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Re: Arc length vs pwr
Hi all, I have been lurking here for some time time now and I have found
the discussion fascinating. The posts about arc length vs power peaked my
interest, so here's my two cents.
I found (in several volumes) Charles Steinmetz's lectures at the local
used bookstore. In volume I, he gives the power consumed by an arc as
p = c * l * sqrt(i)
(c is an empirical constant, l is length, i is current)
The reasoning is that the current is proportional to the cross-section of
the arc, while losses due to convection, radiation, etc. are proportional
to the surface area of the arc.
using the formula
input power = v^2 * 2 * PI * 60 * c
and some rearranging, the formula is now
l = (a * p^.75) / sqrt(Cs)
p = power, Cs is capacitance (pf)
IF YOU ASSUME CONSTANT CAPACITANCE, the formula matches with an R of
.99980250 with the data posted by Jack Couture
POWER INCHES CALC'd
500 11 11.55
1000 20 19.43
2000 32 32.68
5000 64 64.97
10000 110 109.26
using .10926411 for (a/sqrt(Cs))
In light of this I am wondering whether Couture's data was from
a single coil or coils which were run at various power levels -- instead
of many different coils at many different power levels.
Factoring in the capacitance means that coils with small secondary
capacitance would have a somewhat bigger arc length at the same power.
Just my two cents, feel free to disagree, standard disclaimers,
Chris Bailey - cbailey-at-ideanet.doe.state.in.us