Re: 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>

Yep... The text makes it real clear that this is for steady state DC!.(and
for currents substantially lower than the peak RF current).. And goes on to
discuss all the ramifications of AC.. Most of the discussion is centered
around 50-60 Hz, where the period is quite long compared to the time scale
for thermal changes/diffusion in the gap.  I was thinking that as a first
cut, you could assume that the process is quasi stationary over the time
scale of a "bang", and just numerically integrate a damped sinusoid (I'll
leave it to better mathematicians than me to do this analytically).  I'm
looking around for some data on the thermal time constants involved, which
would be very useful..

However, this does give a starting point...

There is probably some good empirical data around from the days of "King
Spark".. It just needs to be tracked down.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, April 09, 2002 6:57 PM
Subject: Re: arc voltage drops


> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
>
> Hi Jim, all,
>              One must remember that in a TC, the current used in the
> is a (sinusoidal) function of time, not a DC value and will give
> other than a steady resistance when plugged into the equations.
>
> Regards,
> malcolm
>
>
> On 9 Apr 2002, at 1:24, Tesla list wrote:
>
> > Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <scepp-at-mts-dot-net>
> >
> > Can you elaborate on these equations.
> >
> > The values that you use, are these an example?
> >
> > Shaun Epp
> >
> >
> > ----- Original Message -----
> > From: "Tesla list" <tesla-at-pupman-dot-com>
> > To: <tesla-at-pupman-dot-com>
> > Sent: Monday, April 08, 2002 7:17 PM
> > Subject: arc voltage drops
> >
> >
> > > 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.
> > >
> >
> >
> >
> >
>
>
>
>