RE: Home Made Variac

• To: tesla-at-pupman-dot-com
• Subject: RE: Home Made Variac
• From: Eric Leighton <ELeighton-at-portdiscovery-dot-org> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Fri, 04 Feb 2000 13:50:30 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Michael wrote: "I can't afford to buy a variac but I need some way to vary
the line voltage... So, I decided to build one. I'm pretty sure I can get my
hands on some 10 guage magnet wire, however, I still need to find a suitable
core. Isn't a variac basically a bifliar-wound 1:1 turns ratio transformer?
If so, does anyone have some sort of formulas on the subject?  What would be
the
disadvantages of having a core which is not laminated such as the kind found
in transformers?  Any thoughts?"

I would think it would be easier to find a "dead" variac (typically the
brush goes bad) and fix it up (search the archive on brush and variac).
There are lots of people with more money than time who'd likely let theirs
go.  If you can loosen up the corrosion holding the old brush, you can
custom fit a new piece of carbon.  The job becomes more difficult if
removing the remains of the old brush destroys the whole brush unit, and not
just the carbon.  I have two variacs in the latter category, in a box under
a bench in my shop, one an old Variac 5V, and the other a Powerstat 116.
I'd be happy for any suggestions regarding fixes for these.  BTW, the Variac
brush holder is a 3/8" whole, and the Powerstat's is a 3/8" square.  Anyone
know a good alternative?

Eric Forsman
Baltimore, MD

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