Re: troubleshooting tesla coil, continued (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 17 Sep 2007 11:02:14 +0100
From: Tom Trevethan <t.trevethan@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: troubleshooting tesla coil, continued (fwd)

The DC resistance of iron/steel is not to high, but because it is 
ferromagnetic
it experiences magnetic hysteresis with AC
(http://en.wikipedia.org/wiki/Magnetic_hysteresis). At RF frequencies 
and tesla
coil currents, steel will dissipate a lot of energy.

 From my limited experience, a little bit if steel is OK in the primary 
circuit,
but not the primary coil. Maybe this is because of the higher magnetic fields.
My steel primary would nearly be hot enough to burn me after a few seconds of
operation. (you could check this - obviously remembering to discharge your cap
:)

As for the tap - I just continued to use a alligator clip without problems.
Although something you could make out of copper would be better.

Cheers,

Tom

Quoting Tesla list <tesla@xxxxxxxxxx>:

>
> ---------- Forwarded message ----------
> Date: Sun, 16 Sep 2007 16:32:38 -0400
> From: Marko Ruban <Marko@xxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: troubleshooting tesla coil, continued (fwd)
>
> It is made of steel wire :) actually.  And thanks for noting that.
>
> I do have 1/4" copper tubing available to make a new primary, but I
> didn't think performance would be effected THAT much.  Can you briefly
> tell me why steel is bad for this purpose?
>
> Can you hint how to tap onto the copper tubing?  Is it just an alligator
> clip?  Does the tap have to be bolted on?
>
> Thanks
>
>
> Tesla list wrote:
>
> ---------- Forwarded message ----------
> Date: Sun, 16 Sep 2007 13:12:26 +0100
> From: Tom Trevethan <t.trevethan@xxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: troubleshooting tesla coil, continued (fwd)
>
> Hi Marko,
>
> What kind of wire is your primary coil made from? I ask because from
> the picture
> it doesn't look like copper. For my first coil I made a primary very
> similar to
> yours (helical) and with thick steel wire - which is now know is bad. Spark
> output was about 1 in. When I replaced this with a flat spiral coil made from
> thin copper tube, output increased to about 18 in.
>
> Cheers,
>
> Tom
>
> Quoting Tesla list <tesla@xxxxxxxxxx>:
>
>
>
> ---------- Forwarded message ----------
> Date: Thu, 13 Sep 2007 19:19:45 -0400
> From: Marko Ruban <Marko@xxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: troubleshooting tesla coil, continued
>
> Hello guys, I'm back from a long summer vacation.  As per previous
> suggestions I have acquired an old NST transformer (12kV, 60Hz, 60mA
> output).  And the spark gap does run now with capacitor/primary in
> circuit.  However, there's no visible effect on the topload, still.
> Could it be that badly un-tuned?
>
> Please see the photo of my simple setup and make any suggestions...
> http://marko.dppl.com/TC_setup.jpg
>
> The flat rectangular thing in front, is the capacitor, which should be
> about 7pF.  Can't make a more specific measurement since my new
> multimeter is still in the mail.  Spark gap is on top of the NST, and
> consists of two screws facing each other (about 0.2" adjustable
> spacing).  Wire running in the back to the right is the ground.
>
> Also, here's a dump of JavaTC for my coil...
> http://marko.dppl.com/coil.txt
>
> Thanks in advance for any assistance.
>
>
>
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>



-- 
Dr Thomas Trevethan
London Centre for Nanotechnology
and Department of Physics and Astronomy
University College London
e-mail: t.trevethan@xxxxxxxxx
Tel: 07952934327