Re: Variac rebuild

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jan Wagner <jwagner@xxxxxxxxx>


On Wed, 2 Feb 2005, Tesla list wrote:
> Original poster: Blake Hartley <teslaspud@xxxxxxxxx>
> Maybe you remember, but a while ago my four amp variac brokedown due
> to several burned and broken turns. Seeing Finn Hammers homemade
> variac inspired me to dig up the remains to see if it would be
> possible to rebuild. I took all of the stuff off except for the core
> and windings, and the physical specs of the core are as follows:
> height=2.9", ID=2", OD=4.1". It is wound 45 turns until the first tap
> point, 206 turns in between the two tap points, and 45 more turns
> until the last turn. The inside is two layered, but the outside is
> single layered (because the inside radius is ~ half the outside
> radius.) I plan to figure out the type of wire and re-wind it in the
> same manner as it was wound. would this work, or is there any other
> way i should go? Any help would be much appreciated. Thanks

Sure, if you use the same wire size, you can rewire the entire core, and it 
will work. You could of course also opt to replace only the burned-out 
sections. That might be easiert. Just remember to properly clean the areas 
around the burns before you add the new wire. For exmple with a toothbrush 
etc and some alcohol or dishwashing liquid, because if there's still burned 
gunk around there then that spot is, for some reason, more likely to burn 
up again. Some sanding paper should be ok to flatten out the top layer, so 
the contactor moves properly. I've found that hammering it down/flat works 
well, too - at least on a single-layer wound variac. YMMV....

cheers,
 - Jan

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 Helsinki University of Technology
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