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Re: Doubling NST voltage? (fwd)



Original poster: "Mike" <mike.marcum@xxxxxxxxxxxx>

Another option would be to take the 6/20 open-core (no tar to deal with) nsts and series 3 (best if the center one is a midpoint grounded version) and submerge at least the outer 2 in oil (all 3 if no midpoint ground). These types have considerable space between the core and windings so the oil helps quite a bit.

Mike
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, October 30, 2006 2:04 PM
Subject: 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)