Outdoor performance problems
From: Robert W. Stephens[SMTP:rwstephens-at-headwaters-dot-com]
Reply To: rwstephens-at-headwaters-dot-com
Sent: Sunday, January 11, 1998 5:56 PM
To: Tesla List
Subject: Re: Outdoor performance problems
> To: "'Tesla List'" <tesla-at-pupman-dot-com>
> Subject: Outdoor performance problems
> Date: Sun, 11 Jan 1998 13:52:45 -0600
> From: Tesla List <tesla-at-pupman-dot-com>
> From: Jeff W. Parisse[SMTP:jparisse-at-teslacoil-dot-com]
> Sent: Sunday, January 11, 1998 10:50 AM
> To: Tesla List
> Subject: Re: Outdoor performance problems
> >I had my coil running really well indoors (snip) and when I put it outside
> (38o F, moist) I got some puzzling problems
> >Seems like temperature was affecting something.
> The moisture in the air, not the temp, was causing your sparks to be
> shorter. Moist
> air is more conductive than dry air and therefore sparks dissipate faster in
> a moist,
> conductive environment.
> I've seen tapes of Robert Stephens on very cold (yet dry) Canadian winters
> his coils with tremendous results.
> Jeff W. Parisse, Director
> kVA Effects
Adam, Jeff, All,
I just have to jump in here and respond to set the record straight.
In my own experience, and this has been proven by dramatic
demonstrated results, both indoors and out, many many times over, that my
disruptive TC's produce their greatest streamer length when the humidity is very,
very high and is like you see sometimes, just swirling around in the
air as a mist of microdroplets. Yes it's absolutely true!
Jeff, it is true that my big coil being run at -20C in very dry
Canadian winter outdoor air on the videotaped test you saw was really
kickin' butt. However the truth is
that the streamers would have been another 20-30% longer still on a
humid summer night, all other parameters being equal including power
input! Air density plays here as well and cold winter
air is harder to ionize than warm less-dense air. Think about it.
With a mechanical vacuum pump connected to a glass tube with
electrodes connected to a high frequency, high voltage power supply
(a plasma globe is a perfect example), as the air pressure is brought
down from atmospheric (density continuing to drop) it take less and
less voltage to ionize the space between or around the electrode(s).
A dramatic difference can be seen between dense winter air and less-
dense summer air. Note that at a pressure near the bottom limits of
what a good mechanical roughing pump will obtain the ionization
phenomenon starts to reverse and there become too few gas molecules
to sustain ionization and the vacuum starts to become a good
insulator. Devices like vacuum capacitors contain an excellent
*hard* vacuum and are very, very good in the voltage leakage holdoff
Unfortunately there seem to be other factors which cause many
coiler's devices to produce spark lengths that vary on
different days which can make this *spark-length to humidity and
temperature* function obscure due to system instabilities from myriad
other causes. Like any other area of research, you can't measure distance
with repeated accuracy with a rubber ruler. I've seen discussion on
this before from time-to-time and it seems there are enough differing
results posted to confirm my observation that there seem to be quite a large
number of *rubber* Tesla coils out there.
Let me say this again. I have NEVER seen any correlation to
increasing humidity with a disruptive Tesla coil that I have built other than to
witness an INCREASE in streamer output length at the same time.
Tesla coils built with insulating materials which are hygroscopic in
nature however would likely see a decrease in performance as absorbed
moisture tended to reduce the insulation ability of system components
such as the secondary resonator. Coils wound on cardboard formers
would be especially prone to such losses. After that, even with good
non-hygroscopic materials, once the moisture becomes condensing however,
and your insulation begins to get compromised by surface leakage
currents through the deposited moisture mixed with deposited dust
which can contain conductive salts, etc., this rule will obviously fail.
My phased twin TC is set up permanently to entertain visitors to my
lab to a wall-to-wall lightning show. In the dead of winter I can
ALWAYS get the unit to give the same awesome show at lower power if I
increase the room humidity by closing all the doors and boiling kettles
for an hour in advance. The 15KV-at-60 mA neon xfmer powered coil also
demonstrated perks up very nicely as well, hitting up to 52 inchers
in the increased humidity.
Maybe coiler's should be buying electric kettles (apparently dual-use
technology) as opposed to arc welders to use as pole pig ballast devices! : )
Just kidding actually. I've had much higher performance from the use
of inductive power limiting than resistive as the inductive can be
employed to give resonant charging advantages based on spark gap
closure rate as opposed to pure power waste through straight
resistive ballast schemes.
Keep your coil dry and your air humid.
Robert W. Stephens
Lindsay Scientific Co.
RR1 Shelburne, ON Canada L0N-1S5
Tel: 1-519-925-1771 Fax:
*Custom built Tesla coils, etc., for museum display
and special effects work.
*Canada's largest publicly accessible wall-to-wall
indoor lightning show...by appointment.
*Future home of Electric Science World,
educational/entertaining Theatre of Electricity.
~~~~~~~~~~~~~ Inquiries welcomed! ~~~~~~~~~~~~~~~