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Re: NST Conundrum(s)
Hi Robert,
My comments are interspersed. I hope they help to
"unstump" you ;o))
>Original Poster: "ROBERT CRESSLER" <59CREROB-at-menasha-dot-com>
>This is probably has a obvious solution but it is not apparent to me. Two
>things
>1) I have 4ea 15kv/60ma all difference makes &models I checked the
>resistance of the secondaries and no two were even close ... I do not
>have the exact numbers... but some were different by a factor 2 (for
>example 318,224,178,ect......) why?
This depends on xformer construction. The voltage is dependant on
turns ratio and the current on core design and wire gauge. While the
turns ratio will be roughly the same for all 120V to 15kV xformers,
namely being 1:125, you can achive this ratio in many different ways,
like:
a.) 1 turn on the primary, 125 turns on the secondary.
b.) 300 turns on the primary, 37500 (really 2 x 18750) turns on the secondary.
Of course both cases are exaggerated (sp?) examples, but you get the idea.
The DC resistance will be quite different from case "a" to case "b", yet both
will supply you with 15kV (core saturation will prevent this in case a, but
that isnīt of importance right now). Every xformer manufacturer has his
"ideal" idea of building a transformer. The AWG for the secondary should
be approximately the same (truely depending on built-in overdesign) in all
cases.
>2) I have tried to co-phase by paralleling and then and reversing to see
>which arc is longer,but am not able to discern a significant difference in
>arc l length....??? yikes! 3 not 2..........3) any problem if I series the
>primaries of a pair so I can supply with 220v?
"In-phase" paralleling them will give you more current, whilst out of phase
will give you more voltage (and probably a dead NST :o[[). You can series
the primaries (for a higher input voltage and less total primary current draw,
being roughly the same as a single NST connected across 120V) and
parallel the secondaries for a higher output current. If you exchange your
present single xformer setup with a 2 or 3 NST setup, you wonīt necessarily
get a longer spark output (I gather you mean the TC output). Depending on
your cap and gap setting, the Joule amount doesnīt increase. Your breakrate
might, tho. What you have done is increased the maximum cap size your
xformer can charge. For longer sparks you will now need to increase your
primary cap (and discharge toroid). Following John Freauīs equation you
should be able to increase the output spark length by a factor of 1.73,
now using 2700VA in (3 NSTs) vs. the old 900VA (1 NST).
Coiler greets from germany,
Reinhard