Re: [TCML] Magnifiers and transients

["Dex Dexter" <dexterlabs@xxxxxxxxxxx>]

That's very interesting.
I wonder if these transients ripples can trigger racing sparks.

Dex


--- tcml88@xxxxxxxxxxx wrote:
>
From: Paul Nicholson <tcml88@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: [TCML] Magnifiers and transients
Date: Sun, 21 Feb 2010 23:57:45 +0000

Here is a 2-coil TC, conventional flat spiral primary placed
just below the secondary, k=0.12,

Waveforms and animation,

  http://abelian.org/tssp/tmp/c1.wave.gif
  http://abelian.netcom.co.uk/tssp/tmp/c1.anim.gif

And the voltage gradients along the secondary,

  http://abelian.netcom.co.uk/tssp/tmp/c1.grad.gif

Not much excitement there.   The two 1/4 wave modes share
almost equally 99.8% of the firing energy.  The tiny remainder
ends up in the HF transient that you can see most clearly in
the gradient animation travelling up and down the secondary.

The voltage gradient due to this transient alone is easier to
see if I remove the two operational resonances,

  http://abelian.netcom.co.uk/tssp/tmp/c1.trans.gif

In this example it kicks up to about 6 to 8 kV, worse near the
ends of the secondary.   Even though the energy involved is quite
small, it is concentrated spatially and in time.

Raising the primary to just above the base of the secondary,
we obtain k=0.16 and the transient gradient is now

  http://abelian.netcom.co.uk/tssp/tmp/c2.trans.gif

The transient makes a round trip of the secondary in about 3uS,
after which it decays due to losses and dispersion.

Raising the primary further still increases the coupling to
0.2 and with this setting (primary about 10% of the way up the
secondary), we have 0.64% of the firing energy in the transient.

  http://abelian.netcom.co.uk/tssp/tmp/c3.trans.gif

But the transient voltage gradient is no longer so high.  Even
though there is more energy in the transient, its frequency
components don't go so high - it is less concentrated.

There seems to be a worst case for this transient voltage
gradient, I'm not sure just where but it probably occurs when
the primary is level with or just above the secondary base.

Experimenters with adjustable primary height, base current
CT and digital scope should be able to confirm this effect by
analysing the HF ripples present in the base current waveform.
>
<snip>   

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