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Re: Primaries
Tesla List wrote:
>
> >From MALCOLM-at-directorate.wnp.ac.nzSun Sep 22 22:33:43 1996
> Date: Mon, 23 Sep 1996 09:28:17 +1200
> From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
> To: tesla-at-pupman-dot-com
> Subject: Primaries
>
> Hi all,
> I have some questions I would appreciate some answers to.
> (1) To Greg Leyh : You mentioned some figures for gap current and
> gap conduction voltage the other day. How did you measure those?
> (2) To Richard Hull : Have you tried primaries with v. large L/C
> ratios (for example, L of 200uH+). If so, how well did they work?
> Was there any improvement over say 100uH? I am assuming that
> the bang size and break rate was kept constant.
I have used some large primary values, but none so high as 200uh!!
(110uh is my largest) I would be curious myself to check this out. If
you go way up in primary inductance you can reduce the cap size and run
huge break rates. R. Hull
> (3) Also to Richard : Have you _ever_ measured a dynamic primary Q
> above 10?
I have never concerned myself with primary Qs and have never measured
same. We traditionally want a grossly coupled primary anyway, and the Q
is naturally going to nose dive into the crapper anyway. R. Hull
>
> I have desgined and am construction a low frequency secondary for
> a number of different experiments, several different types of systems
> and also to have a crack at setting a record for around 2.3kW. I am
> constantly running into a barrier with the primary and in particular
> the gap losses. It seems that this is almost the sole determining
> factor of system performance and I am desperately trying to find a
> way to improve it without resorting to exotic devices. For your
> interest, resonator spec is:
> L about 140mH
> Cself around 24pF
> Winding Height 39"
> Diameter 16.5"
> Closewound with 0.9mm diameter wire
> Former = open frame (simply because I don't have any pipe).
> Predicted Fself around 87kHz
> Predicted F with around 45pF topload about 50kHz with a range
> of frequencies in between for smaller toploads.
>
> I am currently constructing the former which is turning out to be
> a tricky exercise with the materials I have on hand.
> An analysis based on a dynamic primary Q of 10 suggests that the
> lower in frequency I go, the smaller the gap losses become.
> If anyone has any input on this or comment to make I would
> welcome it. I am just about at the end of the rope with regard to the
> primary. I had hoped late last week that gap losses might reduce with
> a drop in gap current but it seems that hope is doomed.
>
> Malcolm
Malcolm,
Sounds like a killer system!! I will be most curious how it turns out.
Richard Hull, TCBOR