[TCML] Is my understanding correct?
Gary.Lau at hp.com
Tue Sep 16 18:32:13 MDT 2008
1) Desirable Freq, (high or Low) to give the caps an easier time
Lower frequencies are generally easier (have lower losses).
2) Prim Inductance, High or Low to get down gap losses, come to that, what
is High or low on a coil this size ? ? ?
Higher primary inductance yields lower gap losses. I'm not sure how to suggest actual values.
3) Aspect ratio: (4 to 5:1 I know that) BUT one design (the lowest at 181)
uses a 5.5:1 - is this ratio pushing it a bit?
This is another thing that is by no means cast in stone. 5.5:1 is by no means extreme; I think that if it gives a higher pri inductance, go with it.
4) Can a 10K/48ma NST power a 4.5 inch coil (as opposed to the norm of a 4
inch for this NST)
Another example of things that are should not be cast in stone. I personally think that it's more important to observe an ill-defined minimum secondary size as a function of transformer VA, just so that a tiny secondary isn't swamped by sparks. I used a 4.5" dia secondary on my 4kV/20mA powered coil, and it was the best thing I ever did for it.
There probably is a maximum secondary size for a given transformer VA rating, but it may be that the coil would be awkwardly large before that point is reached.
Regards, Gary Lau
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of P Tuck
> Sent: Tuesday, September 16, 2008 6:08 PM
> To: tesla at pupman.com
> Subject: [TCML] Is my understanding correct?
> JavaTc is a great tool, but the trouble is you can play around just a little
> 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 & mill
> 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 to
> 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 181)
> 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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