Ignoramus27736 wrote:

On Wed, 19 Oct 2005 23:20:50 -0500, Don Foreman wrote:


On Thu, 20 Oct 2005 03:46:27 GMT, Ignoramus27736
wrote:



Made a 1/4" spark gap... I see sparks... Very exciting...

http://igor.chudov.com/projects/High.../Franceformer/

i


That's a neon xfmr. Three of those in series should make a dandy
Jacob's ladder!



Sounds interesting. I have 13 of them today. Maybe I will get more
tomorrow. I forgot to pay for all the stuff I got today (and the owner
forgot to ask me for money) and need to go there tomorrow to pay
anyway.

Sorry, I digress.

I am confused by different statements made by different posters. Some
say that they cannot be set in sequence because they are center tapped
to ground. I am not so sure, since they can be mounted in
isolation. Who to believe?



The buzzzzzzzZZZAP noise it makes adds to the fun.



Yes. I just tried something interesting. I tried blowing at it. It
made some big arcs and a corona discharge. Tomorrow, I may try to blow
argon at it from my tig welder.


Try quickly pulling a piece of typing paper through the arc. Do it fast
enough that the paper doesn't light and you will see perforated holes
showing that the arc is not continuous as it appears....after all, it is AC.

Koz (who did this as part of the science demos also....Kids have no clue
that AC from your wall socket is not the same as DC from a battery)




With 3 or 4 of them in series, a Jacobs ladder should be able to
sustain an arc over an inch long before it goes out at the top and
starts again (ZAP) at the bottom.



Very nice.



The nameplate ratings can be confusing. They deliver rated voltage
under open circuit conditions, rated current at short or near-short
conditions. Once a spark/arc is initiated, voltage drops to about 1KV
in a short gap. 1KV is a near short condition for a 30KV xfmr.



Well, sure, that's what constant current stands for, more or less.



A job I once had was designing electronic oil ignition xfmrs, 30KV at
30 mA. They ran at about 30KHz. In normal use the rectified AC
wasn't filtered -- but if a filter cap was added, the arc/spark was
eery quiet -- just sort of a soft hiss. A Jacob's ladder with that
was like the audio was missing.



The nameplate does not actually say what the output current is, AC,
DC, HF, etc. I think that midpoint grounding pretty much implies
AC. Not sure if it is 60 Hz or HF. My guess is that it is 60 Hz, both
from the buzzing sound as well as the weight of this franceformer.

i