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Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark
From: Jason Judd[SMTP:Jason.Judd-at-anu.edu.au]
Sent: Monday, September 15, 1997 7:43 PM
To: Tesla List
Subject: Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark
> << John, Malcolm & all,
>
> > Nice experiment, John! Even though you're firing synchronously every
> > half cycle, you're still seeing the impact of resonant rise. This
> > experimentally confirms an earlier question regarding whether you'd get
> > resonant rise if you synchronously fired on each AC half-cycle.
>
> Bert,
>
> Thanks. Do you mean resonant rise in the charging circuit,
> it seems to me that 120BPS sync operation would be better
> for resonant rise in the charging circuit than a higher break-rate
> would be, since there's more time available for the resonant rise to
> occur.
>
> > Under these conditions, Glasoe ("Pulse Generators") predicts voltage
> > rise of Pi/2 times input voltage. Peak input voltage is about 20.4 kV
> > from your potential transformer, leading to a predicted peak of 31.2 kV
> > versus 32 kV measured - pretty close agreement! If you "missfire" just
> > once, or only fire synchronously 1/cycle, the predicted value climbs to
> > Pi*20.4 or about 64 kV (:^()! And it potentially (NPI) gets much worse
> > with asynchronous firing!
>
> Ho! I agree, ain't it great!
>
> > While your potential transformer will shrug off this transient, a neon
> > would probably be toast! This definately confirms the moral of not
> > running a neon with an async gap, especially if close to 60 Hz
> > resonance. However, it also speaks to the issue of conservatively
rating
> > your tank cap!!
>
> Very true. My cap is rated at 90kV. Sometimes, when my gap
> electrodes wear, I may miss some firings before I re-adjust the gap,
> of course, the safety gaps should fire.
>
> John Freau
>
> > -- Bert --
> >>
>
>
Hi all,
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.
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.
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.
Cheers,
Jason