC power to regulated AC power
which feeds the load.
B. EMERGENCY - Upon failure of commercial AC power, the UPS shall
derive power from the battery bank and continue feeding the load with
clean, regulated AC power. There is no interruption to the critical load
upon failure or restoration of commercial AC power.
C. RECHARGE - Upon restoration of the commercial AC source, the
rectifier/chopper powers the inverter while simultaneously recharging the
battery bank. The UPS shall have the following recharge process:
a) a constant level of current is used to recharge the batteries (the
process shall utilize a current-limit function to prevent overcharging
batteries, thus extending the life of the batteries)
b) as the batteries reach the normal charge level, a constant-voltage
control shall begin which causes the battery recharge current to
gradually decrease
c) Under normal operation, the UPS battery bank "floats" at the 2.25-2.27
volts per cell DC level to stay fully charged and ready for the next
discharge.
D. BYPASS MODE - Upon detection of an internal fault or output
overload, the UPS shall automatically switch from inverter power to an
internal bypass via the static switch. Transfer shall be within 4
milliseconds, causing no interruption to the critical load. While in bypass,
the UPS shall protect against spikes and common/normal mode noise by
utilizing a dual-winding output isolation transformer. “Return from Bypass
mode” shall be an automatic function, without interruption to the critical
load. Transfer to Bypass may also be performed as a manual operation
via the UPS front panel.
E. POWER CONDITIONING MODE - Should the batteries be removed
from the UPS, the UPS shall continue to function and still provide