pfarrell;566448 Wrote: 
> ... there are different types of UPS designs. The 
> cheap ones switch "quickly", the better ones are called "line 
> interactive" and always charge the battery and always run off the 
> battery (not the mains).
ItÂ’s rather easily to know which UPS is which.  To have line
interactive and 'clean' power, then UPS costs $500, $1000, or more. 
Most all UPSes are switches.   Since a UPS is intended for electronics,
that 'cheapest solution'  is more than sufficient. Anything a UPS might
do is already done better inside electronic appliances.  

And 'protection' provided by a line interactive UPS is already inside
every electronic power supply.  If that UPS AC to DC to AC conversion
supplies protection, then the AC to DC to AC to DC again protection
inside every electronics appliance is superior.   The UPS does not have
1000 volts galvanic isolation.  Computers do.  Intel requirements demand
that computer supplies be superior to other electronics appliances.

All electronics already contains significant protection.  Therefore 
additional protection is only for direct lightning strikes.  Surges
that typically occur once every seven years.

Any protection a UPS might do is already inside the computer.  Why
is a UPS output (in battery backup mode) so 'dirty'?  Why does a
typical 120 volts UPS output 200 volt square waves with spikes up to
270 volts between those square waves?  Because all electronics -
especially computers - are so robust.  Makes 'dirty' UPS electricity
irrelevant.

Most all UPSes connect the appliance directly to AC mains when not in
battery backup mode.  They will do most anything to keep you confused.
Many foolishly believe its AC power is generated from DC.  Nonsense. 
Put a scope on the UPS output.   When is its output cleanest?  When the
relay connects the appliance directly to AC mains.  Anything a
manufacturer can do to subvert knowledge gets the naive to claim a UPS
'cleans' electricity.  Any urban myth that increases sales is a good
thing.

A Linux box (properly assembled) should recover harmlessly from
unexpected power loss.


-- 
westom
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