RE: Spark Gap Firing?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>


> Original poster: "Tom Heiber" <tom.heiber@xxxxxxxxx>
>
> When gapping the distance between electrodes. Should the spark gap
> fire without the Tank Cap conected?

Yes, but only at maximum Variac, if you're using one.


> How do you determine the optimum gap distance?

With only the NST hooked to the gap (i.e. no cap), adjust the gap width
so it just barely fires at maximum Variac.


>  From what I understand, the gap fires when the capacitor is charged
> with enough energy to ignite the spark.
> That would indicate that the gap should be set so that without the
> cap, there would not be sufficient energy to fire up the spark, but it
> should fire with the cap connected?

Technically, the gap will fire when the capacitor (and gap) _voltage_
(not energy) is sufficient to fire the gap.  You want to set the gap
width so that it fires at the maximum voltage that the NST was designed
to withstand, or the peak NST secondary voltage.  For a 15kV NST, this
would be about 21kV.  What's not obvious is that if the gap is set wider
than the peak secondary voltage, depending on the value of the
capacitor, this higher than NST-rated voltage can easily be developed,
through mains resonant rise.  Performance will increase with wider gaps,
at the cost of increased peril to the NST.

Regards, Gary Lau
MA, USA