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Modeling a magnifier



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From:  bmack [SMTP:bmack-at-frontiernet-dot-net]
Sent:  Monday, March 09, 1998 10:30 PM
To:  Tesla List
Subject:  Re: Modeling a magnifier

Antonio,

   I think we all agree that there will be a beat frequency with the
L2C2 and L3C3 connections you proposed. It still seems to me that the
C2 will be of an impractical size to tune L2c2  near (L2+L3)*c3.  I suspect
an actual system would have large radiation loses in the L2C2 and 
virtually no storage capability in C3.  The sparks would be very thin.
(Ok, I'm guessing here....)

The experiment is flawed if you are using a variable capacitor instead of
an isotropic capacity as in the real thing.  There is no actual ground 
connection as your model posseses.  That is what I was trying to say
in my last post referring to the " out of tune" impedance reflected into
the primary.  With your latest post , i see that you did not use a primary,
therefore you were unable to see this effect.  Check this out on your
grounded C2 experiment.  Replace it with an isotropic capacity of the same
value, and I'm sure there will be a marked difference in dynamics.
     In my opinion, a model closer to the actual system dynamics 
(simulation-wise)  might look more like this:
                         
      L2------+----------L3------C3----+
       |        C2                         Rr
       |        Rr                           |
       |         |                            |
       V       V                          V

     The "V" represents ground,  Rr is radiation resistance among other
things
such as ion channel absorbtion etc. There's been books written on the
nature
of Rr...buts thats another topic.  At low voltage- very much below
breakout,
it's pretty much a radiator.    This model will behave as Richard hull 
desribed his results, where C2 is more of a tuning issue for the L1C1
L2C2 coupled system than it is for the secondary.  The Q of the L2C2
section is impaired by Rr.   Depending on the degree that C2 is 
compensated for in the primary, there will be leway for some tuning
combinations and beats from these interactions.
      For C2<<C3 as in Richard's system,  It can be thought of like a
current
divider, where the most current will want to follow the (L2+L3)*C3 path.
 Again, the Thumbnail sketch to get in the ballpark is:

  L1C1=(L2+L3)*(C2+C3)

 As always, comments welcome.

Jim McVey

   







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        ----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: Modeling a magnifier
> Date: Monday, March 09, 1998 4:30 PM
> 
> 
> ----------
> From:  Antonio C. M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
> Sent:  Sunday, March 08, 1998 12:30 AM
> To:  Tesla List
> Subject:  Re: Modeling a magnifier
> 
> John H. Couture wrote:
> 
> >   Tesla also said that the secondary was acting in the transformation
mode.
> > This means it was not in resonance and the pri/sec voltage was the same
as
> > the turns ratio of the windings.   JC
> 
> Correct, but this happens only while the gap is conducting. After the
opening
> of the gap, the secondary is just a normal coil.
> 
> >   Could you explain the above in more detail. I'm confused about the
energy
> > oscillating after the gap is quenched.  JC
> 
> Consider the circuit formed by the secondary coil, the third coil, and
their
> self-capacitances. Ignore resistive losses:
> 
> +-----+--L3-+
> |     |     |
> C2    L2    C3
> |     |     |
> +-----+-----+
> 
> C2 includes the self-capacitance of the second coil L2, of the
interconnections,
> and the input capacitance of L3. C3 includes the self-capacitance of the
third coil
> L3 and the top capacitance.
> This circuit has two oscillatory modes, and if L2*C2=(L2+L3)*C3 it
oscillates
> exactly as a two-coil Tesla coil, with the same beating waveforms, that
periodically
> concentrate all the energy in C2 or in C3. (This can be demonstrated by
using the
> equivalence between a transformer to a T circuit of inductors.)
> Actually, you can build a Tesla coil variation exactly in this way.
> This is a model for the magnifier circuit after the spark gap is
quenched. While
> there is energy in the system, the double oscillation occurs.
> 
> Today I made some experiments at low power using the secondary of a Tesla
coil
> that I am building for L3-C3, another smaller coil for L2 and a variable
capacitor
> for C2. I charged the system by switching a high-impedance current source
across
> L2. I could observe clearly the beating waveforms and the energy
oscillation when
> C2 was set according to the equation above, exactly as in simulations
using this model. 
> I will prepare a full report about the experiment.
> 
> Antonio Carlos M. de Queiroz
> http://www.coe.ufrj.br/~acmq
> 
> 
>