[TCML] Is my understanding correct?
resonance at wildblue.net
Tue Sep 16 20:51:53 MDT 2008
If you are going for 3-4 ft sparks, you will need a lot more current than 48
mA. Probably 120-250 mA range. Lots of NSTs
in parallel work fine.
More capacitance is used for lower resonant freq, and more capacitance
equates directly to more energy per shot.
Larger capacitance requires more current for rapid charging. All of this
usually produces longer sec sparks.
With NST type coils, usually 10-14 pri turns is about right. Adjust
capacitance to match res freq in javatc.
I use 4.5 to 1 h/d ratio, but even 5.5 will work ok.
Use the largest possible sec coil dia --- I use 6 inch or even 8 inch for
nst coils. If you use a Sonotube it remains
very light even with 8" ID tubes. This helps a lot especially if your are
limted to under 100 mA on your xmfr current.
More inductance produces more potential and the inductance goes up as the
SQUARE of the radius of the coil.
Vsec = -L x dI/dt
On Tue, Sep 16, 2008 at 4:07 PM, P Tuck <follies at ntlworld.com> wrote:
> JavaTc is a great tool, but the trouble is you can play around just a
> bit too much! For newcomers, like myself, that can be a headache.
> In my case the archives have given a wealth of info on building tips, and
> 'desirable' qualities that I "think" my first coil should have, allowing me
> to come up with 4 differing designs in JAVATC.
> I'm using a 10K / 48ma NST with CD 942C20p15K caps ( LTR - 0.02143 uF) both
> of which I have already got. Also a static single gap (I have a lathe &
> etc so it will be hollow electrodes either sucking or blowing with a vacuum
> cleaner motor as in the recent posts on that subject)
> My quandary is that using a 4 inch coil and depending on what design I
> adopt, I can achieve between 181 to 236 KHZ Res Freq with differing
> Inductance values.
> The 236 freq' would have a Primary of 20.5 uH and the 181 would work out
> 35 uH - a considerable difference. Both have a Q around 255 (260 & 247) so
> not much to choose from there.
> As I understand things a lower freq and higher Prime Inductance are better
> if you prefer a solid discharge (I'm only in the 2 to 3 foot range - I
> realise that) rather than lots of 'bushy' sparks.
> My other 2 designs fall in between these extremes.
> All the designs use either AWG 26 or 28 and all are in the 1000 to 1500
> turns range.
> But.......IF the NST is suitable for a 4.5 inch coil I have a 5th design
> where I can get a slightly lower freq (162) and a slightly higher Pri and
> Sec Inductance.
> Obviously everything is a trade off, one 'desirable' quality against
> another, but what qualities should I really be the most concerned about
> aiming for, using a modest sized NST?
> Some points to bear in mind are:-
> All coupling Coefficients are around 0.12 to 0.13 and all the recommended
> primary distances to sec' coil are acceptable
> Longer run times are favoured against shorter ones
> So finally my Questions are:-
> 1) Desirable Freq, (high or Low) to give the caps an easier time
> 2) Prim Inductance, High or Low to get down gap losses, come to that, what
> is High or low on a coil this size ? ? ?
> 3) Aspect ratio: (4 to 5:1 I know that) BUT one design (the lowest at
> uses a 5.5:1 - is this ratio pushing it a bit?
> 4) Can a 10K/48ma NST power a 4.5 inch coil (as opposed to the norm of a 4
> inch for this NST)
> Thanks hopefully in advance
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> Tesla at www.pupman.com
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