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



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 > >