Re: Saturable Reactor Ballast - further testing 1 and SAFETY note

["Tesla list" <tesla@xxxxxxxxxx>]

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
>  > appears that if
>  > identical transformers are used, the primaries
> must
>  > be wired in
>  > 'cross/inverse/anti' (pick a term) parallel -
> that
>  > is the LEFT input tab
>  > of one MOT is connected to the RIGHT input tab of
>  > the other MOT in the
>  > pair and visa versa in order to have low or no
>  > voltage in the control.
>  > Of course, this is predicated on the use of the
> HV
>  > tabs to connect the
>  > secondaries in series, which as you can see is
> what
>  > we are using.
>  > *******
>  >
>  > There also appears to be no reason that the
>  > primaries of each pair may
>  > not be connected in series (making sure that they
>  > are wired such that no
>  > voltage is induced in the secondaries) and then
> the
>  > pairs connected to
>  > each other in parallel.  This configuration may
> be
>  > more suitable for
>  > heavy current work in the 200-300 VAC range.
>  >
>  > The suggestion of putting parallel MOT's in each
>  > half of the phase in a
>  > 240 VAC circuit may possibly be less
> satisfactory.
>  > The two legs of the
>  > split phase are only 120 VAC *with respect to
>  > ground.*  They are 240 VAC
>  > with respect to each other.  The MOT's are
> floating
>  > in this type of SR
>  > and will be subjected to 240 VAC if placed in the
>  > circuit in this
>  > manner.  Another consideration is that they will
>  > then be 2 inductors in
>  > series and as such, their inductances will be
>  > additive in the circuit.
>  >
>  > More results soon . . .
>  >
>  >
>  > Carl Litton
>  >
>  >
>  >
>  >
>  > -----Original Message-----
>  > From: Tesla list [mailto:tesla@xxxxxxxxxx]
>  > Sent: Friday, February 24, 2006 10:05 PM
>  > To: tesla@xxxxxxxxxx
>  > Subject: Re: Saturable Reactor Ballast for TC
> from
>  > MOT's
>  >
>  > Original poster: tesla <tesla@xxxxxxxxxxxxxxx>
>  >
>  > Hi Carl et-al
>  >
>  > I agree with Finn this appears to be an invention
> of
>  > importance to
>  > coilers
>  >
>  > Another configuration that might work is to
>  > configure as an inductive
>  > voltage divider. ie a pair, one with L set high
>  > while the mate is low
>  > (like
>  > a potentiometer) This would create a true
> variable
>  > voltage divider
>  > operating
>  > in the range 0.93 down to 0.06.
>  >
>  > Not a variac but could be a useful device
>  >
>  > Rgds
>  > Ted L in NZ
>  >
>  >
>  >
>
>
>