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