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Re: Controling a Pole Pig

Tesla List wrote:

> Steve
>  >     I do have a related question though, I have 2 pigs, and was wondering
>  if I
>  > could use one of them as a variable inductor by putting a variable gap in
>  the
>  > core and then putting the 240V side of both pigs in parallel, not
> connecting
>  > anything to the 11 kV side of the gapped pig. Does anyone have any
>  > experience of
>  > this, will it work?
>  >
>
> Jim Lux wrote:
>  YEs something like this will work... This is how inexpensive welders set
>  the current. They have a core with lots of extra room in the middle
>  (where the windings are. Then, they have a piece of core (the shunt)
>  which slides in and out, changing the leakage inductance, as you turn
>  the handle (which operates a lead screw or other mechanism). When the
>  shunting core is all the way out it is max current, all the way in is
>  minimum.

    This does not appear to be quite what I meant, What I had planned was
to use a
transformer as a limiter, so I would NOT be connecting the 11 kV winding at
all -
in effect it does not exist. In any case due to the way the transformer is
constructed, it is not possible to place a shunt in the core which would
cause an
increase in leakage inductance. Because the windings are wound over one
another,
any flux which passes through one coil must also pass through the other, so
there
can be no significant leakage inductance when they are operating as a
transformer.
I was proposing to only connect the 240V winding and use the transformer as an
inductor, with a variable inductance caused by a variable air gap in the
magnetic
path.

      240V winding
-----           ------------------ || -----------
    |           |                | || |
M    ~~~~~~~~~~~                 ~ || ~
a    ----  -----             240V~ || ~           Coil (11 kV)
i    ----  -----                 ~ || ~
n    Variable gap                ~ || ~
s                                | || |
---------------------------------- || -----------
    Transformer 1            Transformer 2

Transformer 1 is being used solely as a variable current limiter and has a
variable air gap in the core, and transformer 2 as the actual output
transformer
and is unmodified. Sorry if I didn't make this clear in my initial posting.
Does
anyone have an experience using this arrangement?

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