Re: Safety FAQ is here -- draft, asking for comments.
Malcolm Watts wrote:
> Hi Robert, all,
> I'm afraid I can't agree with your hypothesis....
> > I believe that the phenomenon which is being bandied about where some
> > people believe that the discharge channel is growing on itself is
> > completely illusory and false.
> The problem is when you consider the phenomenon using (a) synchronous
> breaks, and (b) using static gaps. My large coil with its current
> (npi) gap setting produces a streamer about 11" long when operated
> single shot, 4ft+ when repetitive. Greg Leyh had some info on this
> that you may have seen (although he was using async rotary).
I would like to offer two observations that tend to support the
'arc growing on itself' theory:
A: In Uman's famous book 'Lightning' (Dover Books, 1969), there are many
nifty streak camera photos that show natural lightning actually propagating downwards,
in small segments called 'stepped leaders'. According to the author, each successive
stepped leader adds 10 to 200 meters to the propagating end of the arc, at
repetition rates of 100 Hz to 20kHz. The rep rate is determined by the capacitance
of the cloud, which acts somewhat like a relaxation oscillator.
B: I have noticed that the spark length from the toroid is a strong function
of rotary gap speed, where the output arcs at full speed (300pps) are almost
twenty times longer than at those at tuning speed (1pps).
And although the gap isn't synchronous, there's nothing for it to be
synchronous with, as the power supply for the primary is DC in this case.
It is possible for the gap firing rate to beat with the ripple on the DC supply,
but the ripple is not be larger than 14% of the supply voltage, since it's derived
from full-wave rectified 3-phase. The ripple would have to be around 95% for the
beat frequencies to account for the 20 to 1 growth in the arc length.