OT: UPS for FreeBSD

RW rwmaillists at googlemail.com
Sun Nov 30 21:03:12 UTC 2014

On Sun, 30 Nov 2014 11:31:31 -0800
Darren Pilgrim wrote:

> On 11/29/2014 3:12 PM, Perry Hutchison wrote:
> > Presuming a reasonable amount of capacitance on the output,
> > a half wave (single diode) rectifier should produce a DC
> > output roughly equal to the peak value of the AC input,
> > which is indeed ~1.4 * the RMS AC voltage.  A two-diode
> > full-wave rectifier using a center tap will also produce DC
> > of ~1.4 * the RMS voltage of the entire winding (and with
> > the advantage of less ripple).
> >
> > However, a full wave bridge (4 diodes) should produce a DC
> > output roughly equal to the peak-to-peak value of the AC
> > input, or ~2.8 * the RMS voltage.
> An unloaded, ideal, single-phase FWR produces Vdc = 0.900Vrms.  The 
> factor is 2sqrt(2)/pi, to be precise.  A half-wave rectifier produces 
> half that.

That's the mean voltage, which is of limited relevance.

>  From where did you get your figures?

He's referring to a rectifier charging a smoothing capacitor; the
voltage will rise to sqrt(2)*Vrms. He's added on an unnecessary  factor
of two - possibly because he's mixing it up with a bridge-rectifier in a
centre-tap configuration. 

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