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RE: [TCML] Permanent Magnet GDT(?)
Mike, all,
I understand that the magnetic material is already close to saturation
when fully magnetized, as in a permanent magnet, but can that nearness
to saturation not be reversed by applying an opposition to the current
magnetic field?
Here's a small example to illustrate what's in my mind:
If you bias a core in one direction with a constant DC voltage of 9V (let's neglect current, for our purposes), you get what is akin to a permanent magnet. If you add two windings, one a primary and one a secondary, you will have a total of three windings - 1 = Bias; 2 = Primary; 3 = Secondary
These are the theoretical voltages on each winding, with (2) as the independent variable:
Zero degrees:
1 = 9V+ 2 = 0V 3 = 9V+
Ninety degrees:
1 = 9V+ 2 = 0V- 3 = V0
One-hundred-eighty degrees:
1 = 9V+ 2 = 18V- 3 = 9V-
Two-hundred-seventy degrees:
1 = 9V+ 2 = 18V- 3 = 9V-
(This is assuming a perfect square-wave on winding 2, no losses and no noise created)
I understand that I'm overlooking the fact that current is induced by change in flux and at 270 degrees there hasn't been a change in flux for an entire quarter-cycle, but my thought is that, given sufficient protection to reversals on winding 2, winding 3 would effectively average out the difference.
Thank you, again, for your time,
- Christopher
> Date: Mon, 30 May 2011 22:58:31 -0400
> Subject: Re: [TCML] Permanent Magnet GDT(?)
> From: mdt24@xxxxxxxx
> To: tesla@xxxxxxxxxx
>
> Having a permanent magnet core wouldn't cause any difference on the output
> of the transformer. It simply biases the core material with a large initial
> flux. The AC component of the flux swing would not change, and that
> determines the output. Using a magnetic core would just be likely to
> saturate the core sooner. Also it would probably buzz quite a bit.
>
> -Mike
>
> On Mon, May 30, 2011 at 3:48 PM, Christopher Karr <chriskarr4@xxxxxxxxxxx>wrote:
>
> >
> > Good day, Everyone,
> >
> > I've been pondering this topic for some time, now, and I've been wondering
> > if it were reasonable to use a ferrite permanent magnet (in toroidal shape)
> > as a core for a GDT.
> >
> > My thinking is based on the fact that transformer action is based on
> > changing magnetic flux, so if the primary of such a GDT were driven in a
> > single-ended configuration with the magnetizing current opposing the natural
> > flux of the magnet, during the 'dead time' of the signal, a full
> > flux-reversal would be made, naturally, by the magnetic material. This would
> > - in my mind - give rise to an extremely simple push-pull gate signal.
> >
> > The only problem I see, prior to receiving your answers, is the complete
> > lack of control over one half of the waveform, since it would be determined
> > solely by the properties of the magnetic material.
> >
> > Feel free to make corrections, or even tell me I'm *way* off-base. If I
> > knew for sure, I wouldn't be asking. *wink*
> >
> > Thank you for your time,
> >
> > Best wishes,
> >
> > - Christopher
> >
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