[Milsurplus] Triad Choke

[J. Forster]

Hi Richard,

Swinging chokes are hard to design and do vary quite a bit due to air gap
tolerances. One also has to take into account the compliance of the gap
spacer as the forces can be very large.

On your previous post, it's a clever measurement btechnique. The results
are not perfect, but it should give good approximate results, especially
for unknown choke designs.

Thanks,

-John

=============


> Thoughts on Swinging Chokes:  The only difference between a "standard"
> choke and a swinging choke is the size of the air gap in the core.  Less
> gap, more swing.  Think of the magnetic circuit in the core as analogous
> to voltage drop in Ohm's Law.  The magnetic core has high permeability,
> requiring few ampere-turns, and the air gap has no permeability
> requiring many ampere-turns.  Thus, with a large air gap in the core
> most of the ampere-turns are in the air gap, making it less sensitive to
> dc, and there is not so much change in inductance as dc flows through.
> With the small air gap, more magnetic flux is possible because of the
> lower reluctance of the magnetic path, and the iron part tends to
> saturate more quickly, causing the inductance to swing at high dc
> currents.  Does that make sense?  FYI, it's hard to calculate
> performance because of magnetic fringing at the air gap.
>
> I have found that marked choke inductance is only nominal, and can vary
> significantly depending on how well the core was put together.
> Fortunately it seldom matters.
>
> Richard, AA1P
>
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