Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 16 Sep 1997 16:05:57 -0500
Approved: tesla-at-stic-dot-net

From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: 	Tuesday, September 16, 1997 5:02 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark

In a message dated 97-09-16 01:29:28 EDT, you write:

<< 
> I am just starting to get good results with my 6" 15Kv 60MA setup. The tank
> capacitor is 14 nF (for 50Hz) rolled poly (two series 28 nF caps). The best
> I have done so far is 35". I am using a tripple gap system quenched with a
> microwave oven fan. What I have found is that to get the long sparks the
> gap must be made quite wide to take advantage of the resonant charging.

Jason,

Yes, a wide gap is essential for these very long sparks.  I ran a TC for 
awhile using widely spaced static gaps, but not long enough to judge
how long the transformer would survive.  I then went to the sync-gap
as part of ongoing experimentation on quenching.  But numerous
people on the list have expressed concerns that wide gap spacings
will kill the tranny.  No doubt a safety gap of some sort is essential.
I think I had my safety gaps around 10mm, maybe a little more, when
I used 15kV, 60 ma, and obtained 64" sparks using the sync-gap.

> When I got to about 12MM (1/2") the terminals from my two 15Kv 30 MA
> tranies started to arc to the case which is about 10MM from the edge of the
> HV insulator. I supose this is a good saftey gap and may well have saved my
> transformers.

Yes.

> My question is how far should I open the gap to take advantage of resonant
> charging ? he gap has never miss fired yet. It apears to me that I should
> set the gap to fire around the 30 KV mark. I'm not game to do this because
> my caps were not designed with this voltage in mind , but in the future
> they will be.

I agree that to get the long sparks, you would have to aim for around 
30kV, once you get suitable caps.  In an earlier experiment, I obtained
46" or so from a 15kV, 60ma, with four static gaps set at about 1/8" 
each, for about 1/2" total.  But I suspect that the quenching was
marginal, no air was used.  

The use of a large enough toroid is essential also...I use a 6.5" by 26"
unit.  If you're getting more than one streamer at a time, this will
reduce the spark length.  Longest sparks will occur when only one
streamer forms.  This can be controlled by adjusting toroid size and
coupling.  Looser coupling sometimes gives longer sparks in these
systems.

Since you're using 50Hz, the air has more time to de-ionize between
bangs, but I don't know if this makes much difference.

John Freau

> Cheers,

> Jason
  >>