Re: Proposed capacitive transformer TC?

["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>
> 
> Another point -if the  "indirectly-coupled" circuit is rearranged so that
> in series with L2 base and ground, and the capacitive coupling between L2
> and metal plane is replaced with a wire connection to discrete capacitor
> with value of 1nF (as in  the "direct-coupled" circuit)  aren't the two
> systems in fact the same?

Let's see if I understand the idea:

The directly coupled system is:

                        (=====) Terminal
                           |
                           L2
                           |
    o------+--C1--+--------+
           o      |        
   PSU    gap     L1       
           o      |        
    o------+------+---------o Ground

The lumped model for it is:
                       
    o------+--C1--+---L2---+
           o      |        |   
   PSU    gap     L1       C2
           o      |        |
    o------+------+--------+

The capacitively coupled system is:

                        (=====) Terminal
                           |
                           L2
                           |
    o------+--C1--+----(=) | (=) Influence plane
           o      |        |
   PSU    gap     L1       |
           o      |        |
    o------+------+--------+-o Ground

Its lumped model is:

    o------+--C1--+---C2---+----+
           o      |        |    |
   PSU    gap     L1       L2   C3
           o      |        |    |
    o------+------+--------+----+

If C3=0, or, if the influence plane captures all the electric field of 
the secondary system, the two systems are equivalent.

But the presence of C3 causes a change, that essentially forces 
operation at a slower mode.

I found that a model that describes very precisely the system that I 
built, ignoring losses, is:
C3 =  6.05 pF
C2 =  5.18 pF
L2 =  28.2 mH
C1 =  1 nF
L1 =  315 µH
It works in mode 20-21, as measured, with a voltage gain of 9.46.
It oscillates at 276 and 290 kHz and shows perfect energy 
transfer in 10.5 cycles. C3 is 54% of the load capacitance.

The original directly coupled system works in mode 9-10, that is 
about twice faster, less lossy, and less sensitive to tuning.
It oscillates at 270 and 300 kHz and transfers energy in 5 cycles.
The voltage gain is 9.53.

This kind of coil is interesting to explain how the "energy 
transmission" at distance works, considering only the electric
field influence at distance (that is more important than the
magnetic field influence). With local fields only and irradiation
ignored, the system is essentially lumped, with C2 being the
capacitance between the transmitter and receiving antennas, and
C3 being (~) the remaining part of the receiver capacitance to 
ground. Ideally, in the absence of losses, complete energy transfer
is always possible, even with voltage gain. But the reducing of
C2 in relation to C3 causes an increase in the number of cycles 
required for complete energy transfer, increasing the losses
and turning the tuning more critical.

Antonio Carlos M. de Queiroz