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Re: TC Limits
Tesla List wrote:
>
> Original Poster: "Ruud de Graaf" <rdegraaf-at-daxis.nl>
>
> >Original Poster: "Mark Fergerson" <mfergerson1-at-home-dot-com>
> >
>
> snip...
> >Most commercial speakers are pure crap IMHO. I guess we're lucky
> >nobody makes TC's commercially, eh?
>
> Actually they do! Look at http://www.amazing1-dot-com/tesla2.htm for 'the
> smallest Tesla Coil'.
I might have known Information Unlimited would be in on it...
> >> For a pulse mode 50KV supply I think you could best search on the net for
> >> "laser power supply" or "Sam's laser faq".
> >
> > I bookmarked Sam's site some time ago. I was looking at a TC because
> >I want to build as much of this thing as I can, and I don't need a
> >whole lot of output current. A TC is such an elegant thing, so few
> >components for so much results.
>
> Yes, it is so elegant that 'the smallest TC' I mentioned delivers 75kV (they
> say)! That's why I don't understand your 50kV limitation. Heck, on a sunny
> dry day you could build that up in seconds, just by walking!
The application I have in mind is an accelerator; the 50 kV will be
applied to each stage simultaneously for a total of 500 kV. I want to
avoid arcing etc. so I decided to keep the subsystem (TC etc.)
voltages as low as possible. The whole thing will be fairly small
except for the actual accelerator.
> > I keep getting told that "certain things won't work" without any
> >justification. I hate that and wanted some ideas from experts who, if
> >they haven't done what I'm talking about, can at least tell me _why_ I
> >shouldn't bother. Most electronic systems scale nicely (with some
> >adjustment, of course) and a TC should, too, no?
>
> In theory maybe, but if you only consider the spark gap, it will be clear
> that growing from a single to a multiple to a rotary gap brings a lot of
> different problems to solve.
I'm looking at using a series-parallel array of Xenon tubes with
magnetic quenching (large permanent magnets) for the spark gap, and
since they are already erosion-resistant and designed to be triggered
externally they seemed perfect (I just have this silly personal bias
against moving parts in an electronic system). I'll be using digital
timing to get the pulses to appear when the accelerator needs them. I
want synchronous excitation of the secondary; starting the primary arc
in synch with the already present waveform on the secondary so I don't
get out-of-phase energy "fighting" the ringup. That seems impossible
to do mechanically.
> > Details like how to determine the coupling between coils before
> >winding them should be straightforward from geometry, but I don't know
> >how, and was hoping somebody could give me a clue.
> >
> Coupling is depending on geometry, so experimenting is for the most of us
> less demanding then finding the wright formula...
Well, I'd like to be "close" when I build the thing, so I have less
to fine-tune.
> > My question about length/diameter ratio was prompted by an offhand
> >response from sci.physics.electromag; I've since gotten a more
> >detailed private reply that cleared some of it up for me.
> >
> Ok, you made me curious. How private could this info be? Let's share our
> wisdom!
Dan Kline kindly sent me a private e-mail with the mentioned
clarification. With his permission (Dan, you listening?) I'll post the
relevant section here. I get the feeling most of you here already know
what he wrote me, though.
> > As for my question about frequency limits, it relates to how often I
> >want an output pulse, and I established 1 MHz as a starting point only
> >to be told "no go" again without justification. That, and I'm curious
> >about how small a TC can be built and still work "satisfactorily".
> >
> That's also a point of interest for me. I think there are contradictory
> influences.
> I think for an air coupled core, the higher the frequency the better the
> energy transfer to the secondary coil, but the higher the frequency the
> lower the capacitance of the primary cap must be (else, out of resonance).
> But the lower the capacitance of the prim. cap the less Joules and the less
> Joules the smaller the secondary arc!
That's what I thought, too. Without going to something besides air
for the core, I couldn't figure out how to keep the power transfer up.
Ferrites are OK, but suck too much power as heat. I'm collecting those
little strips of hi-mu metalglass that are used in the US as
anti-theft devices on grocery products (for use as a high-frequency
core), but I can't find any data on their likely hysteresis
characteristics.
> Anabody out there who can help with this one?
Please?
> > Maybe I'm just too lazy, but I want to eliminate certain design
> >options as "bad" without having to build them first. I also want to
> >know why just for the sake of knowing stuff, I guess. That may be a
> >conflict I'll have to resolve with a soldering iron; I should bestir
> >myself and make a contribution somewhere. If nobody else has explored
> >this area yet, I may discover something interesting...
> >
> I think you hit the nail here! That is partly the reason it stay's
> interisting to make a TC. Someday you could get the credit for an important
> improvement. It will only be known by 700+ man and woman and will not save
> lives in the 'real world' or improve the 'quality of life', but it will
> help.
I've enough trouble improving my _own_ quality of life; I try to
stay out of other people's but I'll be happy to post any advances in
the art that don't kill me ;>)
This will be my second stab at building one. My first was nearly
thirty years ago. A "standard" design; four foot tall secondary, NST's
and a static air-blown gap. Got good sparks, but kept blowing
breakers. It was "donated" to a nephew who I've since lost touch with.
Mark L. Fergerson