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Re: Ground strike currents and time...



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 08:01 PM 6/3/2006, you wrote:
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

So I made the fastest Inductive current loop I could with the parts I had:

http://drsstc.com/~sisg/files/scantesla/DanQ-07.JPG

It's just a loop of wire and a low inductance 50 ohm resistor on a 50 ohm BNC cable. The other end of the cable is also terminated into 50 ohms. This is the signal:

http://drsstc.com/~sisg/files/scantesla/DanQ-08.gif

40V at 10nS rise times!!! That is the limit of the scope now!!! And the real signal is obviously "faster still"...

And that might actually be more the ringing in the wire and/or transmisson line than the actual current waveform. How long is the wire?




That puts the current pulse in the range of 10 - 20 nS and the current in the 1000 to 2000 amp range!! For a 108kV 3.7 inch spark off a 31.1pF toroid!!! Goodness only knows what a 5 foot streamer to ground is =:O The streamer resistance is roughly 100 ohms in that case.

The peak power for a few nS is over 100,000,000 watts!!!! For just a "little" spark...

Cheers,

        Terry