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STUPID SIMULATIONS
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Monday, September 22, 1997 4:11 PM
To: tesla-at-pupman-dot-com
Subject: Re: STUPID SIMULATIONS
Thanks Mark,
Just interested to see what would come out of it. The 3'
from the 12kV 90mA setup was with a dual static gap and the resonator
was 22" x 4.5" wound with 23AWG (yes - I have the wire conversion
charts :). The one I compared it with was 20" x 6.6" spacewound
with the same wire. V stepup was much the same. Top terminal was a 9"
sphere in both cases (about 7pF on those coils). BTW, I have obtained
3' with 12kV -at- 60mA but not nice smooth firing sparks - big erratic
bangs.
> From: Mark S. Rzeszotarski, Ph.D.[SMTP:msr7-at-po.cwru.edu]
> Sent: Monday, September 22, 1997 2:46 AM
> To: Tesla List
> Subject: Re: STUPID SIMULATIONS
>
> Hello Malcolm and all,
> Malcolm said in part:
> <snip>
> >I would be interested if you did a run on a 6.6" coil, Hs about 21"
> >with a topload of 7pF. On what basis are you choosing the wire size?
> The simulation is one of many I am playing around with. This
> particular one tries different wire sizes and coil heights to maximize Q
> with several constraints:
> 1. primary surge impedance = 30 ohms (fixes Cp and Lp, since Fres is known)
Fres being?
> 2. secondary surge impedance between 25k and 35 k ohms.
> 3. make the wire length close to the operating 1/4 wavelength.
> These parameters are based on the experimental observation that
> several excellent coil systems I have studied all have these common factors.
> When I plug in your 7 pF top capacitance with 6.6" diameter, it says to wind
> the coil 10.5 inches tall using 22 AWG wire, which is probably a bit short,
> if you want to keep the thing from arcing down its sides. To compensate for
> the short coil, you need to add more top capacitance according to this
> model. The program suggests that one should use a coil height of around
> 18.5 inches with 14 pF of top capacitance, using 22 AWG wire. An even
> taller coil would need more top capacitance. You can either try your coil
> with some more metal on top (raid the kitchen for pots, pans and metal
> bowls), or suggest a better constraint for this model! The high top
> capacitance is typical for some of Richard Hull's coils (55 pF on his 14"
> diameter Nemesis coil). If you can achieve breakout, you get really long
> sparks. Wire sizes of 21-23 AWG maximize Q for coils operating at these
> frequencies. (The program tries all AWG wire sizes from 4 through 40.)
> Note that by constraining the surge impedance of both the primary
> and secondary, I am essentially fixing the secondary voltage rise to around
> 34 times the primary voltage. This is a tradeoff, but appears to yield nice
> long sparks.
> The matching of the quarter wavelength was discussed at length on
> the list a while ago. Skip Greiner has a spacewound coil that has a H/D of
> 1.37. It is wound to match quarter wavelengths, and it really puts out long
> sparks. I still don't have a good reason to follow this practice except
> that several coils I have built also work nicely with this constraint so why
> not! In addition, coils with a H/D of around 3:1 closewound with the
> correct wire gauge and large top capacitance seem to naturally resonate
> close to the 1/4 wavelength. (Let's not discuss this again on the list
> right now!)
> Regards,
> Mark S. Rzeszotarski, Ph.D.
Yeah I know :) Well, Skip is running a sync rotary which plenty of
evidence suggests is the best type of gap and the resonator is rather
large (lot of C). I'll try the bigger topload on both coils when I
next have a working power supply. I should really measure the Q's
also. They are pretty high judging by a quick frequency sweep I did.
Got to get into sync mode as well.
While I'm thinking about it, what seems to be the ratio of neon
deaths in single transformer running vs paralleled transformer
running? Anybody/all?
Thanks,
Malcolm