Re: how much does current matter?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>


Current does matter a lot.  It allows you to use a larger capacitor 
which in turn allows a large topload which produces longer sparks --- 
not necessarily higher voltage, but longer "plasmas" and hence longer 
sparks.  Everything is "interconnected" in TC design.

The usual equation is the Feau equation, which states:

D = 1.7 x SQR P

where d= spark length in inches and p is power in watts

In actual practice, with a 30 or 60 mA NST I usually use D = 1.3 
x  SQR P for initial designs.  1.7 value is achieveable but requires 
near perfection in all aspects of design.

You need the neon xmfr to produce the high voltage to make the 
sparkgap fire which acts as a high speed switch.  The exception to 
the rule is the solid state coils which use IGBTs with higher 
currents and lower voltages.  The faster the switch rate of current 
through a coil the higher the output potential in accordance with the 
laws of physics:

V  =  -L x dI/dt

V = potential (voltage)

L = inductance of coil (the minus sign indicates reverse polarity 
with respect to the primary coil, ie, Lenz's Law (physics again)

dI/dt is basic calculus which indicates the rate change of current 
(I) with respect to time (t) in seconds.  I is measured in Amperes 
(from physics for Intensity).

The quick dI/dT is what allows solid state coils produce large 
outputs with low voltage as they use higher average peak currents 
(greater I value) very rapidly switched on and off.  Solid state 
coils are very compact, neat, and operate at least 30% more 
efficiently than open air spark gaps which waste a lot of energy in 
the forms of heat and light.

Dr. Resonance



From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, March 04, 2006 2:09 PM
Subject: how much does current matter?


> Original poster: ben eells <squeels2171@xxxxxxxxx>
>
> In my attempt to build a more powerful tesla coil I have come across 
> this question. How much will the output current of your NST affect 
> the length of your streamers. I'm using the program Tesla map to 
> help design this coil and it calculates the max streamer length by 
> the output wattage of the NST. Unless I'm mistaken output wattage 
> can never be higher than input wattage. If this program is correct, 
> and I'm sure it's not, I wouldn't need a transformer at all. So what 
> is a better way to determine max streamer length given the output 
> voltage and current of a NST?