Transformer core considered as a waveguide

In summary, the conversation discusses the idea of using the iron core of a transformer as a transmission line or waveguide, but it is noted that this does not fit with the concept of a Goubau line. The magnetic field in the iron core is longitudinal, while the electric field in the Goubau line is longitudinal. It is also mentioned that the operation of a transformer is different from that of a Goubau line, as it is short compared to the wavelength. The idea of treating a Goubau line as a transformer is questioned and the concept of near field effects is brought up.
  • #1
tech99
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Has anyone considered the iron core of a transformer to act as a transmission line or waveguide, where it conveys energy from primary to secondary? The core seems to resemble a "magnetic version" of the single wire Goubau line.
 
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  • #2
Skimming the Goubau line article I note that there is a dielectric coating and the UHF signal is transmitting via surface waves. This does not fit analogously with the transformer core which is being longitudinally polarized. Also you are not getting the propagation down the length of the iron core. Keep in mind that E-M waves propagate transverse to their E and M fields. While the various modes of a wave guide will correspond to different E vs B field directions (as in radial vs circumfrerential or x vs y ) they still invariably align perpendicular to the propagating waves. With the iron core the B field is along the length so one is rather getting "near field effects" with respect to the transmission of power along the core length.
 
  • #3
jambaugh said:
Skimming the Goubau line article I note that there is a dielectric coating and the UHF signal is transmitting via surface waves. This does not fit analogously with the transformer core which is being longitudinally polarized. Also you are not getting the propagation down the length of the iron core. Keep in mind that E-M waves propagate transverse to their E and M fields. While the various modes of a wave guide will correspond to different E vs B field directions (as in radial vs circumfrerential or x vs y ) they still invariably align perpendicular to the propagating waves. With the iron core the B field is along the length so one is rather getting "near field effects" with respect to the transmission of power along the core length.
Thank you for your comments. I had forgotten that the Goubau line was first described with a dielectric coating. For propagation by waveguide modes, I think we can see a longitudinal field component, so B or E may not be perpendicular to the direction of propagation.
For the Goubau line, the magnetic field seems to surround the wire, whilst with the iron core the electric field surrounds the core circumferentially. For Goubau, the electric field is longitudinal and for the iron core the magnetic field is longitudinal. So the fields seem to have the same form but reversed. And when a pulse is applied to the primary, I feel that a wave must propagate along the core to the secondary - it cannot be instantaneous.
Those are my reasons for making the suggestion, and I wondered if a transmission line view (e.g. the effect of mismatching) would be compatible with the basic operation observed with a transformer.
 
  • #4
tech99 said:
when a pulse is applied to the primary, I feel that a wave must propagate along the core to the secondary - it cannot be instantaneous.
?? what if primary and secondary are a bifilar arrangement instead of two coils separated as on a bobbin wound ?
Then it'd work without an iron core.http://amasci.com/tesla/tmistk.html
 
  • #5
jim hardy said:
?? what if primary and secondary are a bifilar arrangement instead of two coils separated as on a bobbin wound ?
Then it'd work without an iron core.http://amasci.com/tesla/tmistk.html
It seems that in the case of two coils spaced by air, we are linking the two transducers together via "free space", so we do not have waveguide propagation. The iron core enables the coils to exchange energy when spaced apart, by acting as a waveguide.
 
  • #6
It does not act like a waveguide in that the mathematical representations of waveguide propagation do not apply. It is a completely different mechanism (magnetic coupling) as opposed to wave propagation (and the associated Modes).

Just because there is energy across a distance in the two cases does not mean they are in any way analogous. Like comparing a wire to a laser.
 
  • #7
A Goubau line is a traveling wave structure. Launching it involves a conical matching section at each end and it operates over many wavelengths. That's very different from the operation of a transformer which is short compared with the wavelength involved. There are parallels between the two, of course, because they both work with EM but I have to ask Why would one want to treat them the same? Would you consider analysing a Goubau line as a kind of Transformer? I can only see a lot of grief in that direction.
 
  • #8
I certainly may be way off with respect to the issue of longitudinal modes but I would agree with sophiecentaur, that wavelength considerations invalidate the treatment of the core as a waveguide. That is what I was thinking with my "near field" comment.
 

What is a transformer core?

A transformer core is a component of a transformer that is responsible for transferring energy from one circuit to another through electromagnetic induction. It is typically made of a ferromagnetic material such as iron or steel.

How does a transformer core function as a waveguide?

A transformer core is designed to guide and direct electromagnetic waves through its core. As the magnetic field created by the input current passes through the core, it induces a current in the secondary winding, allowing for the transfer of energy.

What are the advantages of using a transformer core as a waveguide?

Using a transformer core as a waveguide allows for efficient energy transfer due to the high permeability of the core material. It also eliminates the need for physical connections between the primary and secondary circuits, reducing the risk of electrical hazards.

Are there any limitations to using a transformer core as a waveguide?

One limitation of using a transformer core as a waveguide is that it is only effective for low-frequency signals. At high frequencies, the core material can become saturated, reducing its ability to guide electromagnetic waves.

Can a transformer core be used as a waveguide in all types of transformers?

No, not all transformers use a core as a waveguide. Some transformers, such as air-core transformers, do not have a core and instead rely on the proximity of the primary and secondary windings to transfer energy through electromagnetic induction.

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