Interesting set of papers

[godigit1]

Ive been trying to learn and see if I can find any advantages in using flat wire in spiral coils.
Of coarse there is not much out there that is P.I specific.

http://g3rbj.co.uk/

This set of articles particularly the one on skin effect proxomity effect and the resistance of circular and round conductors has kinda changed the way Im looking at things. And like I said Im trying to learn.

So I have a question as far as air gap.
In a Pi coil we have been designing Ideally with a high dialectric thick insulation between wraps in order to reduce capacitance.
In a transformer they are designed to use all available surface area, The more spacing in or between transformer windings increases the capacitance .

A coil is a transformer or at least a DD is so can anyone help to explain the differance in relationships as pertaining to Pi coils?

Thanks

[green]

Ive been trying to learn and see if I can find any advantages in using flat wire in spiral coils.
Of coarse there is not much out there that is P.I specific.

http://g3rbj.co.uk/

This set of articles particularly the one on skin effect proxomity effect and the resistance of circular and round conductors has kinda changed the way Im looking at things. And like I said Im trying to learn.

So I have a question as far as air gap.
In a Pi coil we have been designing Ideally with a high dialectric thick insulation between wraps in order to reduce capacitance.
In a transformer they are designed to use all available surface area, The more spacing in or between transformer windings increases the capacitance .

A coil is a transformer or at least a DD is so can anyone help to explain the differance in relationships as pertaining to Pi coils?

Thanks

I'm trying to learn also so probably can't help much. Was surprised to see effect of broken or not soldered wires(2.8. Effect of Broken Strands) in: Litz for HF Single Layer Coils. Think I remember reading in one of the threads not to long ago that a broken or not soldered strand is a major problem. Maybe it is with a PI coil?

[godigit1]

I'm trying to learn also so probably can't help much. Was surprised to see effect of broken or not soldered wires(2.8. Effect of Broken Strands) in: Litz for HF Single Layer Coils. Think I remember reading in one of the threads not to long ago that a broken or not soldered strand is a major problem. Maybe it is with a PI coil?

How I understand it the broken wire could cause a mirroring effect. Like you would see in a non terminated transmission line or with not properly matched impediances.
Depending on where it is, at a solder joint at the tx or rx side or in the middle of the coil I would think causes different behaviors but Ive done no tests to validate this assumption.
Also thinking doesnt matter the noise will be throughout the coil the broken wire would act like a transformer or a capacitor within the coil.
Does that sound right?

[dbanner]

Transformers exhibit "distributive capacitances"
Firstly, the capacitances that exists between the two ends of a given winding. Secondly, between adjacent windings, and thirdly, between the windings and the core.
The first one, namely the capacitances between the ends of the windings, is known as "shunt" capacitance, and is affected by the presence of a core and the insulation between the windings and the core, (dialectric constant of insulation).
In the absence of a core(air core), we are left with inter wire capacitance as the more important consideration having effect on shunt capacitance.
Of course the shield also imparts capacitative effects and is entirely empirical to any equations derived.

[dbanner]

Now in a typical transformer, the distributive capacitance varies directly(directly proportional) to the width of the winding layer. The effect of increased distance between the windings increases the overall width of the winding and increases capacitance because of the presence of the CORE( distributive capacitance between the windings and the core). This is entirely different from inter wire capacitance.

[dbanner]

The winding geometry of the spiral coil offers the optimum means of reducing capacitance between windings since each successive turn is further out from the first turn. At least in theory

[godigit1]

Transformers exhibit "distributive capacitances"
Firstly, the capacitances that exists between the two ends of a given winding. Secondly, between adjacent windings, and thirdly, between the windings and the core.
The first one, namely the capacitances between the ends of the windings, is known as "shunt" capacitance, and is affected by the presence of a core and the insulation between the windings and the core, (dialectric constant of insulation).
In the absence of a core(air core), we are left with inter wire capacitance as the more important consideration having effect on shunt capacitance.
Of course the shield also imparts capacitative effects and is entirely empirical to any equations derived.

Hi dbanner,
Thank you for your response.
Im been tyring to teach myself advanced math, physics, electronics and what im calling wire dynamics. Its been a adventure to say the least.
Most of what im finding seems contrairy to what ive learned here on the forum about coils.
For example dialectric constant of insulation.
In this paper a lesser dialectric constant is preferable to increase Q in the coil.
http://g3rbj.co.uk/wp-content/upload...e-a-coil-4.pdf.

I know its probably my lack of complete understanding of the dynamics involved so i will continue to studyup.

My intent is to design a wire "Litz" thats more suitable to a Pi coil.
with everything im researching im thinking 4 to six wires only in the 30 to 36 awg range and adjusting the # of twists to a optimal resistance for fast charging of the coil.
Been thinking about twisted pairs left and right but this would in my understanding increase capacitance in the wire. the wire would no longer lay into each other properly.

Ive been building a wire twister that will be capable of a max of 40 twists per inch.
This is a little extreme maybe but i wanted to experiment with a twist such as this maybe.

Sorry for the huge image

[godigit1]

image dissapered

[bbsailor]

Hi dbanner,
Thank you for your response.
Im been tyring to teach myself advanced math, physics, electronics and what im calling wire dynamics. Its been a adventure to say the least.
Most of what im finding seems contrairy to what ive learned here on the forum about coils.
For example dialectric constant of insulation.
In this paper a lesser dialectric constant is preferable to increase Q in the coil.
http://g3rbj.co.uk/wp-content/upload...e-a-coil-4.pdf.

I know its probably my lack of complete understanding of the dynamics involved so i will continue to studyup.

My intent is to design a wire "Litz" thats more suitable to a Pi coil.
with everything im researching im thinking 4 to six wires only in the 30 to 36 awg range and adjusting the # of twists to a optimal resistance for fast charging of the coil.
Been thinking about twisted pairs left and right but this would in my understanding increase capacitance in the wire. the wire would no longer lay into each other properly.

Ive been building a wire twister that will be capable of a max of 40 twists per inch.
This is a little extreme maybe but i wanted to experiment with a twist such as this maybe.

Sorry for the huge image

godigit1,

Any thing within the coil electrostatic field, closer to the coil with more effect and higher dielectric with more effect will have an effect on the coil self resonance by lowering it. Try to use a very low capacitance probe to see the effect as it could be as small as a few hundred to one thousand Hz. Bottom line: lower dielectric constants of coil wire insulation, spiral wrap to hold the coil together, coil to shield spacers and coil core or bobbin materiel will produce a higher self resonant coil reflecting less capacitance than using stuff with a higher dielectric constant.

Litz wire allows the higher harmonics of the coil sharp edge square waves and other quick changing waveforms to maintain their sharp edge and not appear as more rounded edges. To effectively use Litz wire, each strand on both the start and end of the coil winding needs to be connected in the solder connection to ensure that current is flowing in each strand of the Litz wire to get the maximum benefit of using this type wire. Try to use an individual strand size small enough to not be seen as a target at your lowest delay. I find that I can use AWG 30 strands down to about 7 us.

Joseph J. Rogowski

[green]

godigit1,

Any thing within the coil electrostatic field, closer to the coil with more effect and higher dielectric with more effect will have an effect on the coil self resonance by lowering it. Try to use a very low capacitance probe to see the effect as it could be as small as a few hundred to one thousand Hz. Bottom line: lower dielectric constants of coil wire insulation, spiral wrap to hold the coil together, coil to shield spacers and coil core or bobbin materiel will produce a higher self resonant coil reflecting less capacitance than using stuff with a higher dielectric constant.

Litz wire allows the higher harmonics of the coil sharp edge square waves and other quick changing waveforms to maintain their sharp edge and not appear as more rounded edges. To effectively use Litz wire, each strand on both the start and end of the coil winding needs to be connected in the solder connection to ensure that current is flowing in each strand of the Litz wire to get the maximum benefit of using this type wire. Try to use an individual strand size small enough to not be seen as a target at your lowest delay. I find that I can use AWG 30 strands down to about 7 us.

Joseph J. Rogowski

AWG30 wire has a .19us TC. 7us would be over 30TC's. Are you thinking the wire is seen as a target out close to 7us or is something else limiting the delay to 7us?

[bbsailor]

AWG30 wire has a .19us TC. 7us would be over 30TC's. Are you thinking the wire is seen as a target out close to 7us or is something else limiting the delay to 7us?

Green,

If the mono coil PI circuit had the potential to go below about 7 us, I am sure that the AWG 30 could go down to about 5 us delay or less. There are other things that come into the situation. Remember, it is not just the wire. It is the whole coil with a shield, connection to the coax wire, the circuit balance, and the damping resistor value that all tend to increase the minimum delay value above just the wire reaction.

At very low delays circuit speed becomes more important as well as these things.
1. Preamp gain.
2. Time to come out of saturation
3. TX current
4. Coil Wire eddy current retention
5. Any interaction within the coil at low delays that are not seen at higher delays.
6. Damping resistor value
7. Circuit drift from optimum values and balancing

Joseph J. Rogowski

[ivconic]

It is always good to get four for a price of one.
400% discount!

[bbsailor]

It is always good to get four for a price of one.
400% discount!

Some kind of software problem caused this. I only intended to make one post on my Apple Air 2 tablet.

Moderators, please delete the duplicates!!!

Thanks

Joseph J. Rogowski

[Qiaozhi]

Some kind of software problem caused this. I only intended to make one post on my Apple Air 2 tablet.

Moderators, please delete the duplicates!!!

Thanks

Joseph J. Rogowski

Done!

[godigit1]

godigit1,

Any thing within the coil electrostatic field, closer to the coil with more effect and higher dielectric with more effect will have an effect on the coil self resonance by lowering it. Try to use a very low capacitance probe to see the effect as it could be as small as a few hundred to one thousand Hz. Bottom line: lower dielectric constants of coil wire insulation, spiral wrap to hold the coil together, coil to shield spacers and coil core or bobbin materiel will produce a higher self resonant coil reflecting less capacitance than using stuff with a higher dielectric constant.

Litz wire allows the higher harmonics of the coil sharp edge square waves and other quick changing waveforms to maintain their sharp edge and not appear as more rounded edges. To effectively use Litz wire, each strand on both the start and end of the coil winding needs to be connected in the solder connection to ensure that current is flowing in each strand of the Litz wire to get the maximum benefit of using this type wire. Try to use an individual strand size small enough to not be seen as a target at your lowest delay. I find that I can use AWG 30 strands down to about 7 us.

Joseph J. Rogowski

Thank you Joseph for your response Ive been reading so much I had a dyslexic moment, confused the relation of dialectric and resistance was thinking high dialectric high resistance, I know better.

As far as litz

Do you think 6 strands of 32 (24 awg equivalent) guage magnet wire will be sufficient to maintain the integrity of the squarewaveform ?
32 awg wire is good to about 15k should be good for a Pi at 2500 pps or less as far as skin effect goes.
My thinking behind minimalizing strands and increasing strand size is to maintain a small bundle size and try to get full penetration of skin throughout the bundle.

Also by using bigger strands each strand has less resistance giving me more room to play with twist and lay.
Any resistance benefit from litz comes mostly from the first two strands and falls exponentially from there.

Have you played with twisted pairs in coil construction?

Is there any benefit to left and right twisted pairs in litz wire? could this cancel out signals as well as emi efi ?

I have found no litz that is sold left and right hand twisted it is kinda contrary to the way litz is made as it disrupts to lay of the wire creating air gaps. The litz Ive looked at so far is all twisted right hand.
No doubt there is some custom special made litz twisted this way but I cannot find it.

The more I research the more I am starting to think opposing twisted pairs within the coil itself may cancel out small signals.

Thanks again for all the help and knowledge you impart to the members of this forum.