RE: Saturable Reactor

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Out standing!

I am going to simulate the results with a three phase transformer 220V
(Taps) 5000V out supposedly @ 1 amp. The transformer is 75 lbs. 175lb for
(6)833a's just disappeared off eBay, pronto.

I would like to be able to ground (should be isolated) the core if all hell
breaks loose, seemingly a distinct safety advantage. I'm not sure that this
tyranny is up to much more than 5 KW unless both outers LV's can carry the
220 5 KW ea and the center HV leg can Sat the transformer. I don't want to
smoke this baby as I plan to use it for an 883a coil down the road apiece...

What is the consensus on the unused pairs? I like Aaorn's idea of using the
center leg HV for the DC control but I guess all is moot until I can get
some measurements off the transformer. And note the wire gauges, DC
resistance, and L of the windings.

Then I'll be back for some suggestions!

Jim Mora
Ojai,ca.


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Monday, March 06, 2006 3:25 PM
To: tesla@xxxxxxxxxx
Subject: RE: Saturable Reactor

Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx>

We would love to see someone produce an SR using a couple of small pole
pig (or mini-pig) transformers as suggested below!

We were also able to complete our series of tests on the MOT type
reactor this past weekend.

The previously reported series pair reactor was scaled up to 4 pairs of
MOT's each wired in this manner.  We did not have 8 absolutely identical
MOT's so we knew there would be some voltage developed in the control
winding with such a large and varied configuration.  Several connection
schemes were tried in the attempt to produce the most suitable
inductance range while limiting the voltage in the control to the
minimum.  The optimum arrangement with the particular transformers we
used turned out to be to construct two quads in which all 4 units of
each were placed in series aiding with each other on the primary side
and then to connect the two quads to the test circuit in parallel.  As
before, all of the secondaries forming the control were wired in series
opposing between pairs of MOT's and the pairs then wired together in one
continuous series.  The result was about 50 Volts in the control when
the reactor was placed in a 240 VAC circuit.  Approximate schematic
here:

http://hvgroup.dawntreader.net/8motschematic240v2

As a sort of 'acid test,' we chose to ballast a 10 kVA pole pig with the
reactor.

http://hvgroup.dawntreader.net/reactoronpig.jpg

http://hvgroup.dawntreader.net/reactorandcontrol.jpg


With no DC in the control, there was produced only a tiny hissing spark
between the uprights of Jacob's Ladder attached to the pig, indicating a
high reactance and very low current.

http://hvgroup.dawntreader.net/nocontrolvoltage.jpg

Introduction of 20 to 30 VDC into the control resulted in the widening
and lengthening of the arc that then began to travel part way up the
ladder.

http://hvgroup.dawntreader.net/lowcontrolvoltage.jpg

Increasing the voltage in the control winding to its full value of about
140 VDC caused the ladder to spring to life in its familiar form - a hot
billowy plasma arc that traveled the full length of the ladder.
Increasing the control voltage to 525 VDC produced no noticeable change

http://hvgroup.dawntreader.net/fullcontrolvoltage.jpg    (little blurry
but recognizable)


After allowing the ladder to run for several minutes with the reactor
wide open in its maximally saturated state and therefore with maximum
current in the test circuit, all power was cut to the circuit and the
reactor inspected for problems.  Amazingly, there was no detectable heat
in any of the transformers.  This is considered a very successful test
of this configuration..

Our thanks to Aaron and all others on both lists who contributed helpful
suggestions and comments to this and related threads regarding this
interesting concept.


Carl Litton
Memphis High Voltage Group



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Sunday, March 05, 2006 7:32 PM
To: tesla@xxxxxxxxxx
Subject: Re: Saturable Reactor

Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>

MOTs seemed ideal because they're cheap, relatively
HV, and available.  The problem with common 240/480
three-phase transformers is that the windings are
going to have very low DC resistance, owing to
heavy-gauge windings and relatively few turns in those
windings.  These characteristics will mean that your
DC control will have to put out quite a bit of current
at a very low voltage, which is a little awkward.

I tried to locate a three-phase transformer having a
high voltage of 2400-4160V, which would tend to imply
a higher DC resistance on the HV winding, and
therefore a better chance of using one or more of the
HV windings for a control winding by simply hooking up
a recitified variac.  I did immediately locate a 3kVA
4160V-240V transformer on eBay, but the guy wanted
almost $500 for it!  By contrast, my local utility
offered me a 75kVA three-phase unit, 14.7kV-480/277V,
for $300 (they're nice to me :))  It was oil-filled
and weighed several tons.  Had to turn that one down,
though! (maybe someday I'll have the real estate to
play with something like that).

...but there's nothing magical about the MOT idea.
Pairs of identical pole transformers ought to work
nicely, too.  When talking about stuff like that,
however, I start to get pretty worried about what
might happen if one pig should fail.  In fact, even
with MOTs, I'd like to see some more research done
into how to make the MOT-based SR's safe.  Not pushing
them too hard certainly seems like a good idea!!

Regards,
Aaron, N7OE

--- Tesla list <tesla@xxxxxxxxxx> wrote:

  > Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
  >
  > Most recent talk about SR's has been on MOT's, but I
  > seem to remember someone mentioning a 3 ph. dry type
  > distribution transformer, such as this one:
  >
  >
http://www.hot-streamer.com/adam/garage/transformer_30a_kVA.jpg
  >
  >
http://www.hot-streamer.com/adam/garage/transformer_30b_kVA.jpg
  >
  > Has any further work been done for something like
  > this?
  >
  > thanks
  > Adam
  >
  >
  >