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TIG arc starter inductor and X-ray tubes.
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From: Bill the arcstarter [SMTP:arcstarter-at-hotmail-dot-com]
Sent: Wednesday, February 25, 1998 8:56 PM
To: tesla-at-pupman-dot-com
Subject: TIG arc starter inductor and X-ray tubes.
Coilers,
I measured the inductance of that TIG arc initiator coupling coil.
This is 10 turns of #18 magnet wire, about 5/8 diameter, and about
4 inches long. The inductance measures as 1.9 uH w/o the core. All
inductance measurements were performed at a 1KHz test freq.
With the core, it measures a whopping 6.9 uH. So the core has a
net permeability of 3.5 or therabouts. Remember-this was the core
which I x-rayed, and consisted of 5 small ferrite bars in series with
airgaps. Someone on the list (forgot who) thought this bar would have
a low permeability because of the airgaps, and they were right!
In the Hobart welder from which it came, this core was operated in a
quenched-gap configuration with two paralleled 0.004 uf caps, which
works out to a resonant freq of about 600KHz... Bypass caps across
the primary power transformer routed the HV/HF around and into
the metal being welded...
A very far-away picture of this coil (attached to my stick welder) is
on my page at:
http://www.geocities-dot-com/CapeCanaveral/hangar/6160/weld3.gif
All you can see is the outer "power-coil" aluminum helix...
I can only assume the purpose of the core is to distort the flux
return path, so as to actually force it to link with the surrounding
power-coil. Perhaps w/o the core, the flux would hardly extend
beyond the outer envelope of this sparse solenoid and not link to the
power coil. Any comments? Am I deluding myself? :)
Oh, from time to time I can get ahold of used x-ray tubes and the
like. For a nominal fee (basically shipping) I could get an
interested coiler a tube. These are hospital-grade, oil-cooled (via
convection) ~30-60KW tubes with a rotating tungsten target, about the
size of a large loaf of bread. These tubes will be well-used but
generally servicable. Let me know if anyone is looking for this sort
of thing... Otherwise they just go into the trash, which is a crime!
(Someone please tell the HV list too!)
-Bill the arcstarter
Starting arcs in Cinci, OH.
http://www.geocities-dot-com/CapeCanaveral/Hangar/6160
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