OT: UPS for FreeBSD

[Erich Dollansky]

Hi,

On Sun, 30 Nov 2014 18:43:09 -0800
perryh at pluto.rain.com (Perry Hutchison) wrote:

> Erich Dollansky <erichsfreebsdlist at alogt.com> wrote:
> > On Sat, 29 Nov 2014 00:49:07 -0800
> > perryh at pluto.rain.com (Perry Hutchison) wrote:
> > > To integrate a UPS with the PSU, one would instead build something
> > > along the lines of:
> > > 
> > >           multitapped
> > > 120VAC ==> step-down ==> 6VAC ==> full-wave ==> ~15VDC ==>
> > > battery1 transformer             rectifier
> > >                   |
> > >                   +---> 3VAC ==> full-wave ==> ~7.5VDC ==>
> > > battery2 rectifier
> > > 
> > > battery1 ==> regulator ==> 12VDC
> > > 
> > > battery2 ==> regulator ==> 5VDC
> >
> > How much energy is then wasted?
> 
> In the transformer and rectifier, very little:  both are highly
> efficient.  The battery will incur charge/discharge losses, but
> we would have to contend with those in any UPS, regardless of
> how the batteries are charged or how their energy is delivered
> to the load.
> 
when developers come to below 10% losses for typical load situations,
they give a party.

> That leaves the regulators.  I'm minimizing those losses by
> providing a separate battery and regulator for each required
> output voltage, so as to minimize the IV loss in the regulator.
> 
> If you prefer the (IMO questionable) relative simplicity of using
> a single (multi-output) regulator, you can certainly use an 18-
> or 24-volt battery and run the regulator(s) off of that to deliver
> 12VDC and 5VDC (or whatever voltages are needed).  The point is
> that it is certainly simpler, and likely more efficient, to deliver
> the DC battery power to the DC load by DC -> DC regulation than by
> inverting to 120 or 240VAC only to have the PC's PSU convert the AC
> right back to DC for the load -- which how external UPS operate.


How do you do a DC-DC regulation without high losses?

The best known way is going via AC to reduce the losses. The moment you
are at AC, the rest does not matter anymore. You can now use standard
AC voltages with standard AC - DC converters to minimise cost. The cost
include here also the operating cost.

Erich