UPS for FreeBSD

[Alejandro Imass]

On Mon, Dec 1, 2014 at 9:38 PM, Erich Dollansky <erichsfreebsdlist at alogt.com
> wrote:

> Hi,
>
> On Mon, 1 Dec 2014 12:39:24 -0500
> Alejandro Imass <aimass at yabarana.com> wrote:
>
> > On Sun, Nov 30, 2014 at 12:33 AM, John Johnstone
> > <jjohnstone at tridentusa.com> wrote:
> >
>
>
[...]


> the average volage over a square is much higher than over a sine. If
> the components are not designed for this, they will fail. You can see
> this effect by connecting a light bulb to an UPS and switch mains off
> an on again. The smaller the difference in brightness gets, the better
> the UPS emulates a sine. Of course, the life time of the light bulb
> gets reduced.
>
>
Should not be a problem for any modern switching power supply. In fact the
higher the RMS the more efficient it will operate. The RMS of the sine
x/SQRT(2) of a square wave is just x, where x is the peak to peak voltage.
The peak to peak of 120V is around 170V which is just fine for most
switching power supplies which are rated for about 250V RMS. It _could_ be
a bit of a problem is the UPS is for 240V but I have never personally seen
one in a North American store. Besides any 240V UPS manufacturer would have
to know this and honestly I don't really think that any UPS uses a square
wave.

I will be sure to test this with an oscilloscope when I finally buy the UPS
that started this thread - I promise I will buy the cheapest one I find and
post pictures of the output waveform ;-)

[...]


> This is the question. Most power supplies will be able to handle the
> square waveform. Escpecially modern power supplies being able to handle
> any voltage from 100 to 250V.
>
>
Actually I was referring to another comment that suggested that HF
harmonics from saw-tooth emulation or square wave "ring" could somehow
affect the switching PS of a typical computer. I think this is unlikely
because it will get filtered by the first rectification circuitry of the
switching power supply (I am no expert and could be wrong and maybe some
switching PS would be sensitive to this, but I really doubt it). HF does
affect some transformers and linear equipment and still is very unlikely.

[..]


> It is the volume. When the cheaper UPSes appeared, their price
> advantage was pretty minor.
>
> I wonder meanwhile if it is not cheaper to use an inverter used in
> solar panel installations. At least for larger inverters, they have a
> clear price advantage but require batteries which are not available at
> the next corner shop.
>

The problem I think is the switch-over speed. It would be really cool to
find UPS that use *any* external battery, and you could just use a car
battery for example which is very reliable, durable and readily available.

Best,
-- 
Alejandro Imass