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

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

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

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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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 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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