Re: variac amperage control??

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi David, 

I cut the core on a 10A and a 30A variac. It wasn't a problem but only due to
the tool used (a gravity band saw). I cut right down the center of the unwound
area before the connecting plate (swung it out of harms way). It took about 30
minutes of cutting (nice slow pace) but made a clean cut. I epoxied some hard
plastic into the slot to keep the core nice and tight. Worked great! The 10A
core was a solid iron compount. The 30A core was made of laminations. This did
spread a little at the edges as each lamination was cut (filings getting
between laminations. Tie wrapped up then did the smae epoxy thingy to them.
It's been in use about 2 1/2 years and going strong. 

Take care, 
Bart 

Tesla list wrote: 
>
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <Tesla729-at-cs-dot-com> 
>
> In a message dated 2/11/01 10:18:02 AM Pacific Standard Time, 
> tesla-at-pupman-dot-com writes: 
>
> << "Ed Phillips wrote: 
> < Cutting a 
> < thin slot through the core would probably cure the saturation and turn 
> < it into a linear reactor, but have never sacrificed a variac to find 
> < out.  Cutting through that silicon steel ribbon would be a pretty tough 
> < proposition, but think some have reported it. 
>
> Hi Ed, Un-Terry, 
> Yep, I can testify to what both of you are saying. I had a 28 amp/240 volt 
> variac that I was using as a current limiter for my a coil a while back and 
> I ended up burning the windings up on a very small area of the variac (< 1").
>
> It was enough to riun the variac, though. Then I decided to take it apart and
>
> salvage the donut core. I then thought about cutting the slot in the variac 
> core for an extra reactor ballast. I first tried with a hacksaw (lol). Not! 
> We're 
> talikng about appr. 2" x 2.5" of solid silicon steel. Then I bought a metal 
> cut- 
> ting blade and installed it on my circular saw and proceeded to cut thru it. 
> By now, it was more of the challenge of actually cutting thru the core than 
> actually being able to get something useful out of it. After about 10 minutes
>
> of a shower of sparks, I finally cut clean thru it, although the edges were 
> rather ragged. Anyway, the core kind of "spring" opened once the cut was 
> completely thru and it left a gap about 2" wide. Also, the lamenations 
> spread out pretty bad around the cut, so I don't know if it's even usuable 
> now and it's pretty doggone ugly :-( 
>
> David Rieben