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More inductor talk, Proximity effect, self capacitance

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  More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-28 13:42 -0500
    Re: More inductor talk, Proximity effect, self capacitance boB <boB@theresnoplacelikehome.com> - 2016-09-28 14:08 -0700
      Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-28 17:06 -0500
        Re: More inductor talk, Proximity effect, self capacitance "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-09-28 23:50 -0500
          Re: More inductor talk, Proximity effect, self capacitance boB <boB@theresnoplacelikehome.com> - 2016-09-28 22:27 -0700
        Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-10-03 15:46 -0500
    Re: More inductor talk, Proximity effect, self capacitance Winfield Hill <hill@rowland.harvard.edu> - 2016-09-28 15:38 -0700
      Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-28 19:16 -0500
      Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-28 22:06 -0500
        Re: More inductor talk, Proximity effect, self capacitance Winfield Hill <hill@rowland.harvard.edu> - 2016-09-28 20:17 -0700
          Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-29 06:13 -0500
            Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-29 08:29 -0500
              Re: More inductor talk, Proximity effect, self capacitance Winfield Hill <hill@rowland.harvard.edu> - 2016-09-29 06:54 -0700
                Re: More inductor talk, Proximity effect, self capacitance boB <boB@theresnoplacelikehome.com> - 2016-09-29 11:57 -0700
                  Re: More inductor talk, Proximity effect, self capacitance Winfield Hill <hill@rowland.harvard.edu> - 2016-09-29 12:29 -0700
    Re: More inductor talk, Proximity effect, self capacitance George Herold <gherold@teachspin.com> - 2016-09-29 06:55 -0700
      Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-29 10:59 -0500
        Re: More inductor talk, Proximity effect, self capacitance makolber@yahoo.com - 2016-09-29 09:15 -0700
          Re: More inductor talk, Proximity effect, self capacitance amdx <nojunk@knology.net> - 2016-09-29 13:16 -0500

#429681 — More inductor talk, Proximity effect, self capacitance

A fine gentleman did an experiment building two inductors.
The coils were wound with 420/46 litz. Both inductors have 40 turns.
One inductor is close wound (215uh 7.7pf distributed capacitance).
The second has a 0.625/wire diameter space between wires, (187uh and 6.9 
pf distributed capacitance).
   The inductor with spacing has a higher Q, except at the low end

where the Q's are equal.

The reason for spacing the wire is to reduce Proximity effect.


Here is the graph, each coil was tested twice (two lines each)



> http://s395.photobucket.com/user/Qmavam/media/Close%20vs%20space%20wound._zpsctlfmjdi.png.html


What would be the reason that the Q does not start out higher,
but moves up with frequency?



                                      Mikek

Re: the difference in inductance, both 40 turns.
The inductance,  215uh vs 187uh = 86.9%
The capacitance 7.7 vs 6.9 = 89.6%
The capacitance of 40 turns did go down 10.3% with spacing.
The inductance went down 13% with spacing.   FWIW

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#429706

On Wed, 28 Sep 2016 13:42:06 -0500, amdx <nojunk@knology.net> wrote:

>A fine gentleman did an experiment building two inductors.
>The coils were wound with 420/46 litz. Both inductors have 40 turns.
>One inductor is close wound (215uh 7.7pf distributed capacitance).
>The second has a 0.625/wire diameter space between wires, (187uh and 6.9 
>pf distributed capacitance).
>   The inductor with spacing has a higher Q, except at the low end
>
>where the Q's are equal.
>
>The reason for spacing the wire is to reduce Proximity effect.
>
>
>Here is the graph, each coil was tested twice (two lines each)
>
>
>
>> http://s395.photobucket.com/user/Qmavam/media/Close%20vs%20space%20wound._zpsctlfmjdi.png.html
>
>
>What would be the reason that the Q does not start out higher,
>but moves up with frequency?


Probably because of the the AC resistance....  The real part of the
impedance.

I don't see that figure displayed.

boB


>
>
>
>                                      Mikek
>
>Re: the difference in inductance, both 40 turns.
>The inductance,  215uh vs 187uh = 86.9%
>The capacitance 7.7 vs 6.9 = 89.6%
>The capacitance of 40 turns did go down 10.3% with spacing.
>The inductance went down 13% with spacing.   FWIW

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#429713

On 9/28/2016 4:08 PM, boB wrote:
> On Wed, 28 Sep 2016 13:42:06 -0500, amdx <nojunk@knology.net> wrote:
>
>> A fine gentleman did an experiment building two inductors.
>> The coils were wound with 420/46 litz. Both inductors have 40 turns.
>> One inductor is close wound (215uh 7.7pf distributed capacitance).
>> The second has a 0.625/wire diameter space between wires, (187uh and 6.9
>> pf distributed capacitance).
>>    The inductor with spacing has a higher Q, except at the low end
>>
>> where the Q's are equal.
>>
>> The reason for spacing the wire is to reduce Proximity effect.
>>
>>
>> Here is the graph, each coil was tested twice (two lines each)
>>
>>
>>
>>> http://s395.photobucket.com/user/Qmavam/media/Close%20vs%20space%20wound._zpsctlfmjdi.png.html
>>
>>
>> What would be the reason that the Q does not start out higher,
>> but moves up with frequency?
>
>
>
>
>>
>>
>>
>>                                       Mikek
>>
>> Re: the difference in inductance, both 40 turns.
>> The inductance,  215uh vs 187uh = 86.9%
>> The capacitance 7.7 vs 6.9 = 89.6%
>> The capacitance of 40 turns did go down 10.3% with spacing.
>> The inductance went down 13% with spacing.   FWIW



> Probably because of the the AC resistance....  The real part of the

> impedance.

>

> I don't see that figure displayed.

>

> boB

Try the figure again, it works for me.
> http://i395.photobucket.com/albums/pp37/Qmavam/Close%20vs%20space%20wound._zpsctlfmjdi.png


But note: the coils have near identical Q's and then the spaced coils Q
rises quickly, why didn't it just start out higher as it should have
less loss because of less proximity effect. That only shows up at higher 
frequencies, why?

                                 Mikek

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#429774

"amdx" <nojunk@knology.net> wrote in message 
news:nshesd$mim$1@dont-email.me...
> But note: the coils have near identical Q's and then the spaced coils Q
> rises quickly, why didn't it just start out higher as it should have
> less loss because of less proximity effect. That only shows up at higher 
> frequencies, why?

Assuming they were wound with equal lengths of wire (give or take a modest 
margin), and wound for the same inductances, then at low frequency, DCR is 
equal and inductance is equal.

At high frequencies, ACR rises for the close-spaced one, due to proximity 
effect, while the spaced one rises less.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#429777

On Wed, 28 Sep 2016 23:50:51 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"amdx" <nojunk@knology.net> wrote in message 
>news:nshesd$mim$1@dont-email.me...
>> But note: the coils have near identical Q's and then the spaced coils Q
>> rises quickly, why didn't it just start out higher as it should have
>> less loss because of less proximity effect. That only shows up at higher 
>> frequencies, why?
>
>Assuming they were wound with equal lengths of wire (give or take a modest 
>margin), and wound for the same inductances, then at low frequency, DCR is 
>equal and inductance is equal.


That's what I was kinda thinking...  So then, the low and similar
value of Q at low frequencies or near DC.

BTW, it was the resistance that I did not see listed...  The figure
came through fine of course.

>
>At high frequencies, ACR rises for the close-spaced one, due to proximity 
>effect, while the spaced one rises less.


This makes a lot of sense.  Less proximity... less proximity effect.


>
>Tim

boB

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#430226

On 9/28/2016 5:06 PM, amdx wrote:

>
> Try the figure again, it works for me.
>> http://i395.photobucket.com/albums/pp37/Qmavam/Close%20vs%20space%20wound._zpsctlfmjdi.png
>>
>
>
> But note: the coils have near identical Q's and then the spaced coils Q
> rises quickly, why didn't it just start out higher as it should have
> less loss because of less proximity effect. That only shows up at higher
> frequencies, why?
>
>                                 Mikek
>
>
  I think I found some ideas here.

> http://www.crystal-radio.eu/enlckring.htm

Where he says,

The Q factor of a unloaded LC circuit is determined by the following 
factors: series resistance in the circuit, parallel resistance across 
the circuit and magnetic losses.

The  series resistance in the LC circuit,
the lower the series resistance the higher the Q.

The total series resistance in the circuit (Rs) is the sum of:

The wire resistance of the coil, thicker wire or litzwire with much 
strands helps to reduce wire resistance.

The resistance of the capacitor plates, silvered plates gives the lowest 
resistance.
Plates with oxide gives more resistance than clean plates.

Contact resistance between rotor and frame of the variable capacitor, 
preferable the variable capacitor has a spring connected to rotor and 
frame, this provides a low resistance.
When the contact is made with a slidercontact at the rotor, this must be 
clean and free of oxide.



The parallel resistance across the LC circuit,
the higher the parallel resistance, the higher the Q.

Parallel resistance across the circuit (Rp) is caused by dielectric losses.

There are:
Dielectric losses in the coilformer
Dielectric losses in the insulation of the coilwire
Dielectric losses in the insulators of the tuning capacitor
Dielectric losses in materials placed near the coil or tuning capacitor, 
look  here for more information about this subject.
If the capacitor plates are not clean: dielectric losses in the dirt and 
oxide on the capacitor plates.

Also there can be a leaking resistance in insulators, e.g. by moisture.

All these losses together makes a parallel resistance (Rp) across the LC 
circuit.


Magnetic losses
This occurs when a magnetic material (iron) is placed near the coil.
Non magnetic materials (plastic, wood, aluminium etc.) don't give 
magnetic losses.

Why is the Q factor not constant for all frequencies?

The series resistance Rs gives a reduction of Q.
If we leave other losses out of consideration, the Q will have a value of:

Q= 2.pi.f.L / Rs

If the value of Rs is constant, the value of Q will increase with 
increasing frequency (f).
A series resistance in the circuit will especially give a reduction of Q 
at lower frequencies.

On the other hand:
if we only look at the losses caused by the parallel resistance Rp, the 
Q will have a value of:

Q=Rp / (2.pi.f.L)

Here we see, that at a constant value of Rp, the Q will decrease with 
increasing frequency (f).
A parallel resistance across the circuit will especially give a 
reduction of Q at higher frequencies.

The value of Q will both depend on series and parallel resistance, it is 
possible that a LC circuit gives a increasing Q at increasing frequency 
(because of series resistance) and than Q will reduce (because of the 
parallel resistance).
In this case we have a peak in Q somewhere in the frequency band.

Often the losses caused by the parallel resistance are the highest, and 
we only see a reduction of Q at higher frequencies in the medium wave band.
Than there is also a peak in Q, but this occurs at a frequency lower 
than we use.

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#429717

amdx wrote...
>
>A fine gentleman did an experiment building two inductors.
>The coils were wound with 420/46 litz. Both inductors have 40 turns.
>One inductor is close wound (215uh 7.7pf distributed capacitance).
>The second has a 0.625/wire diameter space between wires, (187uh and 6.9 
>pf distributed capacitance).
>   The inductor with spacing has a higher Q, except at the low end
>where the Q's are equal.

 What was the SRF for each coil?


-- 
 Thanks,
    - Win

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#429727

On 9/28/2016 5:38 PM, Winfield Hill wrote:
> amdx wrote...
>>
>> A fine gentleman did an experiment building two inductors.
>> The coils were wound with 420/46 litz. Both inductors have 40 turns.
>> One inductor is close wound (215uh 7.7pf distributed capacitance).
>> The second has a 0.625/wire diameter space between wires, (187uh and 6.9
>> pf distributed capacitance).
>>   The inductor with spacing has a higher Q, except at the low end
>> where the Q's are equal.
>
>  What was the SRF for each coil?
>
>

  I don't have that info.
I'll see if I can get it.
                     Mikek

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#429761

On 9/28/2016 5:38 PM, Winfield Hill wrote:
> amdx wrote...
>>
>> A fine gentleman did an experiment building two inductors.
>> The coils were wound with 420/46 litz. Both inductors have 40 turns.
>> One inductor is close wound (215uh 7.7pf distributed capacitance).
>> The second has a 0.625/wire diameter space between wires, (187uh and 6.9
>> pf distributed capacitance).
>>   The inductor with spacing has a higher Q, except at the low end
>> where the Q's are equal.
>
>  What was the SRF for each coil?
>
>

  The fine gentleman, who does good work sent back the following.

"I don’t have measured SRF’s.  Can’t be measured on a Q meter.
  But, you can calculate SRF’s from L (true value) and Co.

For these coils:

Closewound:  L = 214.8 uH; Co = 7.7 pF; SRF = 3.91 MHz

Spaced:  L = 187.2 uH; Co = 6.9 pF; SRF = 4.43 MHz."

                                      Mikek

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#429764

amdx wrote...
>
> Winfield Hill wrote:
>> amdx wrote...
>>>
>>> A fine gentleman did an experiment building two inductors.
>>
>>  What was the SRF for each coil?
>
> The fine gentleman, who does good work sent back the following.
> "I don’t have measured SRF’s.  Can’t be measured on a Q meter.
> But, you can calculate SRF’s from L (true value) and Co.
> For these coils:
> Closewound:  L = 214.8 uH; Co = 7.7 pF; SRF = 3.91 MHz
> Spaced:  L = 187.2 uH; Co = 6.9 pF; SRF = 4.43 MHz."

 A Q meter is not needed.  A common reason for measuring
 SRF is to see the measured capacitive parameter values.  


-- 
 Thanks,
    - Win

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#429787

On 9/28/2016 10:17 PM, Winfield Hill wrote:
> amdx wrote...
>>
>> Winfield Hill wrote:
>>> amdx wrote...
>>>>
>>>> A fine gentleman did an experiment building two inductors.
>>>
>>>  What was the SRF for each coil?
>>
>> The fine gentleman, who does good work sent back the following.
>> "I don’t have measured SRF’s.  Can’t be measured on a Q meter.
>> But, you can calculate SRF’s from L (true value) and Co.
>> For these coils:
>> Closewound:  L = 214.8 uH; Co = 7.7 pF; SRF = 3.91 MHz
>> Spaced:  L = 187.2 uH; Co = 6.9 pF; SRF = 4.43 MHz."
>
>  A Q meter is not needed.  A common reason for measuring
>  SRF is to see the measured capacitive parameter values.
>
>

  The fine gentleman must have calculated the capacitance.
A program often used to calculate it is here.

> http://electronbunker.ca/Extras/Downloads/LoopSelfCap_r1c.xls

The program uses The Least Squares Method.

                                              Mikek

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#429796

On 9/29/2016 6:13 AM, amdx wrote:
> On 9/28/2016 10:17 PM, Winfield Hill wrote:
>> amdx wrote...
>>>
>>> Winfield Hill wrote:
>>>> amdx wrote...
>>>>>
>>>>> A fine gentleman did an experiment building two inductors.
>>>>
>>>>  What was the SRF for each coil?
>>>
>>> The fine gentleman, who does good work sent back the following.
>>> "I don’t have measured SRF’s.  Can’t be measured on a Q meter.
>>> But, you can calculate SRF’s from L (true value) and Co.
>>> For these coils:
>>> Closewound:  L = 214.8 uH; Co = 7.7 pF; SRF = 3.91 MHz
>>> Spaced:  L = 187.2 uH; Co = 6.9 pF; SRF = 4.43 MHz."
>>
>>  A Q meter is not needed.  A common reason for measuring
>>  SRF is to see the measured capacitive parameter values.
>>
>>
>
>  The fine gentleman must have calculated the capacitance.
> A program often used to calculate it is here.
>
>> http://electronbunker.ca/Extras/Downloads/LoopSelfCap_r1c.xls
>
> The program uses The Least Squares Method.
>
>                                              Mikek
>

Here's paper,
The self-resonance and self-capacitance of solenoid coils:
> http://www.g3ynh.info/zdocs/magnetics/appendix/self_res/self-res.pdf

It's mostly over my head, has some neat pictures showing nodes with a 
mercury tube.
   Pages 39, 41, and 98 discuss self cap. page 77 is on SRF and page 101,
  is a summary.

                                      Mikek

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#429799

amdx wrote...
>
>>  The fine gentleman must have calculated the capacitance.

 It's a shame it wasn't measured.


-- 
 Thanks,
    - Win

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#429832

On 29 Sep 2016 06:54:08 -0700, Winfield Hill
<hill@rowland.harvard.edu> wrote:

>amdx wrote...
>>
>>>  The fine gentleman must have calculated the capacitance.
>
> It's a shame it wasn't measured.


This is why I love my old (refurbished)  HP-4194A impedance analyzer !

It's great for these kinds of measurements and finding resonant
frequencies, etc.

boB

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#429833

boB wrote...
>
> Winfield Hill wrote:
>> amdx wrote...
>>>
>>>>  The fine gentleman must have calculated the capacitance.
>>
>> It's a shame it wasn't measured.
>
>
>This is why I love my old (refurbished)  HP-4194A impedance analyzer !
>
>It's great for these kinds of measurements and finding resonant
>frequencies, etc.

Hear, hear!


-- 
 Thanks,
    - Win

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#429800

On Wednesday, September 28, 2016 at 2:42:14 PM UTC-4, amdx wrote:
> A fine gentleman did an experiment building two inductors.
> The coils were wound with 420/46 litz. Both inductors have 40 turns.
> One inductor is close wound (215uh 7.7pf distributed capacitance).
> The second has a 0.625/wire diameter space between wires, (187uh and 6.9 
> pf distributed capacitance).
>    The inductor with spacing has a higher Q, except at the low end
> 
> where the Q's are equal.
> 
> The reason for spacing the wire is to reduce Proximity effect.
> 
> 
> Here is the graph, each coil was tested twice (two lines each)
> 
> 
> 
> > http://s395.photobucket.com/user/Qmavam/media/Close%20vs%20space%20wound._zpsctlfmjdi.png.html
> 
> 
> What would be the reason that the Q does not start out higher,
> but moves up with frequency?

I always find some loss in the capacitor part of an LC.  
Lower frequency is bigger C, is the loss there?  

George H. 
> 
> 
> 
>                                       Mikek
> 
> Re: the difference in inductance, both 40 turns.
> The inductance,  215uh vs 187uh = 86.9%
> The capacitance 7.7 vs 6.9 = 89.6%
> The capacitance of 40 turns did go down 10.3% with spacing.
> The inductance went down 13% with spacing.   FWIW

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#429817

On 9/29/2016 8:55 AM, George Herold wrote:
> On Wednesday, September 28, 2016 at 2:42:14 PM UTC-4, amdx wrote:
>> A fine gentleman did an experiment building two inductors.
>> The coils were wound with 420/46 litz. Both inductors have 40 turns.
>> One inductor is close wound (215uh 7.7pf distributed capacitance).
>> The second has a 0.625/wire diameter space between wires, (187uh and 6.9
>> pf distributed capacitance).
>>    The inductor with spacing has a higher Q, except at the low end
>>
>> where the Q's are equal.
>>
>> The reason for spacing the wire is to reduce Proximity effect.
>>
>>
>> Here is the graph, each coil was tested twice (two lines each)
>>
>>
>>
>>> http://s395.photobucket.com/user/Qmavam/media/Close%20vs%20space%20wound._zpsctlfmjdi.png.html
>>
>>
>> What would be the reason that the Q does not start out higher,
>> but moves up with frequency?
>

>
> George H.
>>
>>
>>
>>                                       Mikek
>>
>> Re: the difference in inductance, both 40 turns.
>> The inductance,  215uh vs 187uh = 86.9%
>> The capacitance 7.7 vs 6.9 = 89.6%
>> The capacitance of 40 turns did go down 10.3% with spacing.
>> The inductance went down 13% with spacing.   FWIW

> > I always find some loss in the capacitor part of an LC.

> Lower frequency is bigger C, is the loss there?

  That's a good thought, I'm leaning against it though,
I suspect my fine gentleman measured his inductors with either a Boonton 
260A or an HP 4342A, both of these use very high Q* capacitors,
so even if the cap had more loss at low frequencies, I don't think it 
would make that much difference in the Q curve.

* ISTR reading the Boonton 260A tuning capacitor has a Q near 20,000.
I recently saw some silver air variable caps with a Q of 15,000.
Run of the mill air variables run from 1,000 on up.

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#429820

> 
>   That's a good thought, I'm leaning against it though,
> I suspect my fine gentleman measured his inductors with either a Boonton 
> 260A or an HP 4342A, both of these use very high Q* capacitors,
> so even if the cap had more loss at low frequencies, I don't think it 
> would make that much difference in the Q curve.
> 
> * ISTR reading the Boonton 260A tuning capacitor has a Q near 20,000.
> I recently saw some silver air variable caps with a Q of 15,000.
> Run of the mill air variables run from 1,000 on up.

Any C (an actual C or parasitic C) across an L increases the Z and therefore increases the "effective" value of L.  Since the R is unchanged, the Q of the effective increased L is increased also.   This works up to the SRF, but of course not above SRF.

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#429831

On 9/29/2016 11:15 AM, makolber@yahoo.com wrote:
>
>>
>>   That's a good thought, I'm leaning against it though,
>> I suspect my fine gentleman measured his inductors with either a Boonton
>> 260A or an HP 4342A, both of these use very high Q* capacitors,
>> so even if the cap had more loss at low frequencies, I don't think it
>> would make that much difference in the Q curve.
>>
>> * ISTR reading the Boonton 260A tuning capacitor has a Q near 20,000.
>> I recently saw some silver air variable caps with a Q of 15,000.
>> Run of the mill air variables run from 1,000 on up.


> Any C (an actual C or parasitic C) across an L increases the Z and therefore increases the "effective" value of L.
>Since the R is unchanged, the Q of the effective increased L is increased also.
>This works up to the SRF, but of course not above SRF.

Is this true at Resonance? My math is very weak, but I can't make that 
happen at resonance.

                                     Mikek

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