Re: System Saver IIgs -- ID of burned part?-- line protection

["Keith Olson" <s p a m t r a p 0 0 7 @ y a h o o . c o m>]

[comments inline]


"Rubywand" <rubywand@swbell.net> wrote in message
3B39D378.A133B669@swbell.net">news:3B39D378.A133B669@swbell.net...

-----8<-----

> >   UPSes, especially the sub $200 version connect your computer direct to
AC mains
> > when not in battery backup mode.  That UPS relay is 1000 times too slow
to afford any
> > surge protection.
>
>      What you call a "surge" is often referred to as a "spike".
>
>      UPS's work fine as protection against relatively long duration
> over/under voltage situations. This, in turn, works to protect against
> spiking. Spikes are more likely during sustained off-voltage (high or low)
> situations. Just being taken off-line and placed on inverter power for a
few
> seconds prevents exposure to especially dangerous spikes.
>
>
> > Furthermore, destructive surges are common mode transients.
>
>      Which, really, is very fortunate.
>
>
>
> > They pass right through UPSes sometimes
> > without ever being seen by the UPS.  Understand the difference
> > between common vs differential mode surges.  It is why UPSes are so
> > stingy with detailed specs.  Look at these for a better line UPS.
Notice on page 5 -
> > no common mode surge protection!:
> >      http://www.apcmedia.com/litpdfs/pdfs_new/996%2D0383e.pdf

One minor (or not so minor) point:  a *true* UPS (~U~ninterruptable ~P~ower
~S~upply) contains two separate circuits - a charger, and an invertor.  When
line voltage is lost, the invertor is not effected at all.  It simply keeps
on doing what it always did. (i.e. converting DC from the battery to AC)
This separation also provides buffering from overvoltages and brownouts.
Even a power surge that totally blows out the charger might not kill the
battery, thus allowing you time to shut everything down.

What many companies advertise as a 'UPS' (notice the quotes) is actually an
SPS (~S~tandby ~P~ower ~S~upply), which provides (generally) unfiltered AC
power straight from the line while keeping a backup battery topped up.  When
power is lost, an invertor kicks in to provide power.  While both circuits
use a charger & invertor combo, it doesn't take a genius to notice that an
SPS doesn't need components that are as robust, as they are only needed once
in a while, instead of constantly, as is the case with a USP.  This explains
why a UPS can cost twice as much as an equivalent SPS.  If you want to know
if you are getting a true UPS, just ask the salesman what the switching time
is.  If he gives you any answer other than 'none', ask him if he even knows
the difference between a UPS and an SPS.....gently.

Hope this helps
Keith Olson