[TCML] Another NST question

[Neal Namowicz]

I've already gone the parallelling route, but one still winds up with 9kv at 
60ma. My 15/60 easily outdoes that by itself. I was looking for the extra 
voltage, but I forgot about the center-tap. Oh well, thanks,

Neal.


----- Original Message ----- 
From: "Lau, Gary" <Gary.Lau at hp.com>
To: "'Tesla Coil Mailing List'" <tesla at pupman.com>
Sent: Friday, December 07, 2007 3:39 PM
Subject: RE: [TCML] Another NST question


The reason that you CAN'T series NST's is that for NST voltages at and above 
something like 6kV, the secondary winding are constructed with their 
mid-points connected to the NST core and case.  So for a 9kV NST, one hot 
lead is at +4.5kV relative to the case, the other at -4.5kV relative to the 
case.  If you tied two 9kV secondaries in series, there would be 9kV between 
their cases.  On the surface this doesn't sound like an insurmountable 
problem until you realize that the primary windings are not built to 
insulate many kV to the core.  Since the primary windings are tied together, 
there are two core-to-primary insulation barriers between the two cores that 
are 9kV apart.  It's not built to withstand that much and will break down.

You can deliver just as much total power to the coil if you just parallel 
the secondary windings.  No problem with that at all.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of Neal Namowicz
> Sent: Friday, December 07, 2007 7:28 PM
> To: Tesla Coil Mailing List
> Subject: [TCML] Another NST question
>
> I thought I had read before that nst's shouldn't (couldn't?) be put in
> series to double their voltage, that it would be too much of a strain on 
> the
> secondaries. But, we all know that there's some "wiggle room" in their
> construction, otherwise we couldn't get away with removing shunts and
> doubling the ma output. So assuming that one phases them correctly, is it
> possible to series two of them together? I was thinking 2 9kv/30ma's to 
> give
> me about 18kv, slightly less if I don't drive it to 100%. I just chose 
> that
> size because I have them already. Thanks everyone for your input on this.
>
> Neal.
>
>
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