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Re: Saturable Reactor Ballast - further testing 1 and SAFETY note
Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
Actually, forget that (the "fake neutral" idea). On
second thought, it *wouldn't* work :(( Thinking about
what would happen when the pig output was shorted, it
would basically short one of the MOTs, putting all
240V across the remaining MOT. Bad, bad, bad...oh
well. Get a couple of 120V variacs. The whole
problem disappears then :))
Regards,
Aaron, N7OE
--- Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "J. Aaron Holmes"
> <jaholmes@xxxxxxxxxxxxxxxxxx>
>
> If you're stuck without the ability to use the
> neutral
> because you're using a 240V variac instead of ganged
> 120V variacs to drive your pig, then perhaps the
> thing
> to do is wire all of the series connections between
> MOTs (which would otherwise be floating) to the pig
> neutral. These would be like a "fake" neutral
> connection to the pig. Let the pig LV side act like
> a
> big voltage divider to stabilize the MOT primaries.
> There would be no neutral connection from the supply
> in this case. Here's a simple two-MOT example of
> what
> I'm talking about, and it can easily scale to any
> number of pairs:
>
> http://silicon-arcana.com/MMSR2.gif
>
> Would *that* work? I think it would... IMO,
> letting
> the series MOT connections float isn't just badness,
> it's not necessary. At least not *completely* :-)
>
> Regards,
> Aaron, N7OE
>
> --- Tesla list <tesla@xxxxxxxxxx> wrote:
>
> > Original poster: Yurtle Turtle
> <yurtle_t@xxxxxxxxx>
> >
> > One possible problem to using the pig neutral is
> > that
> > lots of folks use single (or parallel) 0-240 volt
> > variacs, which places both LV sides at -120 volts
> at
> > zero power. One side stays at -120, while the
> other
> > side goes from -120 to zero, then to +120 as the
> > variac is ramped up. (I know it's not really "-"
> and
> > "+", but that's the easiest way to describe it).
> Of
> > course if you use two ganged 120 volt variacs
> this
> > isn't a problem.
> >
> > Adam
> >
> > --- Tesla list <tesla@xxxxxxxxxx> wrote:
> >
> > > Original poster: "J. Aaron Holmes"
> > > <jaholmes@xxxxxxxxxxxxxxxxxx>
> > >
> > > Carl, can you comment on the heating of the
> MOTs
> > > under
> > > load? What kind of throughput is reasonable
> to
> > > expect
> > > without a lot of fancy cooling? I (and I
> suspect
> > > many
> > > others) would love to see a big Jacob's ladder
> > > running
> > > with this thing as a ballast!!! :)
> > >
> > > Regarding the 240V approach, see the
> "Eight-MOT
> > > reactor for 240V" at the bottom of the
> following
> > > image
> > > (may need to zoom it; it's big!)
> > >
> > > http://www.silicon-arcana.com/MMSR.gif
> > >
> > > If you notice, I called out the Neutral
> > connection
> > > even though it plays no role in the reactor
> > itself.
> > > Still, if you connect Neutral to the center
> lug
> > of
> > > your pig's LV, ballasting the pig can be
> thought
> > of
> > > as
> > > ballasting two separate transformers, one on
> Hot
> > 1,
> > > another on Hot 2. The MOT config on each of
> > these
> > > is
> > > ***absolutely identical*** to the four-MOT
> > ballast
> > > you're talking about. The only difference is
> > that
> > > the
> > > control windings of each four-MOT pieces are
> in
> > > series. So you see, there is actually
> *nothing*
> > > floating on the power side of things, which
> IMO,
> > > makes
> > > it vastly preferrable to putting MOT primaries
> in
> > > series.
> > >
> > > But, there may be 240V transformers in use in
> the
> > TC
> > > community that do not have a Neutral
> connection,
> > in
> > > which case you're probably stuck with the
> series
> > > primary arrangement.
> > >
> > > Regards,
> > > Aaron, N7OE
> > >
> > >
> > > --- Tesla list <tesla@xxxxxxxxxx> wrote:
> > >
> > > > Original poster: "Carl Litton"
> > > > <Carl_Litton@xxxxxxxxxx>
> > > >
> > > > Thank you, Ted.
> > > >
> > > > This thread seems to have generated some
> > > interest.
> > > > So, we though some
> > > > here might appreciate an update on the 8
> MOT
> > > reactor
> > > > we configured this
> > > > past weekend.
> > > >
> > > >
> > http://hvgroup.dawntreader.net/8motreactor2.jpg
> > > >
> > > >
> > http://hvgroup.dawntreader.net/8motreactor1.jpg
> > > >
> > > >
> > > > This concept appears to be amazingly
> versatile
> > > with
> > > > a large number of
> > > > possible configurations to address the
> > particular
> > > V
> > > > and I parameters of
> > > > its intended application. We have verified
> > the
> > > > hypothesis posted Friday
> > > > that the control windings may be placed in
> > series
> > > > rather than parallel
> > > > to give a higher and wider control voltage
> > range
> > > > without ill affect. In
> > > > fact, with the 8 pack above, we placed the
> > > control
> > > > windings of all 4
> > > > pairs of MOT's in one continuous series,
> > > resulting
> > > > in a control range of
> > > > about 0-100 VDC.
> > > >
> > > > Placing the additional 2 pairs in parallel
> > with
> > > the
> > > > first 2 pairs did,
> > > > as expected, drop the high end reactance to
> 15
> > > Ohms.
> > > > The low end
> > > > remained 2 Ohms.
> > > >
> > > > READ THIS ****** We also tested the idea
> > > suggested
> > > > here on this list
> > > > that the primaries should be placed in
> > 'straight'
> > > > parallel - that is the
> > > > left input tab of one MOT connected to the
> > left
> > > tab
> > > > of its pair partner
> > > > and the right to the right of the other.
> > PLEASE
> > > > NOTE that this results
> > > > in nearly 4000 Volts in the control
> winding.
> > It
>
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