Re: What it all does..

["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>


> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> Hi Pjj,
>
> Of course, most small coils do run off 120VAC :-)  However, I assume you
> mean why one can't run the primary coil from say 100 volts instead of many
> thousands of volts.
>
> Tube and other CW coils do run with only a few hundred volts on the
> primary.  However, all big disruptive type coils tend to use very high
> firing voltages at around 20kV.  The high voltage is needed to force a lot
> of current through the inductance of the primary coil.

>
> Higher voltages also help the spark gap to work.  However, solid state
> elctronics has sort of removed that as a problem.

In fact, voltages less than 350V (give or take a bit) can't spark over a gap
(of any length) in air at normal pressures/temperatures. You can "draw" an
arc at lower voltages (i.e. start from touching and pull apart, like in arc
welding), or trigger one with a higher voltage pulse (as used in TIG welders
(GTAW) or plasma cutting), but you won't ever spark over.  It has to do with
the breakdown characteristics of gases.