Re: Noncoupled Flux in Capacitive Transformers

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

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

with regard to ordinary loose-coupled tuned transformers  where the
secondary winding L2 forms tuned circuit with the capacitor C1, it is
possible for secondary circuit to be resonant
yet "seen" from the primary viewpoint  the circuit is still inductive due to
the leakage reactance of the primary.

to make the primary appear purely resistive at resonance  it is necessary to
decrease C1 to increase capacitive reactance referred to the primary across
the turns ratio in order to cancel the leakage reactance.

in a similar vein would it not be possible to use some of the inductive
reactance of L1 to cancel the leakage capacitance of c1 and C2 in the
instance of the capacitive transformer?

Also -on the slightly separate (?) issue of electric flux some of this does
"leak" through the capacitor C3 -if this were not so would there exist a
perfect capacitive transformer- a sort of dual of the theoretical "ideal
transformer" of magnetic design?

So -referring to the capacitive transformer Tesla coil-if the induction ring
could intercept all of the the electric flux between the ungrounded terminal
of L2 and ground, would that not be an ideal capacitive transformer -and no
more likely to exist in reality than an ideal magnetic one as some electric
flux would inevitably escape- not that any load could be connected between
the topload and ground of such a "transformer" in any case since the
influence plane would  have to totally enclose the ungrounded terminal
precluding such a connection.

Jolyon

gh
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, September 11, 2002 3:50 AM
Subject: Re: Noncoupled Flux in Capacitive Transformers


> 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>
> >
> > What is the effect of non-coupled electric flux in "capacitive
transformers"?
> > I know that the effect of non-coupled or "leakage" flux in magnetic
> > transformers is to effectively insert an inductance in series with the
> primary
> > of the theoretical "ideal" transformer and the resulting leakage
> inductance can
> > be made series-resonant with the secondary capacitance across the turns
ratio
> > -hence the big voltages in Tesla coils- but I amnot so sure about
non-coubled
> > flux in capacitive transformers:is there a comparable effect with
"leakage"
> > capacitance?
>
> The concept can't be applied exactly, because a "capacitive transformer"
> is not a true transformer, but just approximately behaves as one when
> the
> two capacitors are part of a resonant circuit. The circuit below
> resonates
> at the frequency w=1/sqrt(L3*C1*C2/(C1+C2)) rads/s.
>
>        +-----+-----o
>        |     |
>        C2    |
>        |     |
> o------+     L3
>        |     |
>        C1    |
>        |     |
> o------+-----+----o
>
> If you short-circuit the output of a step-up capacitive transformer
> you see the two capacitances in parallel, C1+C2, and this capacitance
> is effectively in series with the "transformer". It can be even moved
> to the output side, in series, using the "turns ratio" n=1+C1/C2,
> as (C1+C2)/(1+C1/C2)^2 = C2/n.
> This would be the "leakage capacitance", but it only appears with this
> value at the resonance frequency. Not very useful, I think. At least
> I didn't find a place for it in the design of the "capacitive
> transformer coil": http://www.coe.ufrj.br/~acmq/tesla/mres4ct.html
>
> Antonio Carlos M. de Queiroz
>
>
>
>