Re: [CAD_CAM_EDM_DRO] Re: toroid transformer - back to basics

Thanks a bunch!! So $25 for one of these is a good deal?
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Thomas Powell (VMOA 741)
1994 NOS injected T-Boost sales
Tourmaster V-Max Clear clutch cover sales
"LAFGAS" Handlebar brackets
Contact me at: tppjr@...
http://imageevent.com/tppjr (photopage)
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----- Original Message -----
From: "Antonius J.M. Groothuizen" <agroot@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, October 01, 2003 4:34 PM
Subject: [CAD_CAM_EDM_DRO] Re: toroid transformer - back to basics


>
> The original specifications for the transformer were:
>
> 115/230 Volt, 50/60Hz Output: 20 VAC @ 10 AAC 118 VAC @ 13 AAC
>
> Let's let W1 represent the primary, W2 the 118V secondary, and W3 the
> 20V secondary. An aspect to note about transformers is that any
> winding or combination of windings can be used as the primary. Here
> we have three separate windings, one known to be center tapped.
>
> Going back to basic transformer theory, the voltage ratio is
> equivalent to the turns ratio of the transformer.
>
> W1 : W2 : W3 = 230 : 118 : 20
>
> If we put windings one and three in series, using it as the 'primary'
> our turns ratio becomes:
>
> (230 + 20) : 118
>
> = 250:118
>
> Pumping 115 VAC into this 'primary' yields an output at W2 of
>
> 118 * 115VAC / 250 = 54.28 VAC
>
> Multiply by 1.4 to get the DC equivalent
>
> =76 V
>
> Subtract diode losses
>
> yields approximately 75 VDC
>
>
> Now lets check the current.
>
> Primary power - losses = secondary power
>
> Assuming zero losses, and substituting with original values
>
> V1 * I1 = (V2 * I2) + (V3 * I3)
> I1 = ((118 * 13) + (20 * 10)) / 230
> I1 = 7.54A
>
> We'll use this as the maximum current for our joined winding primary
> as it is the lesser of the two current ratings and compute our
> secondary current.
>
> I2 = (V1 * I1) / V2
> I2 = 115 * 7.54 / 54.28
> I2 = 15.97
>
> We note that this is more than the rating of our secondary, meaning
> that we can safely draw the rated 13 amps from this configuration,
> and recompute our primary current.
>
> I1 = (V2 * I2) / V1
> I1 = (54.28 * 13) /115
> I1 = 6.14 Amps
>
> The conclusion is that by connecting the full primary, and the 20 V
> secondary in series we can use this transformer to build a DC power
> supply with an output rating about 75V 13A.
>
> Tony
>
>
>
>
>
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <davemucha@j...> wrote:
> >
> > > >
> > > > Interesting idea.
> > > >
> > > > does running them out of phase effect the current of the
> > output ?
> > > > would it be the same as the the higher voltage rating or
> changed
> > > by
> > > > the lower one ?
> > > >
> > > > Also, is the input current effected by this ?
> > > >
> > > > Dave
> > >
> > >
> > > Dave,
> > >
> > > I'm not sure how this will affect the input current. My guess
> would
> > > be it doesnt but i'm not sure. I mean there is no current flowing
> > > due to them being out of phase.
> > >
> > > The current would be limited by whatever tap has the lower rating.
> > >
> > >
> > > Thomas,
> > >
> > > I'm not sure what voltage your looking for but if you plan on
> > > running geckos then 220 will not be an option. 110 is be redily
> > > available so its no big deal. The DC voltage obtained is roughly
> > > 1.41 (root 2) times the AC voltage.
> > >
> > > Mark
> >
> > too far removed.....
> >
> > If one puts 110 on the 220 line, that drops the 118 to 59vac.
> > Therfore, 59 less 1.4 for the rectifier drop = 57.6 VAC, with the
> > filer cap, 57.6 VAC x 1.414 you jump to 81.4 VDC not too bad.
> >
> > A couple of diodes and it's under 80V, use the second secondary to
> > drop the first secondary ? not sure exactly how that works, but if
> > it does, then great.
> >
> > Dave
>
>
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