RE: Cheap parts for high-power resistive ballast (for pole transformer). (fwd)

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Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 2 Jun 2005 08:26:40 -0700 (PDT)
From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: RE: Cheap parts for high-power resistive ballast (for pole
    transformer).

(this thread is getting long...oh well, the list is
pretty quiet, too)

Okee dokey, I've got my new transformers.  Yes,
there's an "s" on the end there; I picked up two. 
When I got down to the salvage yard and saw how big
and heavy the 50kVA units were, I opted for two 25kVA
units instead.  They'll do the same job but can
actually be moved by a human :)  These 25kVA's are
actually smaller (the cans, that is) than my old
15kVA!  They're also about 20 years younger, which
probably explains it.

Anyway, my intent when I picked up two was to run them
in parallel (or series for nearly 30kV--another bonus
to having two instead of one), but then I had another
thought:  Several people have mentioned using
isolation transformers together with heater elements
to create a sort of hybrid resistive/inductive
ballast.  That is, they talk about putting the
elements in series with one side of the isolation
transformer and the pig in series with the other side.
 Does this really offer any advantages?  Maybe for
Telsa coil operation it could improve the rise time
after the cap discharges...I suppose I can visualize
that...but for a Jacob's ladder?  It's just a
continuous short circuit, so I don't see how this
isolation transformer arrangement accomplishes
anything.  But I thought I'd ask.  Perhaps I could use
the two low-voltage windings of one of the
transformers kind of like an isolation transformer,
with one winding in series with the heater elements
and the other in series with the other pig.  It might
work :)

Regards,
Aaron, N7OE