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Re: Variac rebuild



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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