A Ballast Mystery

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

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

OK List Gurus,

Here's a puzzle for you. I've been corresponding with
Greg Peters about arc welder ballast for a
distribution transformer. Our experiences conflict so
badly, I just couldn't leave it alone. I dragged out
my DMM, removed the cover from my welder...

http://hot-streamer-dot-com/greg/buzbox.htm

...and made some measurements.

This is the common setup with the welder primary and
pole xfmr LV winding in series.

1) with the welding leads OPEN, the pole xfmer HV
horns OPEN, and the shunts fully inserted, the 240v
current was about 0.15 Amp. No surprise there.

2) with the welding leads OPEN, and the pole xfmr
horns SHORTED together, the 240v current was about 5.5
Amps. (???)

OK kids. With the welder leads open, how did the 240v
current go up?

3) with the welding leads OPEN, and the pole xfmer
horns SHORTED out with an ammeter/DMM, the 11.5KV
current was 0.12 Amp. Power-wise, 240v at 5.5A is
pretty darn close to 11.5KV at 120ma. Still though,
how is the current going up? Why don't the open welder
leads restrict the 240v current to 0.15A?

4) with the welding leads SHORTED, the shunts fully
inserted, and the pole xfmr horns SHORTED with a DMM,
I got 460ma from the 11.5KV horns. I'm sure the 240v
current is too high to safely measure with my 10A max
DMM.

I'm OK with items 1 & 4. Items 2 & 3 have me stumped.
How can adding the inductance of the pole xfmr in
series with the unloaded welder cause the current to
go up? If anything, it should go down! Thoughtful
analysis, educated guesses, and half-baked opinions
are all equally welcome.

Regards,

=====
Gregory R. Hunter

http://hot-streamer-dot-com/greg

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