Re: capacitive pole pig ballast

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Jim Lux <jimlux-at-earthlink-dot-net> 

At 11:36 AM 1/8/2004 -0700, you wrote:
>Original poster: Ed Phillips <evp-at-pacbell-dot-net>
>Tesla list wrote:
> >
> > Original poster: "Mccauley, Daniel H" <daniel.h.mccauley-at-lmco-dot-com>
> >
> > Forget the capacitors.  If you are looking for a simple, low-cost,
> > no-frills 3 kVA ballast, then the
> > 500ft roll of 12 AWG wire from Home Depot or similar will do the trick
> > every time.
> >
> > Dan
> >
> >  > Could someone tell me how many .9uf  MO caps it would take to
> >  > ballast a
> >  > 10kva 14400v pig for 3 kva
> >  >
> >  > Thanks
> >  > Steve
>
>         I've never understood "capacitive ballasting".  Resistive or 
> inductive
>yes, but seems to me capacitors in the circuit work in the wrong
>direction.
>
>Ed

Well.. all you want is some reactive voltage drop for 
ballasting.  Traditionally, that's been inductive (for a variety of 
reasons..), but capacitors should work just fine for the voltage control 
kind of function.  They're used in some consumer equipment as a 
inexpensive,high isolation technique to get low voltage at low power from 
the AC line (X-10 modules are a good example)

I don't know that they would work well in situation driving a negative 
resistance (like an arc).. Would there be some sort of weird effect from 
the phase being opposite? (leading current instead of lagging...)

For welders, you already have to have a transformer, so using inductive 
ballasting by changing the leakage inductance is a low cost way to do it.

Likewise, for fluorescent or gas discharge lamps (Neon Signs?) you already 
have to have a transformer to get the voltage up to striking potential, so, 
again, inductively ballasting by increased leakage inductance is easy.