RE: Luxtrol 45A 240V variac as ballast--cutting up core?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "david baehr" <dfb25@xxxxxxxxxxx>


...I havnt had experiance with cuttin' up a Variac,  but, have ya 
tried finding an ol' arc welder ,etc ??   It would be a shame to 
'gap' that variac . I used a standard 240 v welder and it will pass 
up to 70 amps or so .....................once cut, the variac wont be 
a variac anymore, right ??? Heck, I dont know.................:-)


From:  "Tesla list" <tesla@xxxxxxxxxx>
To:  tesla@xxxxxxxxxx
Subject:  Luxtrol 45A 240V variac as ballast--cutting up core?
Date:  Mon, 26 Sep 2005 13:20:07 -0600
>Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
>
>Hey folks!  I recently acquired a Luxtrol 45A 240V
>variac.  I'd like to make it a ballast for a pole
>transformer, and I'm wondering if somebody could share
>an experience:  How shall I go about putting a gap in
>the core?  About how wide should the gap be?  I'm
>thinking of trying to coerce a machinist friend into
>helping me, since I'd like to avoid hours of hack
>sawing by hand! :)
>
>And one related question:  I recently built a water
>resistor (20 gallon garbage can full of doped water
>with copper rods immersed about 1/8th inch apart,
>sliding PVC sheath over one rod to control resistance)
>and have used this to create some nice 20+kW Jacob's
>ladders.  It's obviously quite lossy, but the nice
>thing is that I can ramp the current down to near zero
>before cutting the power, thereby avoiding big
>inductive spikes.  To avoid forfeiting this "feature"
>of the resistor while deliberately forfeiting most of
>the losses, I thought perhaps that I'd put the water
>resistor in between the modified variac and the pig.
>The resistance can then be slowly brought down until
>the majority of the limiting is being done by the
>variac (resistor varies down to about one ohm).  This
>would seem to offer the low losses of an inductive
>ballast while simultaneously allowing nice soft stops
>and starts.  The variac would just be preset to the
>desired operating current and then left alone.
>
>Thoughts on this?
>
>Aaron
>
>