Re: first coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


The basic laws of electrical circuits still apply, even Ohm's law has an
effect on RF currents.  If you are trying to stuff 200 Amps through a 12 AWG
wire it will retard the current somewhat even if the time period is measured
in microseconds.  It's the current that is responsible for creating the
magnetic field, not the potential.

Dan may have the same output potential but if he measured the current in the
output I'm certain he would have noticed a decrease in the secondary current
with the smaller wire.  We did a similar experiment many years ago and used
4 sec. shots of the discharge spark in a dark room.  The smaller wire has a
much less brighter output spark than the larger wire even though the sparks
had approx the same length.  They were noticeably thinner but only to the
camera -- not the naked eye.

Bill Wysock and I did a similar experiment back in the early 80's.  Bill
rigged a large coil to trigger a huge capacitor to discharge into the
streamer in an attempt to produce a fat, thick spark.  To our eyes and ears
we couldn't tell the difference, but after the film was developed, the huge
fat 3 inch dia. discharge was present.  It didn't sound any louder or seem
to us to be any brighter but the picture told the story -- it was very fat
and thick.

Even though the pulses are there for a short period of time, during those
short periods of time in a small gauge wire the current pulse is going to be
somewhat reduced by the resistance of the wire. In a series circuit whatever
element that has the most resistance will limit the peak current that can
pass through the circuit.  Why not error on the side of least resistance?
Lost performance will never be missed by anyone of doesn't know it's lost.

We use 4 AWG wire on all of our NST powered coils.  This is somewhat
engineering overkill, but I would say that you should use at least 6 or 8
AWG for your primary wire.  12 or 14 AWG isn't good engineering practice
just like running a MMC cap at it's rated DC voltage is pushing your luck.
Why waste an evening trying to figure out which cap died when you don't have
to?

Overengineer a bit -- it's good for the soul and you make the electrons very
very happy.

Dr. Resonance

 >
 > Sorry Nolan, I disagree.  12 AWG wire will work perfectly fine with a
 > 15kV/60mA.  In fact, a year ago I performed a test in which I would
compare
 > output of my
 > 15kV/60mA coil with using 4 AWG stranded welding wire (the orange stuff),
 > and using 14 AWG HV wire.  In both tests, I got exactly the same output
from
 > my coil.  There was no difference period!  Now if you were using 12 or 14
 > AWG wire and your wire lengths were like 5 feet plus, then thats
different.
 > But if you keep your connections as short
 > as possible, 12-14 AWG wire will work fine with no decrease in
performance.