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48 Reserve power
UPS
sizing
Since power distribution for AC systems is provided on a per-column basis,
partial system backup is available for all system options, thus reducing
reserve power requirements. In other words, it is possible to back up all of the
common equipment, but only a portion of the peripheral equipment, reducing
both UPS and battery costs.
Even
if it is desired to back up the entire system, the per-column powering
allows the choice of provisioning one UPS per column, one UPS for the entire
system (all columns), or any combination.
In order to determine the
siie
of UPS needed, the total system (or column)
power requirements are first determined as in the previous section “Operating
power requirements.” The real power in Watts (W) is then converted to
complex or “apparent” power in Volt-Amps (VA) by dividing the real power
by the typical system power factor of 0.6. The UPS is then sized in terms of
its rating in VA (or kVA).
.
The sizing and provisioning of the UPS batteries will be determined by
following the specific instructions provided by the manufacturer of the UPS
that has been selected. The general approach, however, is to take the total
system power in Watts, divide by the UPS inverter efficiency, and convert to
battery current drain by dividing by the nominal discharge voltage of the
__
battery string. The battery current drain is then multiplied by the time that is
needed for the reserve power to operate to determine the battery requirements
in Amp-hours (A-hrs).
Recommended UPS vendors and models
As of the publication date of this document, the following UPS systems have
been tested by Northern Telecom and verified to work with the SL-1 system.
These vendors and models meet high standards of both quality and
functionality and are recommended to be used with the SL-1.
This list may change at any time in the future. Other UPS vendors may have
products which work fine with SL-1 systems, and the vendors listed here may
have other models and sizes that are also suitable. In particular, there are UPS
systems larger than 10
kVA
available that could be used with some of the
larger system option 71 configurations.
Power engineering
553-3001-152
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