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Re: Bang size and break-rate
In a message dated 99-06-12 12:42:25 EDT, you write:
<< Asuming the coils are run with a 100 BPS rotary (50Hz), and the cap is
> sized to be resonant, then the cap will be quite small, therefore the
> pri. coil must be big, and the power throughput small also.
> So a big primary not only ensures secondary magnetic engulfment, it also
> ensures low power input at 100 BPS. (50 Hz)
Hi Finn, all,
I have some doubts that a large dia primary will engulf any more
of the secondary than a small dia one. I would think that in either
case, the great majority of the coupling would occur near the base
of the secondary, and I would think that as long as the coupling is
OK, and the primary doesn't arc between turns, it's OK whether it's
big or small.
> Terrys recent post about calculating power in, filled in the missing
> piece:
> Take my 20 kV, 3 kW pig for an example: Resocap:0.0199 nF
> At 100 bps it will take 0.5 * 28200^2 * 20e-9 * 100 = 795 watts to
> charge the cap.
>I am using a 34 nF cap, which charges with: 1351 Watts, so It would seem
> probable that with a static gap my coil is running 200 - 300 BPS with
> the power available. (Based on the sound, it is running 300 BPS, it
> changes pitch 2 times, when I turn the variac up) But with a rotary, all
> I would gain with this power would perhaps be a ring of fire in the
> rotary.
Yes, with a small cap, lowering the break rate will reduce the the output.
If you're going to lower the break rate, you need a larger cap or higher
input voltage, to create a larger bang size. I don't think the resonant
calcs apply to non shunted transformers, since you can ballast them
as needed. Also, I agree that a larger cap is better for your system.
> The sizing of the cap for most beginners is made by the various tesla
> programs, but it seems like I would be doing better with a 80 nF cap, to
> match available power to 100 BPS.
> Now this would bring the primary down from 15 turns to 7.5, still not
> too few, however, if I was to change the transformer to say 10 kW, the
> cap would have to be 200 nF and this would translate to 4,5 turns
> primary. I would assume There would be a problem, then.
There are some who say that 4 or 5 turns are the perfect number. In
any case, if the coil is physically large, the inductance will increase
even though the number of turns is small. Greg Leyh's super coil has
only 4 turns I think, and it gives great performance. His cap is 0.225uF
with 26kV peak on the tank. He uses 350 bps for a 25 foot spark. His
new Electrum coil uses 0.27uF, at 43kV, at 110 bps (?) and gives
30 to 40 foot sparks, and up to 50 feet i think at a higher break rate.
I'm just writing this from memory so there may be some error.
One way to get more turns (or more inductance) in the primary, is to
use more turns in the secondary of thinner wire. This is the method
I use.
> But would it be a problem due to power throughput, more than a problem
> of magnetic coupling?
> So maby RQ was just trying to preserve the coils from abuse?
>What to do:
> I _must_ get the scope to record breakrate.
> I _must_ get confirmation that the reso-cap estimate should be taken off
> the tesla programs, and replaced with calculations based on actual power
> throughput ability of the cap.
> Find out if it is possible to predict the coupling of the coils, without
> actually building them.
Some of the programs can predict the coupling.
>And be happy I am part of this forum :-)
Yes, it's great, thanks to Chip, Terry, and all the list members, and
modern technology.
Cheers,
John Freau
> BTW: coil described is on display at:
> http://home5.inet.tele.dk/f-hammer/tesla/tesla.htm
> Cheers, Finn >>