Re: Ballast and DC?

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

Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bigfoo39-at-telocity-dot-com>

Tesla list wrote:

>Original poster: "PotLuck by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<potluck-at-xmission-dot-com>
>
>Hi List,
>I'm building a ballast and a while ago I heard a whisper about using DC
current
>in a separate winding to vary the inductance? I could incorparate such a
>winding instead of adjusting the air gap if there's merit here.
> 
>And how much DC power ( VA ) would be needed to work with a ballast like the
>one shown at the link?
> 
><http://www.richieburnett.co.uk/inductr.html>http://www.richieburnett.co.uk
>/inductr.html
> 
>Thx all!
>
>
>
>
>
What you are thinking of is what they call a SCR   nooo  not a Silicon 
Controlled recitier...   a Saturable Core Reactor.

It is basically ( hahahaha   basically now thats an understatement)  a 
transformer that is on the verge of saturation and by the use of a dc 
coil on the center leg one can saturate or desaturate the middle core 
leg more or less and control the amount of flux produced by the AC coils 
on the 2 outer legs. ( yup you will need an old 3 phase core to do this 
properly ...  )

I wound one up and almost got it working but the amount of power to 
saturate the center leg was about equal to using a variac on the main 
voltage to control input to the coil ....   All mine ended up being was 
a more complicated control unit compared to just the variac system.


Scot D