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Re: Primaries
Malcolm
I tried an experiment with a multiple point rotary gap a few weeks ago.
There was a very slight
difference between 1 point and 3 points (52" vs 56" streamer). I haven't
been able to
test this again. There are many variables in the setup that cannot yet be
excluded.
The gap also ran rougher with 3 parallel points.
Barry
----------
|From: "tesla-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|To: Benson Barry; "Tesla-list-subscribers-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|Subject: Re: Primaries
|Date: Tuesday, September 24, 1996 10:41AM
|
|<<File Attachment: 00000000.TXT>>
|> Subject: Primaries
|
|From bert.hickman-at-aquila-dot-comMon Sep 23 22:15:37 1996
|Date: Mon, 23 Sep 1996 07:14:50 -0700
|From: Bert Hickman <bert.hickman-at-aquila-dot-com>
|To: tesla-at-pupman-dot-com
|Subject: Re: Primaries
|
|Malcolm,
|
|Good luck on the new coil! A 45 pF topload on top of a 16" diameter coil
|should make for a pretty good sized coil for a 2.3 kW system! Re: gap
|losses - it seems like nature and physics has conspired to limit primary
|Q. The negative resistance characteristic of the gap arc is a fortunate
|phenomenon(!) - think of the losses if it had a positive characteristic!
|Unfortunately, it seems that whatever current primary current levels we
|run, the arc compensates (and limits us) to a primary Q of 10-12.
|
|One way to improve the system efficiency would be to maximize the
|coupling coefficient so that more energy transfers to the secondary
|quicker, reduccing the duration of the gap losses. If we can succeed in
|quenching the gap immediately after the first energy transfer, we've
|should maximize power transfer. With a 2-coil system, this is probably
|"practically" max'ed at k=0.22. If you're able to hit higher "magic" k's
|without breaking down the secondary or flashing to the primary, AND if
|you can quench the gap, you should be able to break 2-coil records.
|Otherwise it looks like a maggie is the only way.
|
|Good Luck!!
|
|
|-- Bert --
|
|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.
|> (3) Also to Richard : Have you _ever_ measured a dynamic primary Q
|> above 10?
|>
|> 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
|
|