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

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!)


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

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.

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