arc voltage drops

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

I just ran across an equation that may be useful for those of you
simulating spark gap losses.

It comes from Khalifa, High Voltage Engineering, page 153

Steadystate DC arc voltage
V = a + b*length + (c + d*length)/current

where typical constants for air, up to 5 cm length, and arc currents up to 20A

a = 17V
b = 22V/cm
c = 20Watt
d = 180W/cm

For a general energy balance standpoint... E = C*I^(-1/3)

The following pages discuss some issues about AC arcs.. having to do with
temperature of the arc column (i.e. the resistance) lagging the voltage.

They cite Cassie and Mayr (separately) to come up with an "arc resistance
after current zero" relation of the form:

R d/dt 1/R = 1/theta *[ (VI/W)-1)

There is some discussion about "quenching" in the sense that you can
determine from an energy balance whether the arc will reignite after a
current zero.