Re: Transformerless Tesla coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:

> Original poster: "Jolyon Vater Cox by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

> Re: the subject of the transformerless tesla coil, would it not be possible
> to design a twin transformerless TC by combining a directly-coupled Tesla
> Coil with an indirectly-coupled TC like so:-
> 
>                     (===)        (===)
>                       I            I
>                       L2           L3
>                       I            I
> -----C1-----+----+----+            +
> I           I    I                 I
> SG1         L1   I                 ------GND
> I           I    I
> ------------+    I   --+--       --+--
>             I    I     I           I
>            GND   I    GND          I LIVE
>                  I                 I
>                  -------------------
> Both TC's (L2 and L3) are transformerless Magnifiers capacitively coupled to
> oppositely-charged planes.
> L2 is connected to the "live" side of L1 and its plane is grounded.
> L3 is connected to grounded side of L1 and its plane is "live".
> I.e. L2 is charged by conduction and L3 by
> electrostatic induction.
> 
> Does the illustration above not give insight into the equivalence of of the
> two circuits;
> in both electrostatic coupling takes place between topload and the planar
> electrode,
> whether the extra be live and the plane grounded OR VICE-VERSA.

A nice idea.
The idea would work, but with a small modification. The capacitively
coupled section is slower due to the presence of the capacitance between
the terminal and the ground, and so the directly coupled section must
be slowed down too for a perfect match. This can be done by adding an
induction plane around the resonator of the directly coupled section
too, also connected to the top of L1 (and not to the ground as in your
drawing):

                        (=====)a    (=====)b
                           |           |
                           L2          L2'
                           |           |
    o------+--C1--+----(=) | (=)---(=)-+-(=) <-Two influence planes  
           o      |        |  
   PSU    gap     L1       |
           o      |        |
    o------+------+--------+---------------o Ground

A lumped model of the configuration is:
                                    
    o------+--C1--+------+---------+----+
           |      |      |         |    |
           |      |      C2        L2'  C2' 
           o      |      |         |    | 
   PSU    gap     L1     +----+a   +----+b
           o      |      |    |    |         
           |      |      L2   C3   C3'  
           |      |      |    |    |      
    o------+------+------+----+----+

C2 and C2' are the capacitances between the influence planes
and the resonator coils. C3 and C3' are the capacitances to
ground of the resonators.
The circuit is a bridge, where an output voltage with doubled
amplitude can be taken between the two terminals (points a and b).
For perfect balance, the circuit shall be adjusted so 
C2'=C3 and C3'=C2. 
In the circuit that I built, C2 is aproximately equal to C3,
and so to make this circuit it would be enough to add another
identical resonator and influence plane, and divide by two
the impedance level of the primary circuit, Using 2*C1 and L1/2
instead of the original L1 and C1.
There is the complication of the capacitance between a and b,
not considered. It can just be multiplied by 2 and added to 
C3 and C3' if the circuit is balanced.
Looks tricky to tune, but possible.
 
> Also, isn't the unwanted capacitance C3 that slows energy transfer in the
> indirectly-coupled coil also to be found in the directly coupled version as
> the capacitance between leads of the extra coil- and in both devices is not
> the maximum voltage to be found between the topload and the opposing plane?

This would be C2' in the schematics above. In a normal circuit it 
certainy exists, but is much smaller than C3', formed by the combination
of the self-capacitance of L2' and the terminal capacitance. C2' is only
significant if the influence plane is installed, "capturing" part of
C3'.

I added a comment about the "capacitive transformer" in the page about
the capacitive transformer Tesla coil:
http://www.coe.ufrj.br/~acmq/tesla/mres4ct.html
The "transformer" is not only formed by C1 and C2, but also by L1.
I also tested a version with 5 times higher power, and now the
antenna produces small streamers, and not only corona (not there yet).

Antonio Carlos M. de Queiroz