Re: Home Made Variac

• To: tesla-at-pupman-dot-com
• Subject: Re: Home Made Variac
• From: "J. B. Weazle McCreath" <weazle-at-hurontel.on.ca> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Fri, 04 Feb 2000 06:35:06 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

At 04:22 PM 03/02/00 -0700, you wrote:
>Original Poster: "Michael Novak" <Acmnovak-at-execpc-dot-com> 
>
> 
>     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?
> -Michael

Hello Michael:

I think you'd have a pretty hard time home brewing a variac if for no
other reason that finding the circular core material.  However, there
is another approach you might take.  You could wind a conventional
auto-transformer with many taps to provide you with a stepped range
of outputs as opposed to the smooth afforded by a variac.

Assuming you'd run it on 120 volts, an autotransformer with taps at
10 volt intervals from 60 volts up to the full 120 would give you a
pretty good range of powers to choose from.  Hunt around for a good
sized core, with a cross sectional area in the range of about 8 to
10 square inches, and wind it with 2 turns per volt of number 12
formvar wire.  I've a similar unit that I made for my resistance
soldering machine, and it has worked well for many years.



73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
           or ve3ear-at-rac.ca
Web site:  www.hurontel.on.ca/~weazle

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