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Re: Plans for a 7.5 kv coil
Tesla List wrote:
>
> Original Poster: Dale Baranowski <rabelais-at-actcom.co.il>
>
> I confess that I'm new to this list, having
> signed on just a few days ago, and my usual
> habit is to lay in the shadows for a coupla
> weeks before submitting. However this time I
> decided to make an exception because I need a
> project to work on with my son and winding a
> tesla coil seems like a very good option.
>
> I've got a background in electronics, having
> earned my ham radio liciense 30+ years ago in
> high school and built my own transmitters
> from scratch. About that same time a friend
> and I made a tesla coil which spit sparks 25"
> long. So I'm not a stranger to either HV or
> RF.
>
> My son and I would like to build a coil and
> I've scoured the internet for plans, found
> some interesting websites, but the majority
> of examples and plans I've seen utilize neon
> sign transformers at 15 kv or higher. I have
> one neon sign transformer that's a 7.5 kv and
> a number of fuel-oil burner ignition
> transformers which are also 7.5 kv. I know
> that it is suggested to go to a store that
> deals in making neon signs for advertising
> purposes but I live outside of Jerusalem,
> and though Israel is definitely not a
> 3rd-world country, small neon signs are just
> starting to be visible in this country. I'd
> be hard pressed to locate such a shop, much
> less obtain one bigger than 10 kv in any
> case.
>
> So can anyone direct me toward plans that
> might use a transformers that I have in
> stock, rather than attempt a possibly futile
> attempt to ferret out one of a higher output
> voltage?
>
> Any help that could be provided would be
> greatly appreciated.
>
> Dale Baranowski
Dale,
Smaller coils can be made to work quite nicely with 7.5 kV transformers,
and making or finding tank capacitors is often a bit simpler when
running at a lower voltage. You should be able to drive a 3"-4" diameter
coil quite nicely. Most Tesla Coil design programs will allow you to
design a system starting with input voltage and current from your neon
sign transformer (NST) and Oil Burner Transformers (OBT) - the output
power can be increased by connecting them in parallel. This will govern
the maximum size tank capacitor you can drive. The product of the
primary inductance and capacitance (LpCp) must equal that of the
secondary self-C and topload terminal capacitance (Ls*(Cs+Ct) to
maintain tune - this will let you adjust parameters of the primary and
secondary (play "what if" using the design tool) before committing to
actually build the coil. Go to the archive site at:
http://www.velocity-dot-net/~djb/files.shtml
and download some tools - Wintesla, Tesexla, or TCCAD are all quite nice
- pick the design aid that you like best. Also, both you and your son
need to check out the safety sheet (and other maybe browse/search the
archives at Chip Atkinson's site: http://www.pupman-dot-com/
The other text files will cover some of the elements of the system - for
example to cover construction of tank caps, static spark gaps, toroids,
secondaries, etc, check out the various text files at the same archive
site. Use the Tesla coil design program to "rough out" the design, and
the text files to provide specific construction hints/details for
building the elements of YOUR coil. Half the fun is in taking every day
items and applying them instead to parts of your system. Hunting these
items down is often quite an interesting challenge! You've already
conquered one tough part - getting HV transformers. Finally, if you
still have questions, come back to this forum and we'll be glad to help!
Good luck, and safe coilin' to you and your son!
-- Bert --