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Re: Common ground for primary circuit
Hi David,
Pole transformers are generally 240VAC output. We reverse that and put 240 in.
This is applied across the full winding. Each leg is hot. Each hot to ground is
120VAC. We could use ground and one leg, but then we wouldn't get the full use
out of the transformer. My pig has three low voltage fasteners. The center
fastener is center tapped and the outer two fasteners attach at the winding
ends. I put the 240V across the two outer fasteners leaving the center tap as
is. Lp to Ls is 60:1,so 240v in is 14.4KV out. I ground the casing to house
ground as there is a fastener for that at the bottom of the pig. It is
important to use dual-trip breakers, external ballast, and a voltage control
variac on pigs (and amp/volt meters).
If the power company would supply 240V on one leg as measured to ground, I
would be just as happy to use that, but they don't and it's not necessary -
it's still a loop of voltage/current with a Tesla circuit in the middle, just
like 120V, except earth ground isn't attached to one of the mains.
Bart
Tesla List wrote:
>
> Original Poster: Tesla729-at-cs-dot-com
>
> Hey all,
>
> I was wondering why a lot of coilers insist on not grounding one of
> their HV xfmr's two output leads as a common grd. and letting the
> other lead be the "hot" lead? I of course realize that this is not an
> option for most NSTs as they are almost always sec. midpoint
> grounded or for some ganged xfmr arrangements, but for a single or
> double HV bushing pole pig, why insist on two "hot" leads and a
> grd. instead of only one "hot" lead and a com. RF grd?
>
> David