Ballast and DC?

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

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!