Re: Putting two potential transformers in series

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FutureT-at-aol-dot-com 

In a message dated 12/19/03 10:02:44 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

> >   Hi all,
> >
> >   I have access to a couple 7.2 KV potential transformers and was
> >wondering if I could wire their secondaries in series to get 14.4 KV,
>which
> >seems to be a more desirable voltage to use for coiling. I know this isn't
> >a good idea for neon transformers, but since potential transformers have a
> >Basic Impulse Level (BIL) rating of around 100 KV, would there still be
>the
> >possibility of flashover internally like with NSTs? I realize the I in BIL
> >stands for impulse, but at 7.2 KV maybe there's sufficient internal
> >insulation to wire them in series without the flashover risk. Anyone have
> >any experience in this area?
> >
> >
> >Thanks in advance,
> >
> >Rick
> >
> >
>


Rick,

Yes, you can run the transformers in series.  Actually even if it
didn't have such a high BIL rating you could do it safely.  This is
because a PT is not a center tapped transformer, thus by putting
two of them in series, you're in essence creating a center tapped
tranformer of sorts.  A NST is already a center-tapped transformer,
so this is why they can't be put in series.  However there are some
lower voltage NSTs that are not center-tapped, and they can
safely be connected in series.  MOTs can also be wired in series,
and this is often done to obtain a higher voltage.  MOT's are not
center-tapped.

John