Re: Spark-Gap Voltages

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Bart,

        I like to have rotary gaps set "really close".  As close as I can
safely
get them.  This seems to cut down on gap loss a bit.  But the best reason is
that you have a wide range of power control with the variac.  When the voltage
is still pretty low, the gap will still fire allowing the coil to run at lower
levels.  Also, LTR coils need to fire the gap 'before' they will go to full
power.  So a tight gap setting helps get them started.

Rotary gaps tend to fire before the electrodes actually align.  I think the
high air flow and such make them need high voltages to fire than if they were
still with the same gap.  I have not actually proven this but working with
them, they seem to behave that way.

Cheers,

        Terry


At 01:26 PM 7/29/00 -0500, you wrote: 
>
> Hi Terry, All, 
>
> Terry, thanks for posting the Spark-Gap Voltages. I copied this quite a while
> back, but you reminded me of the Spark-Gap table. 
>
> Assuming Vp of 20kv at the gap is a typical voltage for us. According to the
> table, for a 2.5cm sphere (~ 1 inch) the gap voltage is .58cm (~.23 inch). A
> needle point at 20kV is 1.75cm (~.69 inch). This table seems to reflect
> static gaps well, but does a rotary gap apply? 
>
> I typically run a .008 inch gap (total). Since a rotary gap is aligned only
> during specified breaks (bps), it shouldn't matter what the gap spacing is,
> as long as it is set close enough to arc and far enough apart to not come in
> contact electrodes. It appears to me that changing the gap will only set when
> it fires as the electrodes align. 
>
> Does anyone disagree with this? (or agree), 
>
> Thanks, 
> Bart