Re: power supply questions

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 9/6/03 6:16:52 PM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:


>Original poster: Ed Phillips <evp-at-pacbell-dot-net>
>
>Tesla list wrote:
> >
> > Original poster: dhmccauley-at-spacecatlighting-dot-com
> >
> >  > Hello!
> >  >
> >  > I have two questions about changes I want to make to my power
> >  > supply:
> >  >
> >  > 1st: I only have one variac to controll the main HV transformer.
> >  > Currently I use it in standard configuration and additional
> >  > inductive ballast to limit the current. By means of that I
> >  > experience a lack of output voltage due to the voltage drop in
> >  > the ballast / variac. Can one use the variac to controll the
> >  > current ( in series ) WITHOUT using one to controll voltage?
> >  > Would that give a voltage gain?
> >
> > You can use a variac as a variable inductor.  However, inductance will vary
> > from variac to variac and so will the current ballasting.
>
>     Unless the core is gapped it will act more like a variable saturation
>device than in inductor. As the number of turns is reduced the flux
>density in the core will increase to the point where severe saturation
>will occur.  "A lot of guys are doing it" so I guess that means it
>works, but my guess is they are all way, way into core saturation.
>
>Ed


Ed,

I use a 5,000 watt 120 volt light dimmer variac as primary ballast for my 5 
kva transformer.  Since the variac is rated at 40 amps, I don't think it 
should be saturated when running at about 35 amps.  It does groan 
however.  I have had it set at about 50 %, using the wiper terminal and one 
end terminal.  Since it doesn't seem to make much performance difference as 
to where it is set, and I have seen sparks from the wiper, next time I run 
it I plan to just hard wire to both ends and leave the wiper out of the 
circuit.

Ed Sonderman

Ed Sonderman