[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: power supply questions



Original poster: Tesla729-at-cs-dot-com 

"Tesla list" <tesla-at-pupman-dot-com> wrote:

 >Original poster: Ed Phillips <evp-at-pacbell-dot-net>
 >
 >Tesla list wrote:
 > >
 > > Original poster: dhmccauley-at-spacecatlighting-dot-com
 > >
 > >  > Hello!

Yes, I've tried this before and the saturation was
a REAL problem. I had to use very few of the second
"current" variac's windings to get enough voltage
thru to drive the transformer with any real volt-
age. And when I did this, the "current" variac's
few used windings severely saturated and got that
hot enamel smell as well as smoked the brush quite
rapidly.

Also, it's a lot of trouble to cut a gap in the core
of a 1256 Powerstat's core and unless you take time
to TIGHTLY wrap the core with lots of high strength
fiber tape, the core laminents will sproing apart
when you fianlly do cut thru them (ask me how I know
this :^). IMHO, there are much better alternatives
for ballasting than the second variac.

David Rieben
 > >  >
 > >  > 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
 >
 >
 >