RE: Saturable Reactor

["Tesla list" <tesla@xxxxxxxxxx>]

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


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

Carl,

No heating is definitely goodness!  How many amps were
you pushing?

*****Between 60 and 70 Amps




Regarding the "quads", why do you need all the MOT
primaries in a quad to be in series?

*****Some series on the primary side appears to be necessary to allow
the system to handle 240 VAC.  All attempts to use various parallel
arrangements that worked on 120 VAC failed instantly on a high current
demand 240 VAC circuit.





For each pair, what is the "error" (unwanted AC) on the control side?

******It varied up to 400 VAC




  Just as with the individual MOTs in a pair, I would
think you could group pairs in a quad such that the
errors on the control sides cancelled out as much as
possible rather than adding up.
Of course, if the
errors differ wildly between pairs, you're out of
luck.

******We were out of luck on this possibility - too much variation


Trouble is, if you have to resort to putting
the primaries in series just to reduce the error on
each pair (by cutting the primary voltage in half, or
close to it), then you really aren't getting any value
out of the quads except for elimination of the
unwanted AC by voltage division.  You don't have any
more power handling capability than if two low-error
pairs were used in place of the quads, which is too
bad.

******Well, the 110 lbs of core iron certainly helps in keeping the
system cool. ;)  My principle PSU is a 3 stack Variac that puts out
0-480 VAC with 240 VAC in.  The quad MOT series keeps me from being
limited to 240 primary Volts and having 2 of these in parallel looks
like it will cover most current demand.  I would, however, like to be
able to get the high end current up to 100 Amps for some work.


I ordered eight identical MOTs which still haven't
arrived.  I can't wait!!  I'm really hoping they are
sufficiently identical to avoid the need for a lot of
careful pairing/quading.  We'll see, though.

******** Sounds interesting, good luck!

Regards,
Aaron, N7OE


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

 > 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
 >   >
 >   >
 >   >
 >
 >
 >