Re: Parametric pumping for tesla coils?

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

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

On 15 May 2003, at 15:25, Tesla list wrote:

 > Original poster: "Jolyon Vater Cox by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >
 > Dear List,
 > If I may be so bold, I have been thinking that instead of using switching
 > devices to vary currents and voltages as we presently do, how about
 > changing say, the capacitance instead -charging at low voltage and
 > discharging at high
 > since charge ,Q,  on an isolated capacitor doesn't change with a change in
 > capacitance but stored energy and voltage do vary with changes in the
 > capacitance.

It does of course take at least as much energy to decrease the
capacitance as the energy increase in the final reduced capacitance.
Where will that energy come from and what sort of capacitor did you
have in mind?

 > Reading from previous postings on the List I understand that it is possible
 > to get more voltage out of the secondary of a transformer if the frequency
 > of the AC is increased -and vice versa-
 > the trouble is, the primary voltage must be increased or decreased in the
 > same proportion so there is normally no net advantage in changing the
 > frequency.

I don't understand that notion. The only change in voltage normally
appears as a result of resonance in the windings at high frequencies
due to parasitic winding capacitances.

 > However, if the capacitance of a capacitor, C, resonating in a tuned
 > circuit with an inductor ,L, at a frequency ,f1, is changed the oscillation
 > changes to a new frequency, f2, and with it the energy in the capacitor and
 > the voltage across it.
 >
 > Now, when a charged capacitor is connected to an inductor energy is
 > ordinarily lost in the "damped" oscillation -but if the capacitance (or
 > inductance) can  be made to change quickly enough it is possible to
 > overcome the losses resulting in a comtinuously-oscillating system. With
 > this in mind would it not be entirely possible -at least in theory- to use
 > these "parametric" methods in the pumping of Tesla coils?

Again, it takes energy to change the capacitance. The proposal
reminds me of Maxwell's demon in a way. It should be pointed out that
energy lost in the circuit is due to circuit resistances; also that
the capacitance cannot be decreased to zero so continuous oscillation
would appear to be an unreachable goal.

?
Malcolm

 > Could parametric TCs, Q-switching TCs etc, be just be round the corner?
 >
 >
 >