Re: supplying power to a color vector monitor

An autotransformer does NOT isolate. For example, an autotransformer
that converts 220 volts to 120 volts has only one winding (220 volts)
WITH A TAP at 120 volts. The advantage of not having an isolated
winding is that there is more room in a given size transformer to allow
a heavier winding.

jwelser@ccwf.cc.utexas.edu wrote:
>
> I think what you're describing would still isolate the secondary
> from earth ground, which is exactly what an isolation transformer (or any
> transformer for that matter) does -- the secondary(s) are floating with
> respect to earth ground -- there is just "X" volts across the secondary
> coil.
>
> I've never heard of an auto-transformer before. Basically,
> it's a physical fact that any transformer that works by induction
> (basically any transformer, or so I thought) has it's secondary floating
> with respect to the primary -- put another way, because a transformer is
> an AC device, there can be any DC offset present between the primary and
> secondary and things still work. I'm not sure why any transformer would
> have its primary and secondary windings connected together, but, like I
> said, I've never heard of an auto-transformer before, so it's quite
> possible that's what's happening there.
>
> Joe
>
> On Wed, 3 Jul 2002, John Robertson
> wrote:
>
> > Not all transformers are isolation. There are the step up/down transformers
> > that one often sees in the Japanese and European video games to adjust the
> > input voltage from 115 to either 100 or 220 VAC. So, it is quite possible
> > to have a transformer in your junk drawer that is not isolation.
> >
> > John :-#)#
> >
> > At 09:00 AM 03/07/2002 -0400, James R. Twine wrote:
> >
> > > > From: Jon Raiford
> > > >
> > > > You didn't mention if these were isolation transformers and
> > > > there was no link to check.. Neil, make sure you use an
> > > > isolation transformer if you piece a replacement transformer
> > > > together!!
> > >
> > > This may sound naïve, but I was under the impression that the term
> > >"isolation transformer" simply meant a 1:1 transformer: a transformer
> > >whose input voltage was the same as its output voltage.
> > >
> > > IIRC, the purpose of an isolation transformer is to *physically*
> > >isolate the equipment from the power line, which all transformers do,
> > >anyway: they work by inductance. So by using *any* transformer, you
> > >would already get physical isolation...?
> > >
> > > Thoughts?
> > >
> > > Peace!
> > >
> > > > Jon
> > >
> > >[Get Check Favorites 1.4 Now! http://checkfavs.jrtwine.com]
> > >-=- James R. Twine, MCP, (jtwine@jrtwine.com)
> > >-----BEGIN GEEK CODE BLOCK-----
> > >Version: 3.12
> > >GCS d- s+:+ a29 C++++$ UL+++>++++ P+ t+++ 5+ X+++ tv+
> > >b++ DI++ G++ h e(++) r++ W++ N+++ w++(+++) M-- PS+
> > >------END GEEK CODE BLOCK------
> > >
> > >
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Received on Wed Jul 3 11:24:22 2002