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

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

How would one use a double (or triple) stack? I assume
they are run in parallel? I'm also assuming they
wouldn't need paralleling chokes in this
configuration?

thanks
Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Barton B. Anderson"
> <bartb@xxxxxxxxxxxxxxxx>
>
> Hi Aaron,
>
> Congrats on the variac! But, if it's a 45A variac, I
> wouldn't
> recommend cutting the core unless you actually begin
> to run into
> saturation (and then I'd recommend a double stack).
> I did cut the
> core in my variac, but only because it is a single
> 28A variac
> ballast. I did this early on, not realizing that I
> should have just
> picked up the other 2 variacs (which were only $45
> ea). Yep, live and
> learn. If I had it to do again, I wouldn't. You may
> want to sell it
> someday and it would be best to sell it without a
> slit core.
>
> Take care,
> Bart
>
> Tesla list wrote:
>
> >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
> >
> >
> >