Re: Arc Welders as Rheostats??

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

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

> >         Not that simple by any means.  When the voltage across the
portion of
> > the winding being used exceeds the voltage in normal "variac" operation
> > the core will saturate, and moving the brush only affects at what point
> > in the cycle saturation will occur.  Of course, if the variac core is
> > gapped appropriately, this won't happen but it's real tough to cut those
> > wraps of thin core steel.
> >
> > Ed
> 
> Very true. I wasn't trying to go into what would happen when the core
> saturates, but just give
> a simple idea of the variacs use (consider the question that was asked).
> Regarding the core
> cutting. I've cut a couple variacs (laminated cores and solid composite -
> they come in both
> styles).
> 
> I used a gravity band saw. Lay it in position center of windings and let it
> cut. Takes about 30
> to 40 minutes on a 30A variac. I used ty-wraps to keep the laminations
> together (there are
> filings which find their way into the laminations, but not a big deal). On
> both types, I
> inserted a plastic shim expoxied into position. Rather easy IF you have the
> right equipment.
> 
> Take care,
> Bart

	Fine.  I think a lot of the people here don't understand about core
saturation (for example, can I run my 120 V NST on 2200 V and get 275 kV
out - not too much exaggeration) and need to have it drilled into their
heads to avoid bitter disappointment.  As for the band saw, you must
have mighty fine teeth on a good blade!

Ed