Thinks, Jim, no the debate is purely about the cause of heat in a
ferrite core balun, not the other things you mention. I use common mode
chokes, and they work well.
From your link ;
"Power Loss Density - P (mW/cm3 ) The power absorbed by a body of
ferrimagnetic material and dissipated as heat, when the body is subject
to an alternating field which results in a measurable temperature rise.
The total loss is divided by the volume of the body. "
Eddy currents induced from that AC field as documented on numerous
previous links , reveal themselves as heatloss and temperature rise,
in differrent amounts depending on the material properties.
Two primary things can cause the core to heat.
1. Resistive losses in the transformer winding wire due to the primary
and secondary currents.
2. Ferrite core loss to to such factors as eddy currents, and magnetic
hysteresis.
I found Barry's link interesting but no mention of heat on the various
sections.
Adrian Fewster
'
On 3/9/20 4:53 pm, Jim Brown wrote:
On 9/2/2020 9:02 PM, Adrian wrote:
A dielectric is defined as an insulator . A ferrite core is not a
dielectric (insulator), This is the false fact in your theory.
You have massive gaps in your understanding of how common mode chokes
work and the properties of ferrite materials. The best technical data
refererence I know of Fair-Rite's catalog, which is online and can be
downloaded as a pdf.
https://ebiz.fair-rite.com/newfair/pdf/Fair-Rite_Catalog_17th_Edition.pdf
The fundamental properties of ferrite materials vary widely depending
on their chemical composition, commonly called "the mix," and each mix
is tailored to a specific range of applications. A table summarizing
those properties begins on page 4 in the print version, page 6 of the
pdf. The resistivity of the materials listed varies over 7 orders of
magnitude, from 50 ohm-cm to 10 exp9 ohm-cm.
My tutorial on how common mode chokes work is here.
k9yc.com/RFI-Ham.pdf
The concepts were added to the ARRL Handbook around 2011. Designs for
practical transmitting chokes are here.
http://k9yc.com/2018Cookbook.pdf
Note that these are not "baluns," a word that describes at least ten
very different physical things, but rather common mode chokes. Their
sole function is to minimize common mode current. They do not do
impedance matching. That function is provided by very different things
best called tranformer baluns, and they come in multiple forms.
Extensive research I published in a peer reviewed AES paper in 2003
found manufacturer's literature from the '50s/'60s indicating that
they understood how common mode chokes work, and after I published my
work to the ham community, an engineering manager from the CIA passed
along to me an unclassified engineering report from the US Army in the
'70s that was in agreement with all of the fundamental concepts I had
published and had developed a family of designs for field use. The
only thing they missed was the property of dimensional resonance,
which I learned about in classic reference a colleague found in the U
of Chicago engineering library. That reference, by E. C. Snelling, is
cited in several of my publications.
73, Jim K9YC
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