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Re: Homebrew HV transformer help



> Original Poster: "Jon Lagler" <rockcrawl-at-netzero-dot-net>
> 
> I'm working on rewinding a transformer for TC use. The core is from an old
> welder and has a variable current shunt, or at least I think it's a current
> shunt. If I'm correct, this will work like the shunts in an NST, and no other
> current limiting will be needed...

>...My question is how to configure the secondary. Do I need
> a center tapped secondary? Because of the moveable shunt laminations,
there is
> only room for two coils, unlike a neon which has three.

You can not center-tap a single coil secondary.  It would not serve any real
purpose, but would give you a big insulation obstacle.  Specifically,
bringing the center-tap wire to the outside would be impossible since you're
talking about more volts than the enamel can fend off (unlike in a
120-to-12.6VCT, where it's safe).

Neons are center tapped for safety reasons only, so that if someone comes
into contact with a bushing they only get half of the maximum voltage,
increasing their chances of survival.
 
> 2. Primary wound on one bobbin, secondary wound on separate bobbin with CT at
> 1/2 of total turns.

Would not work, for the reason described above.

> 3.Split primary between two bobbins, split secondary wound on top of
> primaries, with CT obviously between the two separate coils.

Nope, now you've got effectively no shunting, since the primaries and
secondaries are on the same leg of core.
 
-Adam
adamsmith-at-mediaone-dot-net