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Re: 50%
Tesla List wrote:
>
> >From ed-at-alumni.caltech.eduWed Oct 30 22:01:26 1996
> Date: Wed, 30 Oct 1996 17:17:22 -0800 (PST)
> From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com, tesla-at-pupman-dot-com
> Subject: Re: 50%
>
> I agree with Bert's model. There is no problem at all
> in getting very close to 100% energy transfer in a reactively
> coupled circuit with low losses; that's how almost all RF coupling
> circuits work. The "two capacitors shorted together" model gets
> into trouble because, if there is zero resistance, an infinite
> current flows through zero resistance for zero time! Add an
> arbitrarily small amount of resistance in the circuit and conventional
> circuit theory works fine and all of the "missing energy" turns
> up as heating of the resistance.
In the zero resistance model or the 1 megohm model all the energy was
lost to resitive or heat losses. The energy never made it to the other
cap!! Energy is always conserved, yes, but just doesn't wind up where we
want to have it! As in the Tesla coil. (sparks from charged up air based
on resonant rise) R. Hull
> Consider a very simple model, such as is found in "boost"
> type switching voltage converters. Connect a low-loss inductor
> in series with a battery. The "free" side of the inductor is
> connected to a capacitor through a diode such that the inductor
> is connected to the positive terminal of the battery, the capacitor
> ground end to the negative, the anode of the diode to the "free"
> end of the inductor, and the cathode to the floating end of the
> capacitor. Switch the free end of the inductor to ground and let
> current build up (i=E/L*t). After some period of time open the
> switch which ground the inductor. The voltage across the inductor
> will rise (instantaneously) to a voltage which causes the same
> current to flow into the capacitor through the diode. As time
> goes on the current will flow until the capacitor until all of the
> energy stored in the inductor (1/2 * LI^2) is now stored in the
> capacitor (1/2 * CV^2), the current AND THE RATE OF CHANGE OF
> CURRENT have dropped to zero. All of the energy stored in the
> inductor has now been transferred to the capacitor, and the circuit
> is in steady state. To the extend that there was finite resistance
> in the circuit there will have been a small energy loss, but that
> can, in principle, be made arbitrarily small without invoking any
> extraordinary laws of physics. This example is analogous to the
> tesla coil when the current in the primary is interrupted at the
> correct time. In my 1915 "Wireless" text by Zelenick there are
> photos of primary and secondary voltage waveforms, taken with the
> very crude apparatus of the day (in some cases just neon bulbs
> observed with a rotating mirror to provide a time sweep) which
> clearly show the phasing of the "beats" in the primary and
> secondary circuits.
> For what it's worth,
> Ed Phillips
>
> Ed,
I use and spec switching supplies all the time, and am aware of their
extreme efficiency. But, we have only a SINGLE super nice cored choke
where the fulx is nicely trapped and held in a hi mu material just
itchin' to give it all back to the windings and a SINGLE capacitor in
this scenario! We have not taken the energy stored into the single
capacitor and then charged another pure capacitance with it. If we did
we would expect the demanded 50% energy loss and conservation of charge.
The Tesla coil, as we use 'em, are always 100% air core items and loosely
coupled to boot. Lotsa' losses just in this area. The spark is the only
output of the coil we are concerned with and it is a function of terminal
volatge and terminal capacitance. q=cv Charge must be conserved in this
system too.
Richard Hull, TCBOR