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 UPS units are designed to provide power to your equipment in the event of loss of mains supply. They sit between the mains and your equipment, and contain batteries that are kept charged from the mains supply. In the event of loss of mains power, the unit supplies power from the batteries.
Obviously there is a limit to the amount of power stored
in the batteries, and so the two things which determine how long the power will
last for are the current draw of your equipment and the capacity of the
batteries.
When choosing a UPS for Computer systems, several additional issues arise.
Because the cost of UPS units increases with their capacity, a unit is often
chosen to provide the minimum run time that will allow an orderly shutdown of
the equipment. This is because the computer's data is usually considered
to be more important than continued access. Dropping the power to the
computer when it is in the middle of processing can have catastrophic data and
hardware results. To help with this, Emerson UPS units have the ability to
send a message to the computer when battery power is running out to tell it to
shut down in a controlled manner. This communication takes place using a
cable or via a network, and works with software (provided with the unit) that
runs on the PC or server.
There are three methods used by Emerson UPS units to maintain power.
The first, called
Offline, monitors the mains power, and if this is
interrupted, automatically changes over to the battery power in a fraction of a
second. The second method, known as
Line-Interactive, works in the same way,
but also conditions the mains power to correct voltage fluctuations. The
third type,
Online units, provide power from batteries all the time, and
use the mains power to keep the batteries charged. As a result, if the
mains supply fails, there is no delay in switching to battery power.
Emerson Network Power make UPS ranges of each type to suit
different requirements and budgets. Liebert, a famous name in the UPS arena, is part of the Emerson Network Power group, and so UPS ranges may be branded as Liebert or Emerson. For more information on UPS operation, please select from the Liebert 'white paper' links below: "All UPSs Are Not Created Equal" User Needs Drive Successful UPS Selection
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How
UPS units work
