[TCML] Spark gaps (again)
jimlux at earthlink.net
Mon Mar 9 20:37:06 MST 2009
Dex Dexter wrote:
> I'm not so sure about thin that much final diameters for a Tesla gap spark.
> Read here (section 3.2) about diameter of steady state and low frequency arc:
> I took in my estimate 1000 A primary current arc to expand to about d=10 mm.
> 100 A current is probably closer to low powered coil,but it depends also
> on operating frequency.
> What is radial average velocity of expanding column of such arcs it's hard to tell.
> I don't have data and I'm interested to learn.
The diameter data they give is 3cm at 7.8kA. Also a cathode spot
current density of 2.4kA/cm2. At a primary current of 100A, that energy
density works out to .04 cm2, a radius of about 1mm
If you consider a typical medium sized coil with 130 uH and 0.01 uF
primary charged with 15kV, the current is about 130A. (based on LI^2=CV^2)
I'll have to track down the paper by Latham, since it apparently talks
about lightning, which is a fast transient, probably more representative
of what's going on in a TC primary gap.
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