On Sun, 11 Jan 2009 22:45:43 -0500, Paul Christensen wrote:
>but I am curious as to why Fair-Rite has no cores in the
>traditional thickness and diameter sizes.
I'll make an educated guess. Fair-Rite makes cores for several
uses. One major uses are inductors and transformers, where they
are mostly working in the range where their resistance is small in
proportion to their inductive reactance (that is, they are
relatively efficient). Another major use is suppression. For the
reasons I've shown, ferrites used for suppression are very lossy
-- they are used at the upper extent of their useful range.
Those familiar "small donuts" are mostly part of the "inductive"
component product group.
You can, for example, find a #43 2.4-inch o.d. toroid (FT-240 in
Amidon-speak) in two different places in the Fair-Rite catalog.
There's one that's specified as an inductive component, and
another that's specified as a suppression component, and different
parameters are specified for the two classes of components. With
inductive components, the emphasis is on mu at low frequencies,
while for suppression components, the emphasis is on minimum or
typical values of impedance at certain frequencies. They may come
off the same product line, with a sort at the end of the line, or
the inductive part may be mfd with a process that results in
tighter tolerances on mu.
Hope this helps.
73,
Jim K9YC
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