RE: [TCML] Ballast Inductor Question

["Jim Mora" <wavetuner@xxxxxxxxx>]

Hi Stefan,

David Rubien has pointed out well, and he controls some pretty very big
power- you need big iron! The core will saturate and will basically go away.
I think you should look for a 20KVA low voltage single phase distribution
transformer. At today prices, aluminum windings are fine. With luck, one of
the single phase windings will be what you need, other wise, its not a lot
of windings to make you own and scrap what you cut off. I have experimented
paring down 3P transformers ; but the results were less than friendly to the
desired target, YMMV -Love to know if you have success with this.

In the US, I think we ballpark 3"^2/ amp as a ballpark figure. Of course you
need enough winding window length for the wire (there is a simple formula
for this as well). The winding length has nothing or little to do with the
current load unless we make a very long core... It should be easy to
compensate with simple arithmetic for 50 Hz. After lots of playing around, I
have settled on rated saturable reactors (very cool) or actuacted slide
chokes. A big core single phase would work too, but is not so versatile or
easily controlled.

Please be carefull,
You vision of pig iron concerns me for your safety in this area.

Best
Jim Mora, Ca, US

s-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of teslalabor@xxxxxxxxxxx
Sent: Thursday, February 25, 2010 4:46 AM
To: tesla@xxxxxxxxxx
Subject: [TCML] Ballast Inductor Question

Hi,

I want to build a new ballast inductor for my big coil. It runs on 400V
2phase at arround 60-80A, 50Hz (Germany) using a bank of 12 or
16 potential transformers, voltage controlled via variac.

I allready have a core for the inductor, but I'm concerned about it's
size. Is it big enough for that power? The core is an U-I type with
adjustable air gap. Its cross sectional size is: 3,15" x 2,36" = 7,4
square inch.

What is the general difference between a small core, which needs more
windings for a given voltage and a bigger core, which needs therefore
less windings? In both cases the current is nearly zero when the gap is
closed and rises, if opened. So why need big cores? I have allready read
here the tumb rule "1kW - 2,5 square inch" or the formula P =
(A/0,16)^2. Following this, for 400V / 60A I would need an VERY VERY BIG
core! So I wonder if I could use my "small" 7,4 sq.inch core.

Coiler Greets from Germany
Stefan



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