Re: Smallish CNC Miller

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Blue" <jo001k1132@b...>
wrote:

> Hi Wally,
>
> I'd realised it wouldn't be possible to combine both sides of the

centre-tap

> in its AC form because the phase angles wouldn't be right. I was

going to

> rectify and smooth first then try to add them.
>
> Will that work or am I looking for larger site transformers?
>
> Regards,
>
> Terry
>

You need to build a center tap full wave rectifier. In this
configuration you use the 55-0-55 winding as it is. Basically each
winding conducts 1/2 the time so the current is doubled
automatically. For the voltage you end up with 55 x 1.414 volts out
or 77.8 volts minus 1.4 volts diode voltage drop = 76vdc. A very
simple explanation is here. Notice they are not showing the filter
capacitors. Ground would be the center tap and positive would be
were the 2 diodes connect together. The capacitors would connect to
these plus and ground points.

http://www.allaboutcircuits.com/vol_6/chpt_5/4.html


Wally

>
> > > I'm not sure yet if it is possible to combine both sides of the
> > centre tap
> > > or should I use it as two supplies or 55 volts?
> > >
> > > Regards,
> > >
> > > Terry
> > >
> > > > > No I'm not mistaken. These transformers are centre-tapped

55-0-55.

> > > >
> > > > You're right, I'd forgotten they were centre tapped.
> >
> > If it is a true 55 0 55 transformer with 3 wires only. Then you

can

> > not run the windings in parallel for 55volt double current

operation.

> >
> > In its current configuration each end of a coil is connected to

the

> > other in a series additive configuration.
> >
> >
> > Wally