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Re: Doubling NST voltage? (fwd)



Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Mon, 30 Oct 2006 10:00:45 -0800
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Doubling NST voltage? (fwd)

At 06:45 AM 10/30/2006, you wrote:
>Original poster: List moderator <mod1@xxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Sun, 29 Oct 2006 11:37:22 -0800 (PST)
>From: C. Sibley <a37chevy@xxxxxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: Re: Doubling NST voltage? (fwd)
>
>I still don't get it, why would you need an isolation transformer for the
>second transformer?  It seems to me there would be no problem as long as
>the CT of the secondaries were left isolated (i.e. floating).
>
>Is the concern there would be a breakdown between the seconday to primary
>within a transformer?

Precisely.  The reason the centertap is grounded in a NST is that it 
makes it possible to insulate for only half the total output voltage. 
That is, a 15 kV RMS (21kV pk) transformer would only need 11kV insulation.

NSTs are a hugely cost sensitive device, and they don't spend a penny 
more on insulation than they absolutely need to.

They do breakdown if hooked up in series.  Typically, since the 
secondary is connected to the core (at the midpoint), the breakdown 
is core to primary (at least in my transformers I've tried this with)