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Re: Tesla Research Possibilities




From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: 	Tuesday, September 16, 1997 5:46 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Tesla Research Possibilities

In a message dated 97-09-16 02:49:20 EDT, you write:

<< From: 	Pete Demoreuille[SMTP:pbd-at-cybernex-dot-net]
> Sent: 	Monday, September 15, 1997 7:27 PM
> To: 	tesla-at-pupman-dot-com
> Subject: 	Tesla Research Possibilities
 
> All -
>	This year I have the opportunity to do independent research
> as a class in school.  Being very interested in Physics, Math and
> the like, I hope to be able to do further research into the several
> Coils that I have built.  I am hoping that some of you have some ideas
> that you could share with me, or could give me comments on some of the
>design ideas that I have listed below.  I hope for this to be original
> research - hopefully I will be able to enter this project as a
> Westinghouse project - but it must be original and at least somewhat
> applicable to the real world - no matter how small.

Pete,

This sounds like a great opportunity.
 
> I was wondering about several things.  Why is the accepted standard
> of turns in the 400-1200 range?  Is there a rationale??  Why hasn't
> anyone ever made a coil with many more turns, i.e. 3000+.  If making
> the coil have a desirable aspect ratio is such a problem, then use a
> thinner wire, and to make higher currents possible in the coil you may
> use multiple layers wired in parallel.  (and does aspect ratio really
> matter *within reason* in resonator coils or base fed coils???)
> With a secondary with many more turns, wouldn't it be possible to
> greatly increase the pri/sec coupling without having to worry about
> interturn breakdown - because there are so many more turns, the 
> interturn voltage rise would be bearable.

Most of the energy seems to couple into the lower part of the coil,
in such a way that interturn breakdown will occur at tight coupling
no matter how many turns are used.  I've found that using fewer
turns, and thicker insulation permits a higher k to be used, although
I am presently using quite a few turns, but relatively loose k.  The
real key to preventing secondary breakdown at tight couplings, is
to make sure that the gap quenches well...this is the greatest
challenge.  It seems that a good spark-gap can do only so much 
to ensure good quenching, optimal quench seems to depend
largely on proper output spark loading.  There is much work to
be done in the area of optimal quenching and spark loading.  The 
gap is in many ways the heart of a TC, but loading is also of
critical importance.

Narrow secondaries do not seem to work as well as wide ones in
a disruptive TC.  If the coil is too short, sparks will jump from the 
top of the coil to the primary.  A reasonable aspect ratio may give a
higher Q
 
> Also, relating to efficiency.  Has anyone ever tried other primary
> designs?  i.e. not just flat and helical, and ones with a constant
> slope, but ones with a constantly increasing slope, in order to make
> a more desireable field and completely 'immerse' the coil in the field,
> making voltage rise occur over the entire coil - not just the bottom
> half.

There has been some discussion on the list a while back discussing
possible merits of different primary shapes.  But no consensus 
emerged.  In theory, perhaps some shapes may be better.  More
research is needed.
 
> ** many many questions coming - be warned  **
> Has anyone ever done research into why the color of the sparks are what
> they are - i.e. purple when they terminate in the air, and white/blue
> when striking an object.  I know that glass is supposed to give purple
> spindly sparks - but why?? the rate it discharges at?  its higher 
> dialectric constant??  What do caps of Barium whateveritis do to
> spark color?? why are caps with a higher dialectric constant less
> efficent when operating at RF??  why do secondary coil forms with
> a thicker wall cause more RF loss??

I think the color of the spark indicates the energy in the arc.  But I'm
not an expert on arc colors.  Others may have more insight into this.
High break-rates, and/or high frequencies, seem to produce a plasma
like spark.  High break-rates create a frantic spark that jumps around
quickly, low break-rates produce a more slowly wavering spark.

If a coil form is made from a lossy material, and is thick, there will
be more material to heat up due to RF heating, therefore more 
energy will be "stolen" and prevented from going into spark production.
I once made a large lossy cardboard coilform that ran quite warm
in a vacuum tube coil, and gave terrible performance.  I've used
barium titanate caps and the sparks appeared nice and blue/white.
 
> Wow.  I think I exhaused my questions for the moment -

I think it would be interesting to research the effect of high-break rate 
and small cap, vs. low-break rate and large cap.  (small bang vs. large
bang.  Another interesting area is the study of losses in the ballast
and transformer at various break-rates.  A true wattmeter such as
Dave Sharpe's opto-isolator wattmeter would be needed because
of the spikey, distorted 60Hz (50Hz) input waveforms.
 
> THANKS ALOT FOR ANY INPUT!
 
> Pete Demoreuille, Delbarton School
 
> ps:  one more - what kind of amperage is entering the coil from ground?
> And exactly why does the amperage convert from AMPS at the bottom
> of the coil to potential at the top??  The secondary is for the most
> part DC?  shouldn't current be constant?? 
> (last one i promise) :)

I'm not aware of any DC in the secondary coil.  

John Freau