Re: Output of Neon Sign Transformers (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 18 Jun 2007 08:03:55 -0700 (PDT)
From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Output of Neon Sign Transformers (fwd)

4kV or 8kV, your MMC voltage rating is still almost
certainly too low.  Even with the very best MMC caps
(the CDE 942C series), your DC voltage rating should
never be less that the peak voltage of your
transformer.  In your case, that would be *at least*
4kV * sqrt(2) = ~5.6kV.  So you are already pushing
things.  Many people apply a 2 x Vpeak rule when
building MMCs, and would use at least twice as many
caps in a string as you are.  Of course, if your
transformer is 8kV, then... :-)

As for whether the NST is 4kV or 8kV, the "4000V - E -
4000V" thing sure makes it sound like 8kV.  Are there
two high-voltage ceramic bushings, or only one?  Hard
to say from the drawings in the documentation. 
Normally, for a NST of only 4kV, I'd expect that one
of the HV terminals would be grounded to the case. 
Checking for that with a DMM ought to be really easy. 
Alternatively, you can see if arcs are longer
bushing-to-bushing than bushing to case.  If so, then
it's almost certainly 8kV and not 4.

Regards,
Aaron, N7OE

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> 
> ---------- Forwarded message ----------
> Date: Mon, 18 Jun 2007 11:27:14 +0000
> From: Nicolas Alstrup <n_alstrup@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: Output of Neon Sign Transformers
> 
> Hello,
> 
> I have found two identical neon sign transformers,
> that I am trying to build 
> a Tesla Coil Around, but I am experiencing some
> difficulties..... My main 
> problem is that I can't figure out my transformer
> output, and my MMC 
> capacitors keeps blowing.....
> 
> The Transformers are from Neoncomp, www.neoncomp.fi,
> type "N 50/8 RE" and 
> here is what it says on them regarding the
> secondary:
> 
> Us = 4000V - E - 4000V
> Is = 50 mA
> Pp = 520VA
> 
> On the homepage it is described as a 2x4000V
> transformer, but does that 
> means it gives out 8000V?
> 
> I have parallel connected them, and beleive that
> should give a output of 
> 4000V and 100mA. Right?
> I have used 40 x 0.047uF 1000V capacitors, 5 in
> string, 8 strings 
> parralell.. This should give me 0,0752uF, and 5000V
> potential, but the 
> capacitors keep blowing... Any Ideas, thoughts
> regarding the transformers?
> 
> Thank you very much, sincerely Gryphon
> 
>
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