Re: Ballast and wire stuff

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

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


     I used Bifilar 12 ga stranded THHN in my ballast, truly bifilar as it's
actually two parallel pairs, and the one pair of windings is used for each leg
to the transformer primary. I figgered this gives a coupla advantages:

-interleaving both pairs maximizes interwinding capacitances (helps filter
the RF just a tiny bit more)

-if one leg of the transformer primary shorts to ground, at least there's a
ballast winding in each of the 240V "hots" to minimize damage. Putting them
both on one big core helps in that event as well...

     I think a pair of 12ga THHN paralleled may be pushing it. After 10
minutes of running the Jacob's ladder, the windings get pretty warm. Not 
dangerously
so, but enough to make you think twice. Three parallel 12 or a pair of 10
would be better.    Core has almost zero temperature rise. I hacked up a 25kVA
480V-480V isolation transformer, cut up the laminates, stacked and interleaved
the pieces, built a mount frame, drilled and thru-bolted the thing into a big
open "E" (no "I" across the top). Good for 55 amps running a Jacob's ladder.
     Keep your clamp-on ammeter about 3 feet away from the ballast when
measuring. Tricky putting it into an enclosure, as it inductively heats 
sheet metal
within half a foot pretty well.

-Phil LaBudde