# Re: Residual Cap Voltage

```HI.

>From my measurements, residual voltage was from 0 to 100 V, practically nearly
always 0.

Regards

Tesla List <tesla-at-pupman-dot-com> on 01.01.2000 23:03:48

To:   tesla-at-pupman-dot-com
cc:    (bcc: Marco Denicolai/MARTIS)
Subject:  Residual Cap Voltage

Original Poster: "Steve Young" <youngs-at-konnections-dot-com>

Hi folks,

The following is a question for those who can base their answers on actual
measurements (scope traces, etc.):

I am interested in knowing what the approximate typical residual voltage is
immediately after a "bang" of the spark gap.  Assume the TC has operated for a
half a minute or so to achieve typical spark gap conditions (temperature, ions,
etc.).

I visualize if the cap charges up to V volts, then right after a bang (gap not
conducting until the next bang) it will be less than a tenth V, since the gap
is quite a low impedance while it is conducting.

This information should be useful for determining the peak current one can
expect in the cap, which could be useful in designing MMCs.  If the cap
discharges to near zero volts, then the peak current will be about V/Z for each
bang, where Z is the impedance seen by the cap during the start of each bang.
But if the residual cap voltage ends up at, say, half V, than the peak current
could be up to 1.5V/Z on the next half-cycle of the AC charging.

Thanks in advance for comments, and welcome to another great (and safe!) year
of coiling!

--Steve Young

```