Why isn't there a non-conducting core wire for high-frequency coil applicationsDoes solid/multi-stranded/Litz...
Why isn't there a non-conducting core wire for high-frequency coil applications
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Why isn't there a non-conducting core wire for high-frequency coil applications
Does solid/multi-stranded/Litz wire make a difference in binary serial output?Is the skin effect a factor for low-current AC applications?Would using litz wire for an inductor change the inductance compared to regular wire?Can I build a high-frequency SMPS choke out of an arbitrary coil of wire?Winding my own inductor-resistanceSpaced air core inductor wire size effect?Does stranded wire reduce resistance from skin effect when strands are not insulated?Choosing a wire diameter for an inductorInterleaving in litz wire transformer - to be or not to be?Skin effect with superimposed frequencies
$begingroup$
Background
The commonly known skin effect formulas are derived and only apply to solid conductors. The commonly used "skin depth" only applies in these cases. It is for this reason that in some applications tubes are used, as these are much more weight-efficient than the same diameter wire at a high-enough frequency.
At 1MHz the skin depth of copper wire is 65µm which means that only 40% of the volume of a 1mm diameter wire is carrying 95% of the current, with >35% of it in the outside 20%.
From the skin-depth formulas it is known that a lower conductivity material (e.g., aluminum) has a skin depth that is considerably larger than a higher conductivity one (e.g., copper). As the formula predicts, skin depth is inversely proportional to the square root of the conductivity. If we carry this to its logical consequences, it should be the case that for a conducting tube (which has an insulation core) skin depth should be larger than for an equivalent solid conductor.
As an alternative intuition a thin-walled insulated-core conductor would have nearly twice the surface area of a solid conductor. So it should asymptotically approach nearly half the resistance at a high enough frequency.
In effect, as can be seen in this paper from HB Dwight in 1922 (possible paywall), the increase in resistance w.r.t. frequency for a tube whose wall thickness is 20% of its diameter is more than a factor of two lower than for a solid wire.
From the above curves it can be seen that a tube with t=200µm and d=1mm, due to the increased actual skin depth, should have less than 50% of the impedance increase than a solid d=1mm wire (do note that the curves are normalized w.r.t $ F / R_{dc} $, so interpretation is a bit tricky).
Similar effects (although not as dramatic) can be observed with individually-insulated stranded wire.
Application
In medium-frequency applications, as for example switching power supplies, it is common to use Litz Wire a multi-stranded insulated wire which reduces the losses due to skin effect but becomes less and less effective at higher frequencies (~1MHz) because of the proximity effect and the capacitive coupling of the individual strands.
Probably more gains (particularly with respect to proximity effects) could be obtained if there were multiple individual strands embedded around the periphery of a non-conducting core.
Question
Have I missed something in the theory?
If not, why isn't insulated core wire (either tubes or strands around a core) being commercially exploited for high-frequency inductor applications?
Addendum
As John Birckhead answer points out, flat wire has basically the same advantages with none of the disadvantages (e.g., fill factor). But this leads me to ask:
Why isn't insulated-core flat wire being used for these applications? It should have the same advantage of flat wire with nearly half the resistance at high enough frequencies. Are the possible gains inconsequential?
inductor high-frequency skin-effect litz-wire
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
$endgroup$
add a comment |
$begingroup$
Background
The commonly known skin effect formulas are derived and only apply to solid conductors. The commonly used "skin depth" only applies in these cases. It is for this reason that in some applications tubes are used, as these are much more weight-efficient than the same diameter wire at a high-enough frequency.
At 1MHz the skin depth of copper wire is 65µm which means that only 40% of the volume of a 1mm diameter wire is carrying 95% of the current, with >35% of it in the outside 20%.
From the skin-depth formulas it is known that a lower conductivity material (e.g., aluminum) has a skin depth that is considerably larger than a higher conductivity one (e.g., copper). As the formula predicts, skin depth is inversely proportional to the square root of the conductivity. If we carry this to its logical consequences, it should be the case that for a conducting tube (which has an insulation core) skin depth should be larger than for an equivalent solid conductor.
As an alternative intuition a thin-walled insulated-core conductor would have nearly twice the surface area of a solid conductor. So it should asymptotically approach nearly half the resistance at a high enough frequency.
In effect, as can be seen in this paper from HB Dwight in 1922 (possible paywall), the increase in resistance w.r.t. frequency for a tube whose wall thickness is 20% of its diameter is more than a factor of two lower than for a solid wire.
From the above curves it can be seen that a tube with t=200µm and d=1mm, due to the increased actual skin depth, should have less than 50% of the impedance increase than a solid d=1mm wire (do note that the curves are normalized w.r.t $ F / R_{dc} $, so interpretation is a bit tricky).
Similar effects (although not as dramatic) can be observed with individually-insulated stranded wire.
Application
In medium-frequency applications, as for example switching power supplies, it is common to use Litz Wire a multi-stranded insulated wire which reduces the losses due to skin effect but becomes less and less effective at higher frequencies (~1MHz) because of the proximity effect and the capacitive coupling of the individual strands.
Probably more gains (particularly with respect to proximity effects) could be obtained if there were multiple individual strands embedded around the periphery of a non-conducting core.
Question
Have I missed something in the theory?
If not, why isn't insulated core wire (either tubes or strands around a core) being commercially exploited for high-frequency inductor applications?
Addendum
As John Birckhead answer points out, flat wire has basically the same advantages with none of the disadvantages (e.g., fill factor). But this leads me to ask:
Why isn't insulated-core flat wire being used for these applications? It should have the same advantage of flat wire with nearly half the resistance at high enough frequencies. Are the possible gains inconsequential?
inductor high-frequency skin-effect litz-wire
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
$endgroup$
1
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat. Any conclusions reached should be edited back into the question and/or any answer(s).
$endgroup$
– Dave Tweed♦
11 hours ago
1
$begingroup$
I'll need to read it further, but I found this set of pages on Litz wire. Just a note.
$endgroup$
– jonk
10 hours ago
add a comment |
$begingroup$
Background
The commonly known skin effect formulas are derived and only apply to solid conductors. The commonly used "skin depth" only applies in these cases. It is for this reason that in some applications tubes are used, as these are much more weight-efficient than the same diameter wire at a high-enough frequency.
At 1MHz the skin depth of copper wire is 65µm which means that only 40% of the volume of a 1mm diameter wire is carrying 95% of the current, with >35% of it in the outside 20%.
From the skin-depth formulas it is known that a lower conductivity material (e.g., aluminum) has a skin depth that is considerably larger than a higher conductivity one (e.g., copper). As the formula predicts, skin depth is inversely proportional to the square root of the conductivity. If we carry this to its logical consequences, it should be the case that for a conducting tube (which has an insulation core) skin depth should be larger than for an equivalent solid conductor.
As an alternative intuition a thin-walled insulated-core conductor would have nearly twice the surface area of a solid conductor. So it should asymptotically approach nearly half the resistance at a high enough frequency.
In effect, as can be seen in this paper from HB Dwight in 1922 (possible paywall), the increase in resistance w.r.t. frequency for a tube whose wall thickness is 20% of its diameter is more than a factor of two lower than for a solid wire.
From the above curves it can be seen that a tube with t=200µm and d=1mm, due to the increased actual skin depth, should have less than 50% of the impedance increase than a solid d=1mm wire (do note that the curves are normalized w.r.t $ F / R_{dc} $, so interpretation is a bit tricky).
Similar effects (although not as dramatic) can be observed with individually-insulated stranded wire.
Application
In medium-frequency applications, as for example switching power supplies, it is common to use Litz Wire a multi-stranded insulated wire which reduces the losses due to skin effect but becomes less and less effective at higher frequencies (~1MHz) because of the proximity effect and the capacitive coupling of the individual strands.
Probably more gains (particularly with respect to proximity effects) could be obtained if there were multiple individual strands embedded around the periphery of a non-conducting core.
Question
Have I missed something in the theory?
If not, why isn't insulated core wire (either tubes or strands around a core) being commercially exploited for high-frequency inductor applications?
Addendum
As John Birckhead answer points out, flat wire has basically the same advantages with none of the disadvantages (e.g., fill factor). But this leads me to ask:
Why isn't insulated-core flat wire being used for these applications? It should have the same advantage of flat wire with nearly half the resistance at high enough frequencies. Are the possible gains inconsequential?
inductor high-frequency skin-effect litz-wire
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
$endgroup$
Background
The commonly known skin effect formulas are derived and only apply to solid conductors. The commonly used "skin depth" only applies in these cases. It is for this reason that in some applications tubes are used, as these are much more weight-efficient than the same diameter wire at a high-enough frequency.
At 1MHz the skin depth of copper wire is 65µm which means that only 40% of the volume of a 1mm diameter wire is carrying 95% of the current, with >35% of it in the outside 20%.
From the skin-depth formulas it is known that a lower conductivity material (e.g., aluminum) has a skin depth that is considerably larger than a higher conductivity one (e.g., copper). As the formula predicts, skin depth is inversely proportional to the square root of the conductivity. If we carry this to its logical consequences, it should be the case that for a conducting tube (which has an insulation core) skin depth should be larger than for an equivalent solid conductor.
As an alternative intuition a thin-walled insulated-core conductor would have nearly twice the surface area of a solid conductor. So it should asymptotically approach nearly half the resistance at a high enough frequency.
In effect, as can be seen in this paper from HB Dwight in 1922 (possible paywall), the increase in resistance w.r.t. frequency for a tube whose wall thickness is 20% of its diameter is more than a factor of two lower than for a solid wire.
From the above curves it can be seen that a tube with t=200µm and d=1mm, due to the increased actual skin depth, should have less than 50% of the impedance increase than a solid d=1mm wire (do note that the curves are normalized w.r.t $ F / R_{dc} $, so interpretation is a bit tricky).
Similar effects (although not as dramatic) can be observed with individually-insulated stranded wire.
Application
In medium-frequency applications, as for example switching power supplies, it is common to use Litz Wire a multi-stranded insulated wire which reduces the losses due to skin effect but becomes less and less effective at higher frequencies (~1MHz) because of the proximity effect and the capacitive coupling of the individual strands.
Probably more gains (particularly with respect to proximity effects) could be obtained if there were multiple individual strands embedded around the periphery of a non-conducting core.
Question
Have I missed something in the theory?
If not, why isn't insulated core wire (either tubes or strands around a core) being commercially exploited for high-frequency inductor applications?
Addendum
As John Birckhead answer points out, flat wire has basically the same advantages with none of the disadvantages (e.g., fill factor). But this leads me to ask:
Why isn't insulated-core flat wire being used for these applications? It should have the same advantage of flat wire with nearly half the resistance at high enough frequencies. Are the possible gains inconsequential?
inductor high-frequency skin-effect litz-wire
inductor high-frequency skin-effect litz-wire
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
edited 9 hours ago
Edgar Brown
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
asked 11 hours ago
Edgar BrownEdgar Brown
5,6872731
5,6872731
1
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat. Any conclusions reached should be edited back into the question and/or any answer(s).
$endgroup$
– Dave Tweed♦
11 hours ago
1
$begingroup$
I'll need to read it further, but I found this set of pages on Litz wire. Just a note.
$endgroup$
– jonk
10 hours ago
add a comment |
1
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat. Any conclusions reached should be edited back into the question and/or any answer(s).
$endgroup$
– Dave Tweed♦
11 hours ago
1
$begingroup$
I'll need to read it further, but I found this set of pages on Litz wire. Just a note.
$endgroup$
– jonk
10 hours ago
1
1
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat. Any conclusions reached should be edited back into the question and/or any answer(s).
$endgroup$
– Dave Tweed♦
11 hours ago
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat. Any conclusions reached should be edited back into the question and/or any answer(s).
$endgroup$
– Dave Tweed♦
11 hours ago
1
1
$begingroup$
I'll need to read it further, but I found this set of pages on Litz wire. Just a note.
$endgroup$
– jonk
10 hours ago
$begingroup$
I'll need to read it further, but I found this set of pages on Litz wire. Just a note.
$endgroup$
– jonk
10 hours ago
add a comment |
4 Answers
4
active
oldest
votes
$begingroup$
No, you are correct in the theory, but your approach leads to an unnecessary increase in volume when compared to using flat wire, which is both easier to manufacture and provides a similar advantage for skin effect and the advantage of volumetric efficiency.
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
$endgroup$
1
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
1
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
2
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
1
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
3
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
|
show 2 more comments
$begingroup$
Induction Heating (Industrial) commonly uses hollow copper tubing for the inductor.
When you are running 1000 kW or higher, you better believe the copper loss needs to be minimized.
Additionally, the hollow core is used for water cooling.
Sometimes the copper is called "hollow bar". It comes in rectangular or round. It is not uncommon to order a "mill run" to get the hollow bar and thickness desired.
Image from luvata dot com
answered 8 hours ago
MarlaMarla
3,91311226
$endgroup$
1
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
1
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
add a comment |
$begingroup$
Wikipedia entry for Litz wire contains a direct answer your question of "Why aren't hollow tubes used instead?":
One technique to reduce the resistance is to place more of the
conductive material near the surface where the current is by
replacing the wire with a hollow copper tube. The larger surface area
of the tube conducts the current with much less resistance than a
solid wire with the same cross-sectional area would. The tank coils of
high power radio transmitters are often made of copper tubing, silver
plated on the outside, to reduce resistance. However tubing is not
flexible and requires special tools to bend and shape.
The article goes on to describe why Litz wire provides an alternate solution.
answered 5 hours ago
JS.JS.
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
There is indeed a variant on insulated core wire for very high frequency applications. It's called a waveguide. It's a hollow tube used for conducting RF. I am of the understanding that the signal travels in the inside of the conducting shell rather than the outside, but the idea of only needing the conducting shell as thick as the skin effect dictates is there.
Not much use for inductors though.
answered 9 hours ago
elchambroelchambro
1092
$endgroup$
5
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
No, you are correct in the theory, but your approach leads to an unnecessary increase in volume when compared to using flat wire, which is both easier to manufacture and provides a similar advantage for skin effect and the advantage of volumetric efficiency.
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
$endgroup$
1
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
1
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
2
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
1
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
3
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
|
show 2 more comments
$begingroup$
No, you are correct in the theory, but your approach leads to an unnecessary increase in volume when compared to using flat wire, which is both easier to manufacture and provides a similar advantage for skin effect and the advantage of volumetric efficiency.
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
$endgroup$
1
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
1
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
2
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
1
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
3
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
|
show 2 more comments
$begingroup$
No, you are correct in the theory, but your approach leads to an unnecessary increase in volume when compared to using flat wire, which is both easier to manufacture and provides a similar advantage for skin effect and the advantage of volumetric efficiency.
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
$endgroup$
No, you are correct in the theory, but your approach leads to an unnecessary increase in volume when compared to using flat wire, which is both easier to manufacture and provides a similar advantage for skin effect and the advantage of volumetric efficiency.
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
answered 11 hours ago
John BirckheadJohn Birckhead
4,761416
4,761416
1
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
1
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
2
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
1
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
3
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
|
show 2 more comments
1
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
1
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
2
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
1
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
3
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
1
1
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
$begingroup$
I have never seen flat wire being used in RF applications, transformers, or inductors while Litz wire is quite common. Could you expand your answer to point to those and how it compares?
$endgroup$
– Edgar Brown
10 hours ago
1
1
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
$begingroup$
See mouser.com/pdfdocs/bourns_ic046_flatwire_inductor_appnote.pdf
$endgroup$
– John Birckhead
10 hours ago
2
2
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
$begingroup$
To your question, Litz wire also has poor volumetric efficiency for high-current applications because of the insulation and the way the wires cross each other in the coil. It is also difficult to terminate at high currents to get an even current distribution. It is useful at low currents when you are not space constrained, because flat wire is tricky to wind.
$endgroup$
– John Birckhead
10 hours ago
1
1
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
$begingroup$
If my intuition is correct, a flat wire with a non-conductive core would have less impedance at higher frequencies than a flat wire (and it should be relatively easy to construct by flattening a thin insulation-filled tube). So, although this points in the right direction and does answer the main aspect of the question, it does not fully address it. Are the gains insignificant, or the application space non-existent?
$endgroup$
– Edgar Brown
9 hours ago
3
3
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
$begingroup$
First of all, thanks for a really interesting and well-stated question, (near to my heart being a magnetics guy). It's just easier flattening the wire down to the skin depth - there would only be a marginal difference because there is insulation between two layers just as there would be insulation in your scenario in the center of the proposed conductor, and you can get the same cross section with a wider flat wire. It would be an interesting study to determine how much if any advantage is gained - it does "feel" like inter-winding capacitance might be less.
$endgroup$
– John Birckhead
9 hours ago
|
show 2 more comments
$begingroup$
Induction Heating (Industrial) commonly uses hollow copper tubing for the inductor.
When you are running 1000 kW or higher, you better believe the copper loss needs to be minimized.
Additionally, the hollow core is used for water cooling.
Sometimes the copper is called "hollow bar". It comes in rectangular or round. It is not uncommon to order a "mill run" to get the hollow bar and thickness desired.
Image from luvata dot com
answered 8 hours ago
MarlaMarla
3,91311226
$endgroup$
1
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
1
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
add a comment |
$begingroup$
Induction Heating (Industrial) commonly uses hollow copper tubing for the inductor.
When you are running 1000 kW or higher, you better believe the copper loss needs to be minimized.
Additionally, the hollow core is used for water cooling.
Sometimes the copper is called "hollow bar". It comes in rectangular or round. It is not uncommon to order a "mill run" to get the hollow bar and thickness desired.
Image from luvata dot com
answered 8 hours ago
MarlaMarla
3,91311226
$endgroup$
1
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
1
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
add a comment |
$begingroup$
Induction Heating (Industrial) commonly uses hollow copper tubing for the inductor.
When you are running 1000 kW or higher, you better believe the copper loss needs to be minimized.
Additionally, the hollow core is used for water cooling.
Sometimes the copper is called "hollow bar". It comes in rectangular or round. It is not uncommon to order a "mill run" to get the hollow bar and thickness desired.
Image from luvata dot com
answered 8 hours ago
MarlaMarla
3,91311226
$endgroup$
Induction Heating (Industrial) commonly uses hollow copper tubing for the inductor.
When you are running 1000 kW or higher, you better believe the copper loss needs to be minimized.
Additionally, the hollow core is used for water cooling.
Sometimes the copper is called "hollow bar". It comes in rectangular or round. It is not uncommon to order a "mill run" to get the hollow bar and thickness desired.
Image from luvata dot com
answered 8 hours ago
MarlaMarla
3,91311226
edited 6 hours ago
answered 8 hours ago
MarlaMarla
3,91311226
answered 8 hours ago
MarlaMarla
3,91311226
answered 8 hours ago
MarlaMarla
3,91311226
3,91311226
1
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
1
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
add a comment |
1
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
1
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
1
1
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
$begingroup$
At what frequency is this normally operating?
$endgroup$
– Edgar Brown
7 hours ago
1
1
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
$begingroup$
@EdgarBrown . .Induction heaters are used from 50 Hz to several megahertz. Mostly below 50 kHz though.
$endgroup$
– Marla
6 hours ago
add a comment |
$begingroup$
Wikipedia entry for Litz wire contains a direct answer your question of "Why aren't hollow tubes used instead?":
One technique to reduce the resistance is to place more of the
conductive material near the surface where the current is by
replacing the wire with a hollow copper tube. The larger surface area
of the tube conducts the current with much less resistance than a
solid wire with the same cross-sectional area would. The tank coils of
high power radio transmitters are often made of copper tubing, silver
plated on the outside, to reduce resistance. However tubing is not
flexible and requires special tools to bend and shape.
The article goes on to describe why Litz wire provides an alternate solution.
answered 5 hours ago
JS.JS.
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
Wikipedia entry for Litz wire contains a direct answer your question of "Why aren't hollow tubes used instead?":
One technique to reduce the resistance is to place more of the
conductive material near the surface where the current is by
replacing the wire with a hollow copper tube. The larger surface area
of the tube conducts the current with much less resistance than a
solid wire with the same cross-sectional area would. The tank coils of
high power radio transmitters are often made of copper tubing, silver
plated on the outside, to reduce resistance. However tubing is not
flexible and requires special tools to bend and shape.
The article goes on to describe why Litz wire provides an alternate solution.
answered 5 hours ago
JS.JS.
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
Wikipedia entry for Litz wire contains a direct answer your question of "Why aren't hollow tubes used instead?":
One technique to reduce the resistance is to place more of the
conductive material near the surface where the current is by
replacing the wire with a hollow copper tube. The larger surface area
of the tube conducts the current with much less resistance than a
solid wire with the same cross-sectional area would. The tank coils of
high power radio transmitters are often made of copper tubing, silver
plated on the outside, to reduce resistance. However tubing is not
flexible and requires special tools to bend and shape.
The article goes on to describe why Litz wire provides an alternate solution.
answered 5 hours ago
JS.JS.
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
Wikipedia entry for Litz wire contains a direct answer your question of "Why aren't hollow tubes used instead?":
One technique to reduce the resistance is to place more of the
conductive material near the surface where the current is by
replacing the wire with a hollow copper tube. The larger surface area
of the tube conducts the current with much less resistance than a
solid wire with the same cross-sectional area would. The tank coils of
high power radio transmitters are often made of copper tubing, silver
plated on the outside, to reduce resistance. However tubing is not
flexible and requires special tools to bend and shape.
The article goes on to describe why Litz wire provides an alternate solution.
answered 5 hours ago
JS.JS.
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 5 hours ago
JS.JS.
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 5 hours ago
JS.JS.
1313
answered 5 hours ago
JS.JS.
1313
1313
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
JS. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
$begingroup$
There is indeed a variant on insulated core wire for very high frequency applications. It's called a waveguide. It's a hollow tube used for conducting RF. I am of the understanding that the signal travels in the inside of the conducting shell rather than the outside, but the idea of only needing the conducting shell as thick as the skin effect dictates is there.
Not much use for inductors though.
answered 9 hours ago
elchambroelchambro
1092
$endgroup$
5
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
add a comment |
$begingroup$
There is indeed a variant on insulated core wire for very high frequency applications. It's called a waveguide. It's a hollow tube used for conducting RF. I am of the understanding that the signal travels in the inside of the conducting shell rather than the outside, but the idea of only needing the conducting shell as thick as the skin effect dictates is there.
Not much use for inductors though.
answered 9 hours ago
elchambroelchambro
1092
$endgroup$
5
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
add a comment |
$begingroup$
There is indeed a variant on insulated core wire for very high frequency applications. It's called a waveguide. It's a hollow tube used for conducting RF. I am of the understanding that the signal travels in the inside of the conducting shell rather than the outside, but the idea of only needing the conducting shell as thick as the skin effect dictates is there.
Not much use for inductors though.
answered 9 hours ago
elchambroelchambro
1092
$endgroup$
There is indeed a variant on insulated core wire for very high frequency applications. It's called a waveguide. It's a hollow tube used for conducting RF. I am of the understanding that the signal travels in the inside of the conducting shell rather than the outside, but the idea of only needing the conducting shell as thick as the skin effect dictates is there.
Not much use for inductors though.
answered 9 hours ago
elchambroelchambro
1092
answered 9 hours ago
elchambroelchambro
1092
answered 9 hours ago
elchambroelchambro
1092
answered 9 hours ago
elchambroelchambro
1092
1092
5
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
add a comment |
5
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
5
5
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
$begingroup$
A waveguide is a rather different thing. The RF is travelling in the air itself, and being "reflected" off the inside (to simplify), rather than actually travelling in the metal of the waveguide itself,
$endgroup$
– mbrig
7 hours ago
add a comment |
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Comments are not for extended discussion; this conversation has been moved to chat. Any conclusions reached should be edited back into the question and/or any answer(s).
$endgroup$
– Dave Tweed♦
11 hours ago
1
$begingroup$
I'll need to read it further, but I found this set of pages on Litz wire. Just a note.
$endgroup$
– jonk
10 hours ago