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Re: Question about ballasting and VA

Hi all,

 I have been reading this thread with some interest as I too vary my coil
using a
large variac
to control current. Last night I went and spent considerable time dialing in
various levels of
current, (my meters show V and A to the transformer), at a certain point
the spark
gap becomes
markedly brighter however the arc lengths do not increase in length but
there is
some
increase in activity although this may be subjective as I am looking at the
meters,
the gap, and the arcs
somewhat at the same time, (multitasking :-)),. The point is that I can still
increase current but all that happens is
sporadic firing of the safety across the gap.

Regards

 Robi Copini in OZ.



Tesla List wrote:

> Original Poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
>
> > Original Poster: "Ross Overstreet" <ross-o-at-mindspring-dot-com>
>
> Hi Ross,
>
> I do use inductive ballasting and I haven't (maybe others have) found that my
> variac acts as an impedance matching component. I do notice that there is a
> maximum amunt of current that the coil won't process further. However,
turning
> up my variac beyond this point does not reduce my spark length (like
turning it
> down will). On the other hand, my input current will climb and if I keep
going,
> I will pop the breakers even though the spark length doesn't increase. To me,
> it is acting as a simple current limiter. It can appear magical when I start
> increasing the current until the point of takeoff. When your turning it up,
> there is a point where you start charging the caps to a potential to conduct
> consistently at the gap rate. Thats when the sparks really fly and best arc
> lengths are achieved. However, as I said, increasing current hasn't shown
> itself in a decrease in spark length - just input current going somewhere
other
> than the sparks. At least, that's what I've seen thus far and it "appears" as
> though the coil itself just cannot process further current into spark lengths
> without making some kind of change to the coil itself.
>
> Bart
>
> > Hi Bart,
> > I'm not even sure what I am trying to say, probably shouldn't be wasting
> > bandwidth...
> > I'm in over my head here.  I haven't studied it enough or ran any
> > simulations.  I'm fortunate enough to hang out with some guys who run big
> > coils and operating procedures made me rethink what the series variable
> > inductor that everyone calls the "current limiting" variac is doing.
> >
> > The current limiting variac certainly doesn't behave as a big Tesla Coil
> > "dimmer".  There is a definite "sweet spot" on the variac that seems almost
> > magical.  Richie's variable inductor report is outstanding (as usual), but
> > I'm not convinced that this is the same phenomena that is making the big
> > coils run smoothly.
> >
> > I was hoping that some modeling had been done in this area or that someone
> > had an intuitive explanation that my simple mind could grasp.
> >
> > Thanks,
> > Ross-O