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Tesla Twin Configurations
---------- Forwarded message ----------
Date: Tue, 30 Sep 1997 19:53:29 -0400
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Tesla Twin Configurations
> ---------- Forwarded message ----------
> Date: Mon, 29 Sep 1997 19:17:23 -0700
> From: Skip Greiner <sgreiner-at-wwnet-dot-com>
> To: tesla list <tesla-at-pupman-dot-com>
> Subject: Tesla Twin
>
> Hi All
>
> Well I am finally back and hope to do some serious coiling again.
>
> I have a question.... I am going to put together a low power twin,
> probably about 2 kw input. I plan only to drive one secondary. The
other
> secondary will be direct coupled to the first primary....base to
base. I
> believe that the second primary should act as a perfect
counterpoise to
> the driven primary.
>
> The question.... Should the secondaries, when used in this
configuration
> be wound in the same direction or should they be wound in opposite
> directions?
>
> Thanks for any observations.
>
>
> Skip
Skip,
Since the second coil is strictly base driven, it does not matter in
what direction it is wound. In the first secondary the winding
direction has a definite phasing effect because it is
electromagnetically coupled. But your "extra" coil (for such it is)
is not electomagnetically coupled, but base current driven. As long
as the two coils are identical, they should fire arcs at one another.
Please note that unlike a magnifier, you have no earth ground
connection in this scenario, and *I* would be wary of burning up your
coils at the base, because they are not ground referenced. But they
will definitely seek ground, because there is still going to be a
tremendous "ground influence" caused by the proximity of good old
mother earth. If you connect the bases of both secondaries together
and then to ground, that will eliminate the HV at the base problem,
but the "extra" coil will then not oscillate as violently. That is
why for twin coils you are probably best off with electromagnetically
coupling them BOTH, each with its own primary.
Here are the different way you can connect something like a TWIN
coil:
[(1)Dual Primary / Dual Secondary, BOTH GROUNDED] This should be
phased so that the secondary ouputs are out of phase. This is
probably the most common twin configuration. Both coils are solidly
ground referenced. Good arcs, especially from secondary to secondary.
Arrangement is usually vertical and parallel. The most satisfying
results are obtained with this arrangement. This is the type of Twin
Coil that Ed Wingate has. Maybe he will share his wisdom in this area
with us. Excellent results can be had with this design.
[(2)Single Primary / so-called 1/2 Wave Secondary, NO GROUND] This
configuration is really a Dual 1/4 wave setup. BOTH halves of the
secondary are electromagnetically coupled to the single primary.
Proper phasing is achieved automatically (the two ends are out of
phase). It is generally a horizontal arrangement. Because there is no
ground connection on either half of the secondary, this type coil is
best used for throwing arcs from end-to-end. If you approach one end,
it will imbalance the coil and the center of the secondary will
attempt to arc to the primary. It is a horizontal arrangement
generally, and is therefore harder to implement in the larger sizes.
To get the large arcs from end to end, you have to provide rods that
go out and bypass the primary. A reasonable performer, but has too
many problems because of its horizontal nature. This type coil is
generally disappointing, as streamers are not as brilliant as in
version (1). A version of it is often found in physics labs.
[(3)Single Primary / so-called 1/2 Wave Secondary, CENTER of
Secondary GROUNDED] This configuration is really a Dual 1/4 wave
setup. BOTH halves of the secondary are electromagnetically coupled
to the single primary. Proper phasing is achieved automatically (the
two ends are out of phase). It is generally a horizontal arrangement.
This arrangement is better than the previous arrangement, because of
the center ground. This eliminates most of the tendency to arc to the
primary. It is a horizontal arrangement generally, and is therefore
harder to implement in the larger sizes. To get the large arcs from
end to end, you have to provide rods that go out and bypass the
primary. A reasonable performer, but has too many problems because of
its horizontal nature. (It is almost the same as (1) except it is
horizontal and shares a single primary)
[(3.5)Single Primary / so-called 1/2 Wave Secondary, CENTER of
Secondary GROUNDED, center of Primary GROUNDED] This configuration is
really a simple variation on (3), the Dual 1/4 wave setup. BOTH
halves of the secondary are electromagnetically coupled to the single
primary. Proper phasing is achieved automatically (the two ends are
out of phase). It is generally a horizontal arrangement. This
arrangement is better than the previous arrangement, because of the
center ground. The added feature here is that the center of the
secondary is ALSO grounded. This TOTALLY eliminates the tendency to
arc to the primary (at least at the center). If you want to be picky
about it, it is now a Oudin Coil. (Oudin coils have the secondary
connected to the primary. Other than that, they are true Tesla coils
and operate on identical principles). It is a horizontal arrangement
generally, and is therefore harder to implement in the larger sizes.
To get the large arcs from end to end, you have to provide rods that
go out and bypass the primary. A reasonable performer, but has too
many problems because of its horizontal nature. (It is almost the
same as (1) except it is horizontal and shares a single primary)
[(4)Single Primary / Secondary UNGROUNDED, EXTRA COIL] In this
arrangement one secondary is electromagnetically coupled to the
primary, and the other is not. The two secondaries are directly
connected to one another. The EXTRA coil is base driven by the base
current of the first secondary. The problem here is that the base
currents developed rely totally on the counterpoise action of the two
coils. Because there is no ground reference, the tendency to arc from
the base of the secondary to the primary will be tremendous. This is
the arrangement that Skip is contemplating. Probably contemplating a
vertical orientation of the secondaries. I don't think it is capable
of the kind of base currents that you can get with a grounded system.
It is finicky, and when you approach either of the coils it causes an
imbalance in the circuit. Somewhat hazardous because it is
ungrounded, but will be seeking ground when any external object
approaches.
[(5)Single Primary / Secondary Grounded, EXTRA COIL, also GROUNDED]
This is actually a form of Free Resonator. Richard Hull shows Alex
investigating this arrangement in one of his tapes. Investigations of
this eventually led to full-blown magnifier experiments. Malcolm
Watts recently discussed a special coil he built and experimented
with. He ran it both in mode (4) and mode (5). I believe he found
mode (4) gave greater arcs between secondaries, but was more finicky
in operation. (Probably due to ground influences). Malcolm found that
arc length was smaller with mode (5). I believe this is because
ground was absorbing some of the base current, so less was available
to drive the extra coil.Malcolm Watt's Twin Coil was a multiple layer
coil with a core, more akin to some of the early iron core high
frequency coils invented by Tesla before he invented the air core
Tesla coil. Maybe Malcolm can enlighten us as to the details of his
experiments as they pertain to this discussion of twin coils.
I hope I have covered most of the bases here. Someone like Ed Wingate
is more qualified in this area. I have built all of these
configurations, but only on a small table-top scale. Ed has built
some truly massive bolt hurlers!!
Ed? Malcolm? Anyone else care to add something to this discussion?
Hope this helps.
Fr. Tom McGahee