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Re: Home Made Variac
Velcome to the club.
The standard variac is an auto transformet, where the tapping point is
at the roller or dragging carbon shoe or whatever. The full mains
voltage is normally connected at the ends of the winding. However it is
quite possible to make a variac that steps up, by attaching the mains to
a tapping point at somewhere in the middle.
Only thing that you need to insure, is that you have enough windings on
the core to avoid that the core saturates. Cores that are 2"/2.5"
(50mm/65mm) normally wind up working well with 1 turn per volt.
If you get a suitably sized toroid transformer, which would be one that
can sustain the power level you plan to operate at, strip the
secondaries off, then count the turns on the primary. They will reveal
the amount of turns you need for the variac, provided that it is made
for the mains potential that you use.
Mine was made to be usable from 220V(single phase), 380V (btwn 2
phases), and furthermore stepping up to a maximum of 480 V in both
modes.
You can see my own handwound variac here:
http://home5.inet.tele.dk/f-hammer/tesla/tesla.htm
Cheers, Finn Hammer
Tesla List 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