[Prev][Next][Index][Thread]
Voltage/Length (fwd)
----------
From: Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent: Tuesday, February 10, 1998 8:28 PM
To: Tesla List
Subject: Re: Voltage/Length (fwd)
Tesla List wrote:
>
> ----------
> From: HomerLea-at-aol-dot-com [SMTP:HomerLea-at-aol-dot-com]
> Sent: Monday, February 09, 1998 10:12 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Voltage/Length (fwd)
>
> In a message dated 98-02-09 05:51:45 EST, you write:
>
> > > The equation Vs = Vp sqrt(Cp/Cs) follows directly from
> > > Conservation of Energy, and simply sets an _upper limit_
> > > for Vs. It's true that Vs can drop below this amount
> > > if the coil is inefficient, but Vs can never be _larger_
> > > than this quantity.
> >
> > Unquestionably true!
> >
> Not so!!!!!!!!!!!!!!!!!!!!!!!! It seems that the whole idea of a Tesla
> coil(resonance) is being overlooked in this discussion. The above equation is
> valid if, one time, you take all the energy from one capacitor and transfer
> it to another cap . In a resonant system you are taking oscillations or pulses
> from one system (Tesla primary) and adding them up in a second system (Tesla
> secondary -- an LC energy storage reservoir).
>
> The equation Vs = Vp sqrt(Cp/Cs) should be Vs = Vp sqrt(NCp/Cs) where N is
> the number of cycles or pulses transferred from the primary (if at 100%
> efficiency).
>
> A bigger torroid gives a bigger spark because it allows the voltage to rise
> to a higher value before "breakout"(allowing N to be larger). If 100%
> efficiency could be reached, a giant torroid would allow the primary to pump
> up the secondary LC system for a week with one spectacular spark at "breakout"
> from the torroid (and a very large voltage).
>
> jim heagy, rambling on
Jim,
Close, but no cigar, Jim! When k is significantly smaller than 1, it
takes a number of half-cycles to transfer all the energy in the primary
to the secondary. The lower the coefficient of coupling, the larger the
number of half-cycles required for this transfer to complete. For
example, if k = 0.6, the transfer will complete in two half cycles, and
if k = 0.22, it takes 5 half cycles to complete. If there were no other
losses, the amount of energy transferred to the secondary, after the
appropriate number of half-cycles, is still limited to the energy/bang
originally stored in the primary tank cap at the instant the gap fired.
Conservation of energy and all that...
Now let's suppose we have a perfect quench at this time and open the
gap. The secondary will now "ring down" from its maximum energy level at
a rate governed by its Q. Now its "effective" Q is a very strong
function of how good an RF ground you've got, and whether you're losing
energy to streamers. Heavy streamer loading can reduce a secondary's Q
from say 150 or so to less than 10. However, even if we don't have any
streamers, in virtually ALL disruptively energized coils there's
virtually NO energy left in the secondary by the time the primary gap is
ready to fire again. What this means is that there's NO carryover of
energy from ONE bang to the NEXT one, hence no chance of "adding" energy
to the secondary from one bang to the next. Each can be treated as a
separate event. This also means that the BEST you can hope for is only a
large fraction of Vs = Vp sqrt(Cp/Cs) in a disruptively excited coil -
80 - 85% is doing great!!
Now a CW-driven coil CAN show energy increases on a cycle-cycle basis
until the rate of energy loss from corona and other losses = rate of RF
energy input from the power oscillator.
Hopes this clarifies the situation a bit... and safe coilin' to you!
-- Bert --