That reference contradicts itself by its ceramic refence point to ;
A *ceramic* is any of the various hard, brittle, heat-resistant and
corrosion-resistant materials made by shaping and then firing a
nonmetallic^[1] <https://en.wikipedia.org/wiki/Ceramic#cite_note-1>
mineral, such as clay, at a high temperature.^[2]
<https://en.wikipedia.org/wiki/Ceramic#cite_note-2> Common examples are
earthenware <https://en.wikipedia.org/wiki/Earthenware>, porcelain
<https://en.wikipedia.org/wiki/Porcelain>, and brick
<https://en.wikipedia.org/wiki/Brick>.
Ferrite is not a non-metallic material. I would advise the wiki to
correct it's mistake. The facts are given
by those expert on the subject that the dielectric molecular alignment
method of heating does not apply to ferrite core heat loss,
since the ferrite core being a high permeability material, already has
its molecules aligned, and therefore no realignment, with its heat
generating resistance being heat produced by the dielectric method is
happening.
You have not referred to any reference stating a ferrite core is a
dielectric.
POWER CONSIDERATIONS
(Iron Powder & Ferrite)
How large a core is needed to handle a certain amount of power? This is
a question often asked, but unfortunately there is no simple answer.
There are several factors involved such as: cross sectional area of the
core, core material, turns count, and of course the variables of applied
voltage and operating frequency.
Overheating of the coil will usually take place long before saturation
in most applications above 100 KHz. Now the question becomes "How large
a core must I have to prevent overheating at a given frequency and power
level? "
Overheating can be caused by both wire and core material losses. Wire
heating is affected by both DC and AC currents, while core heating is
affected only by the AC (induced eddy *currents*) content of the signal.
With a normal sine wave signal above 100 KHz, both the Iron Powder and
Ferrite type cores will first be affected by overheating caused by core
losses, rather than by saturation.
Nothing about dielectric heating here.
Mr Lazy
On 3/9/20 3:31 pm, David Gilbert wrote:
If you weren't so stubborn (or lazy) you could have easily found this
reference on Wikipedia:
"A *ferrite* is a ceramic material made by mixing and firing large
proportions of iron(III) oxide (Fe_2 O_3 , rust) blended with small
proportions of one or more additional metallic elements, such as
barium, manganese, nickel, and zinc."
https://en.wikipedia.org/wiki/Ferrite_(magnet)
Note the term "*ceramic*". In what world do you live where ceramics
don't have dielectric properties? Ever heard of ceramic capacitors?
A simple Google search for "dielectric properties of ferrites" (of
which of course there are many varieties) turns up this sampling of
references out of a total of approximately *1,230,000* hits:
https://ieeexplore.ieee.org/abstract/document/4051871
https://www.sciencedirect.com/science/article/abs/pii/S0925838809002084
https://pdfs.semanticscholar.org/9298/4f47d7c6060357c3f8c39bc142911960c5cf.pdf
(scroll down to page 58)
https://aip.scitation.org/doi/abs/10.1063/1.4792494?journalCode=jap
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.416.6977&rep=rep1&type=pdf
https://iopscience.iop.org/article/10.1143/JJAP.10.1520/meta
https://ieeexplore.ieee.org/document/4051871
https://www.hindawi.com/journals/jnp/2016/4709687/
http://www.bjp-bg.com/papers/bjp2018_1_044-053.pdf
http://www.ijera.com/papers/Vol7_issue2/Part-5/I0702054348.pdf
http://chalcogen.ro/265_Farid.pdf
Every one of those links talks about the dielectric properties of
ferrites.
Dave AB7E
On 9/2/2020 9:47 PM, Adrian wrote:
Please quote your online reference please regarding ferrite cores
being a dielectric
If so then my not just use un-enammeled wire on a course wound core ?
A dielectric is an insulator ;
Dielectric
From Wikipedia, the free encyclopedia
Jump to navigation
<https://en.wikipedia.org/wiki/Dielectric#mw-head>Jump to search
<https://en.wikipedia.org/wiki/Dielectric#searchInput>
Not to be confused withDielectric constant
<https://en.wikipedia.org/wiki/Dielectric_constant>orDialectic
<https://en.wikipedia.org/wiki/Dialectic>.
A*dielectric*(or*dielectric material*) is anelectrical insulator
<https://en.wikipedia.org/wiki/Insulator_(electricity)>
I don't see any reference to ferrite cores being a dielectric online.
The molecular alignment heating method regarding dielectric loss, is
not mentioned on any ferrite core RF heating science, that I can find.
Please read ;
Predicting Temperature Rise of Ferrite Cored Transformers George
Orenchak TSC Ferrite International 39105 North Magnetics Boulevard
Wadsworth, IL 60083
"Core Losses Core losses are a significant contributor to the
temperature rise of a transformer. Hysteresis loss, eddy *current*
loss and residual loss all contribute to the total core loss. At high
flux densities and relatively low frequencies, hysteresis losses are
usually dominant. Hysteresis loss is the amount the magnetization of
the ferrite material lags the magnetizing force because of molecular
friction. The loss of energy due to hysteresis loss is proportional
to the area of the static or low frequency B-H loop. At high
frequencies, eddy current losses usually dominate. Eddy *current*
loss is from a varying induction that produces electromotive forces,
which cause a current to circulate within a magnetic material. These
eddy *currents* result in energy loss. Understanding the behaviour of
the combined total core loss as functions of flux density and of
frequency is most important. "
Dielectric is not mentioned.
On 3/9/20 2:15 pm, David Gilbert wrote:
If you weren't too stubborn you could find many, many online
references to the dielectric characteristics of ferrites. A ferite
core absolutely IS a dielectric. There is nothing false about what
I've been telling you.
Dave AB7E
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