Losses in balun cores
 

I recently saw an article with the following:

"I would like to express my thanks to xxxxxxxx for continuing the
advancement of the transmission line transformer. We have become somewhat
of co-workers, sharing information back and forth about how these efficient
devices work in the HF, MF, and VHF parts of spectrum. He has done some
recent experiments on new ferrite cores and found that by reducing the
number of turns the actual potential difference on each turn is greater
which increased the core loss. This means that the losses in these
transmission line transformers are voltage dependant and not flux related."

I am trying to understand how it is that losses are "voltage dependant and
not flux related". Aren't flux and voltage related? Is he trying to say
there are core losses that result from a voltage impressed across the
winding, but the losses are caused mainly by electric field rather than the
magnetic field? My understanding was that whilst there are dielectric
losses in ferrite and iron power materials, the magnetic losses dominate in
most applications.

Is there a sound basis for the quote, or is it advertising bunk?

Owen

Losses in balun cores
 

On Wed, 23 May 2007 22:08:31 GMT, Owen Duffy wrote:


I recently saw an article with the following:

"I would like to express my thanks to xxxxxxxx for continuing the
advancement of the transmission line transformer. We have become somewhat
of co-workers, sharing information back and forth about how these efficient
devices work in the HF, MF, and VHF parts of spectrum. He has done some
recent experiments on new ferrite cores and found that by reducing the
number of turns the actual potential difference on each turn is greater
which increased the core loss. This means that the losses in these
transmission line transformers are voltage dependant and not flux related."

I am trying to understand how it is that losses are "voltage dependant and
not flux related". Aren't flux and voltage related? Is he trying to say
there are core losses that result from a voltage impressed across the
winding, but the losses are caused mainly by electric field rather than the
magnetic field? My understanding was that whilst there are dielectric
losses in ferrite and iron power materials, the magnetic losses dominate in
most applications.

Is there a sound basis for the quote, or is it advertising bunk?

Owen

Sounds like nonsense to me Owen. The only losses of any importance for
baluns that I am aware of are IR losses and flux loss and sometimes
dielectric losses may be significant.

Danny, K6MHE

Losses in balun cores
 

Danny Richardson wrote in
:

On Wed, 23 May 2007 22:08:31 GMT, Owen Duffy wrote:


I recently saw an article with the following:

"I would like to express my thanks to xxxxxxxx for continuing the
advancement of the transmission line transformer. We have become
somewhat of co-workers, sharing information back and forth about how
these efficient devices work in the HF, MF, and VHF parts of spectrum.
He has done some recent experiments on new ferrite cores and found
that by reducing the number of turns the actual potential difference
on each turn is greater which increased the core loss. This means that
the losses in these transmission line transformers are voltage
dependant and not flux related."

I am trying to understand how it is that losses are "voltage dependant
and not flux related". Aren't flux and voltage related? Is he trying
to say there are core losses that result from a voltage impressed
across the winding, but the losses are caused mainly by electric field
rather than the magnetic field? My understanding was that whilst there
are dielectric losses in ferrite and iron power materials, the
magnetic losses dominate in most applications.

Is there a sound basis for the quote, or is it advertising bunk?

Owen

Sounds like nonsense to me Owen. The only losses of any importance for
baluns that I am aware of are IR losses and flux loss and sometimes
dielectric losses may be significant.

Danny, K6MHE


Hi Danny,

It doesn't seem to make sense.

I guess I am not encouraged to buy his book to find out more!

Owen

Losses in balun cores
 

Hi Danny,

It doesn't seem to make sense.

I guess I am not encouraged to buy his book to find out more!

Owen

Owen, you may find this of interest:

http://standards.ieee.org/reading/ieee/ept/trans.pdf
trans.pdf (application/pdf Object)

Sevick's briefly discusses
voltage-dependency of ferrite losses.

Chuck

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Losses in balun cores
 

Chuck wrote in
:


Owen, you may find this of interest:

http://standards.ieee.org/reading/ieee/ept/trans.pdf
trans.pdf (application/pdf Object)

Sevick's briefly discusses
voltage-dependency of ferrite losses.

Chuck

Thanks Chuck,

My original quote was from Sevick, and the following paragraph from your
reference illustrates the predominantly dielectric loss theme:

"Probably the most difficult (and controversial) specification to
establish for these devices is the power rating. The loss mechanism is
completely different from that of the conventional transformer, which is
current-dependent (hysteresis, wire, and eddy-current losses). With these
broadband devices, which mainly use ferrite cores or beads, the losses
are voltage-dependent (a dielectric-type loss). Therefore, higher-
impedance devices or devices subjected to mismatched loads of higher-
impedances, have larger voltage gradients along their transmission lines,
and hence, more loss."

Other works that I have read describe the loss mechanisms as quite
complex; magnetic loss described by a complex mu value that is
temperature, frequency and flux dependent, resistive loss in the core
material, dielectric loss in the core material, and resistive loss in the
conductors. Sevick seems to say that only one of these is relevant, or
that loss can be simplfied to a single equivalent loss, the dielectric
loss.

I guess it is appealing to equate loss that increases with frequency to
an equivalent dielectric effect, but the loss is flux dependent and in a
non-linear way, so it doesn't seem to fit well with a simple dielectric
equivalence.

Owen

Losses in balun cores
 

Owen Duffy wrote:
Chuck wrote in
:


Owen, you may find this of interest:

http://standards.ieee.org/reading/ieee/ept/trans.pdf
trans.pdf (application/pdf Object)

Sevick's briefly discusses
voltage-dependency of ferrite losses.

Chuck

Thanks Chuck,

My original quote was from Sevick, and the following paragraph from your
reference illustrates the predominantly dielectric loss theme:

"Probably the most difficult (and controversial) specification to
establish for these devices is the power rating. The loss mechanism is
completely different from that of the conventional transformer, which is
current-dependent (hysteresis, wire, and eddy-current losses). With these
broadband devices, which mainly use ferrite cores or beads, the losses
are voltage-dependent (a dielectric-type loss). Therefore, higher-
impedance devices or devices subjected to mismatched loads of higher-
impedances, have larger voltage gradients along their transmission lines,
and hence, more loss."

Other works that I have read describe the loss mechanisms as quite
complex; magnetic loss described by a complex mu value that is
temperature, frequency and flux dependent, resistive loss in the core
material, dielectric loss in the core material, and resistive loss in the
conductors. Sevick seems to say that only one of these is relevant, or
that loss can be simplfied to a single equivalent loss, the dielectric
loss.

I guess it is appealing to equate loss that increases with frequency to
an equivalent dielectric effect, but the loss is flux dependent and in a
non-linear way, so it doesn't seem to fit well with a simple dielectric
equivalence.

Owen

Owen, I didn't see any reference in
Sevick's fourth edition to the
voltage-dependency of core losses.

Instead, the following quote seems to
characterize his philosophy in the book:

"With transmission lines, the flux is
effectively canceled out in the core and
extremely high efficiencies are possible
over large portions of the
passband--losses of only 0.02 to 0.04 dB
with certain core materials.

Therefore, the power ratings of
transmission line transformers are
determined more by the ability of the
transmission lines to handle the
voltages and currents than by the size
and conventional properties of the core."

He is unambiguous in arguing that there
is a significant lack of understanding
of the differences between conventional
transformers and transmission line
transformers.

This edition has a copyright date of
2001 whereas the IEEE paper is dated 1993.

Hope that helps.

Chuck






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Losses in balun cores
 

On Sat, 26 May 2007 20:51:37 -0400, Chuck
wrote:

Owen Duffy wrote:
Other works that I have read describe the loss mechanisms as quite
complex; magnetic loss described by a complex mu value that is
temperature, frequency and flux dependent, resistive loss in the core
material, dielectric loss in the core material, and resistive loss in the
conductors. Sevick seems to say that only one of these is relevant, or
that loss can be simplfied to a single equivalent loss, the dielectric
loss.

He is actually distinguishing between transformer type losses (as
Chuck notes later in material I have not quoted). In the conventional
transformer, loss is Ohmic due to the circulating eddy currents. This
explanation does not serve Ferrite, which is principally an insulator,
a dielectric with magnetic properties. Further, the operation of
transformation for conventional transformers is through magnetic
coupling, that is not so for tranmission line transformers (that no
doubt all parties here are already aware of, and which Sevick is
distinguishing to the naive readers of his paper). Hence, he is
responding to loss issues that are found in conventional designs, but
missing (or rather optimized for the Common Mode) in our chokes or
BalUns.

I guess it is appealing to equate loss that increases with frequency to
an equivalent dielectric effect, but the loss is flux dependent and in a
non-linear way, so it doesn't seem to fit well with a simple dielectric
equivalence.

Ferrites are not simple dielectrics, not even linear as a class (but
seemingly so for our limited applications as chokes).

Owen, I didn't see any reference in
Sevick's fourth edition to the
voltage-dependency of core losses.

I can observe it in the reference offered. However, Sevick couches
this dependency parenthetically to the dielectric property. As this
is specifically true, and he distinguishes other losses in
conventional transformers as Ohmic, his statement in its full context
is valid if perhaps too sparse. It is quite obvious that voltage and
current (and thus flux) are irrevocably inseparable and yet the loss
does not specifically arrive due to conduction in the Ferrite
material.

On the other hand, discussion of Ferromagnetics is couched in magnetic
fields and electron spin, not in voltaics.

Instead, the following quote seems to
characterize his philosophy in the book:

"With transmission lines, the flux is
effectively canceled out in the core and
extremely high efficiencies are possible
over large portions of the
passband--losses of only 0.02 to 0.04 dB
with certain core materials.

The flux of Owen's contention is not the flux of the differential
currents, but of the Common Mode current. [or so I read his query -
at least insofar as the application of the choke serves]

For student of the microwaves, Ferrites offer far more unique
properties than are made use as I've suggested above. The
nonlinearity is that Ferrite can be remarkably transparent to flux of
a given polarization, and with a shift in that polarization it becomes
quite opaque. In this service, it is also characterized as a
non-reciprocal attenuator. This attribute can be modulated,
literally, with an external DC (actually low frequency AC) field to
impart modulation to what would otherwise be a CW signal.

Ferrites employing this polarization characteristic are used in what
are called Faraday Isolators (another one of those devices that could
be used to separate forward and reverse waves; however, having only
two ports so as to not be confused with the rat-race, and to my
knowledge wholly unknown in this group).

73's
Richard Clark, KB7QHC

Losses in balun cores
 

On Sun, 27 May 2007 00:47:15 -0700, Richard Clark
wrote:

the loss
does not specifically arrive due to conduction in the Ferrite
material.

On the other hand, discussion of Ferromagnetics is couched in magnetic
fields and electron spin, not in voltaics.

As a side-bar, much the same could be said of distilled water, and the
ice made from it. At the point of freezing, the dielectric constant
AND losses undergo a considerable change - and this is attributable to
flux and polarization issues in much the same way.

73's
Richard Clark, KB7QHC

Losses in balun cores
 

On Sun, 27 May 2007 00:47:15 -0700, Richard Clark
wrote:
[snip]

|Ferrites employing this polarization characteristic are used in what
|are called Faraday Isolators (another one of those devices that could
|be used to separate forward and reverse waves; however, having only
|two ports so as to not be confused with the rat-race, and to my
|knowledge wholly unknown in this group).
|

Hmmm.

Losses in balun cores
 

On Sun, 27 May 2007 14:43:17 +0000, Wes Stewart *n7ws*@ yahoo.com
wrote:

On Sun, 27 May 2007 00:47:15 -0700, Richard Clark
wrote:
[snip]

|Ferrites employing this polarization characteristic are used in what
|are called Faraday Isolators (another one of those devices that could
|be used to separate forward and reverse waves; however, having only
|two ports so as to not be confused with the rat-race, and to my
|knowledge wholly unknown in this group).
|

Hmmm.

OK, perhaps known to you and Jim (yet and all, neither of you have
made the arguments that would have stoked that bonfire).

73's
Richard Clark, KB7QHC