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Re: Safety gap issues



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

JT, you're not listening. I said you can ONLY use 30KV/cm and a meter stick to calculate breakdown if it is a UNIFORM FIELD. This is rarely the case unless you have two parallel plates where the plate separation is small compared to the size of the plate. The 30KV/cm is a field strength the the air molicule experiences. This field strength may be present only in a very localized volume.
Gerry R.

Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

You said:
"The breakdown for air is approximately 30KV per cm. This is a local field strength and if the field is uniform (constant) then you can measure the distance to find the total breakdown. The 25KV per inch you found probably assumes a geometry and applies to a short range of distances. "
Well holy crap, that throws ALL my measurements with high voltage 
off a lot. My sparkgap for example is set at 7.5 to 8 mm. That means 
my sparkgap is set at 22.5kV? NO WAY; MY TRANSFORMER OUTPUTS 12KV 
ONLY. SO, IF IT WERE SET AT 22.5 KV, IT WOULDNT FIRE WORTH CRAP.
THIS MEANS THE FORMULA:  1cm=30KV   cannot be correct

Thanks a ton for the help, but I THINK you're wrong buddy



From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: Safety gap issues
Date: Fri, 25 Nov 2005 08:00:02 -0700

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi JT,

Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

Use a counterpoise? You mean putting large amounts of al foil, spread on the ground, as an RF ground? WTF no way dude, that ruins the aesthetics of my coil.
Counterpoise was for indoor operation.  If you are outdoors and 
have a rod in the ground, GREAT.  Keep the NST with the coil and 
ground the NST, secondary base, and strike rail to a common point 
and run a heavy short wire between this common point and the pipe 
in the ground (RF ground).
Your target for sparks should be grounded to RF ground at the 
common point (not the pipe end).  This keeps strike return current 
out of the heavy wire to the pipe and will help keep RF ground 
noise to a minimum.   Ground your variac and line filter to mains ground.
The breakdown for air is approximately 30KV per cm.  This is a 
local field strength and if the field is uniform (constant) then 
you can measure the distance to find the total breakdown.  The 25KV 
per inch you found probably assumes a geometry and applies to a 
short range of distances.
Gerry R.


i DO have a 4 foot Cu pipe driven into the ground, and 15 feet of wire is attatched to it. *I use this separate ground as a ground for the sparks to jump to.(from toroid directly to this)
*I have read all over, 1 inch requires around 25,000 volts to make 
a spark connect. So, i have been measuring EVERYTHING using this 
equation. IN OTHERWORDS, I USE 1MM=1000V. My sparkgap is set at 
7.5 to 8 mm, thus 7.5 to 8 kV
* my output is 15.5 inches- so i times that by 25,000 volts per 
inch- to achieve a staggering
388KV tesla coil output

I HOPE YOU GUYS CAN UNDERSTAND EVERYTHING I JUST TYPED!



From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: Safety gap issues
Date: Thu, 24 Nov 2005 10:38:19 -0700

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi JT,

An unloaded NST is with no load attached to its output. 12KV is an rms voltage which means that peak voltage is 17KV (Vpeak = 1.414*Vrms). A two bushing NSTs would have 6KVrms (wrt ground) on each bushing (12KVrms between the two bushings) . Don't know how you are measuring your voltage, but a ruler isn't the way to go. Set each side of your safety gap with no load attached to the NST. Then you can reconnect the TC primary.
If you use the mains ground for an RF  ground, do not allow the 
coil arcs to hit anything (walls, ceiling, etc) not directly 
grounded to the TC secondary base.  Use an outlet on a circuit 
breaker branch that is not shared with anything else and use a 
counterpoise.  Also unplug anything electronic (TV's, computers, etc)
Best to go outdoors and ground your TC secondary base and strike 
rail (if you have one)  to RF ground (rod driven into the earth with wet soil).
If the NST is located with your TC (like just under the TC 
primary),  I would ground it (along with its protection circuit) 
to RF ground and NOT to mains ground.  If you use a line filter, 
it should be grounded to mains ground. Your variac should also be 
grounded to mains ground.


Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>

TWO THINGS:
1.) I know this is "very, very bad" but i use mains ground for my entire circuit 2.) that being said, i have my NST, safety gap, and secondary all linked to the same exact ground
*what do you mean unloaded NST? You want me to basically 
disconnect the ENTIRE tesla circuit, after my safetygap? If i do 
so, the safety gap will fire, up to aobut 15KV.
15KV is still enough to damage my transformer's(12,000/30 ma) 
secondary isnt it? So, my safety gap would be useless set at 
such a huge voltage. I think it should be set at about 1KV over 
what my NST is set at. (my NST is set at 7,500 volts with my 
spark gap, so the safety gap should be 8,500 to 9000 volts)

NO ONE HAS ANSWERED MY QUESTION YET THOUGH:
CAN MY EARTHED MIDDLE NODE ON MY SAFETY GAP BY REPELLING A SAFETY SPARK?
Not sure what your question means.

Gerry R.