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The
most frequently-used technology for protecting PCs in an environment
with little electrical interference.
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The
PC is normally powered from the EDF mains supply with no power
conversion. Its operating principle is sequential (on mains/on
battery). If there is a power failure, or a drop or increase in
voltage, the UPS takes power from its battery to provide a stabilized
power source. Off-line technology is not suitable for use if there
are frequent disturbances (industrial or rural environments).
Advantages: low cost.
Drawbacks: the application is affected by all current fluctuations
outside accepted tolerance limits.
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Mid-range
technology, for protecting single station servers.
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It
operates in the same way as an Off-line UPS. The UPS uses microprocessor
control, monitoring the quality of the mains supply and responding
to changes. A booster, (voltage compensation circuit), is activated
in the event of an extended dip in voltage. Line interactive technology,
as with off-line, is not suitable above 2 KVA.
Advantages: it can alleviate extended drops in voltage.
Drawbacks: it does not provide complete protection.
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Top
of the range technology, for centralized protection of servers,
to guarantee a constant quality of supply, whatever the fluctuations
on the mains.
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The
On-line UPS only uses its batteries in the event of a power cut:
the current is fully equalized by transforming the AC to DC, then
back to AC again. This continuous double conversion process reduces
the effect of any electrical disturbances which could damage a
computer, thus providing fail-safe protection. It is essential
to protect installations which are critical to the business, and
to provide continuous protection.
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