Re: 20 joules at 100 bps vs 4 joules at 500 bps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: boris petkovic <petkovic7@xxxxxxxxx>

Hi Malcolm,
-----
>  >
>  > "Model 10 Tesla Coil used to trigger man-made
> lightning across six
>  > foot gap. This discharge is over 10KA at less
> than 5 usecs. rise time,
>  > producing a large electromagnetic pulse (emp).
> Storage capacitor used
>  > is rated at 60 KVDC, 75 Joules."
>  >
>  > "less than 5 usecs. rise time" - oh yeah? and
> what secondary
>  > inductance do we need for this? did they ever try
> to calculate?
>  > impossible! LOL :-)))
>
> Maybe not. Consider that at the point of spark
> initiation the
> terminal is at some high voltage - for a brief
> interval it could be
> considered to be HVDC. Spark propagation is a pretty
> rapid event by
> comparison with the resonant frequency. I think you
> can discount the
> impedance of the secondary when considering such an
> event.
>
> Malcolm
>
-----
IMO,Dmitry has got the point there ,if he refers to
way how the bulk of the energy in the storage
capacitor should be dissipated.At least,my impression
is he rises the following point:
When *streamer* propagating from TC secondary contacts
the terminal of the capacitor, a new circuit is
formed.
That circuit has a characteristic impedance

Z=SQRT(L/C)

where
L...low frequency  inductance of the resonator
C... capacity of the storage capacitor

For C~4uF (if that was the cap value) and M10 coil
inductivity range ,it turns out Z=50...100 ohms.

With V~60 kV ,a slow rising current amplitude would
"only" have a peak 500-1200 A.
And It takes several hundred microseconds to reach
that magnitude!
Of course,there are finite conductances of the
secondary wire and arc included in the path (meaning
that true circuit is of RLC type.So the transient may
be heavily damped or an aperiodic one - more like
natural lightning) .
However it is not 10 kA nor 5 microseconds.I guess it
was offhand estimate by Bill W.

I imagine high inital currents (like several
kiloampers) were present in transition times ,in the
begining of forming of the new circuit  having high
frequency superimposed noise.Spurius L-C ,and
distributed networks are the cause.
Nevertheless, such large spikes also occur in the
begining of a firing cycle in a primary gap and ,as
known,carry away only a small percentage of the
primary cap stored energy.

One way or another,500-1000 A is not a small current
on arc scale,and is comparable by a TC primary gap
current (and lasts longer).Must had been a hell of
discharge back in 1981'.

Best Regards,
Boris

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