Arc welder source (fwd)

From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
Sent:  Wednesday, April 01, 1998 10:30 AM
To:  Tesla List
Subject:  Re: Arc welder source (fwd)

In your frenzy of arc welder searching and buying, I should warn you that
the latest trend is to go from classical series inductive current limiting
to (gasp) solid state switching power supplies. Even in days gone by,
ignitrons and then SCR's have been used to regulate the current output on
large welders (pretty soon, the inductor just gets too big) ( I remember an
example of this from an EE textbook in the late 60's).

And now, modern technology allows you to make a small lightweight welder
without the weight penalty of a big inductor for current limiting.

If you've ever taken apart a small "buzz box" welder, you see that the knob
that sets the current just adjusts the position of a sliding magnetic shunt
in the transformer, which changes the leakage reactance of the transformer
(just like a NST).  Simple, effective, cheap to manufacture, but, pretty
bulky and heavy.