Re: [TCML] Permanent Magnet GDT(?)

[Steve Ward <steve.ward@xxxxxxxxx>]

Christopher,

This will not work as you expect.  Because of the field orientation within
the material itself, the permeability is very low (ideally near 1), whereas
un-saturated ferrite is often a permeability of a few thousand.  So unless
your magnetizing force (amp-turns) is very large, the core will not offer
much permeability, and consequently the leakage inductance will be large,
and the magnetizing inductance will be small, which makes for a poorly
performing GDT.

from your other email you said:

"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?"

True, but you need a lot of field to do that, as permanent magnets are as
saturated as they get typically.  You wouldnt normally ever run a
transformer on that part of the B-H curve, its pointless because the slope
says the permeability is near 1.

I think that also, the material type is specifically designed to have a
large hysteresis, such that it *retains* its magnetism after the original
magnetizing force is removed.  This would be another big strike against it
in terms of using this material as a transformer, the energy loss per cycle
would be problematic.

Steve

On Mon, May 30, 2011 at 2:48 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.
>
>
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