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Choke winding question

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  Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 15:42 +0000
    Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-15 09:48 -0700
      Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 17:03 +0000
    Re: Choke winding question John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-15 10:29 -0700
      Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-15 11:37 -0700
      Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 22:02 +0000
        Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-15 15:16 -0700
          Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 23:36 +0000
            Re: Choke winding question rickman <gnuarm@gmail.com> - 2017-03-15 21:41 -0400
              Re: Choke winding question Phil Allison <pallison49@gmail.com> - 2017-03-15 19:28 -0700
              Re: Choke winding question bill.sloman@ieee.org - 2017-03-15 20:12 -0700
                Re: Choke winding question rickman <gnuarm@gmail.com> - 2017-03-16 00:00 -0400
                  Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-16 09:03 +0000
                Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-16 05:56 -0700
                  Re: Choke winding question bill.sloman@ieee.org - 2017-03-16 09:42 -0700
    Re: Choke winding question legg <legg@nospam.magma.ca> - 2017-03-15 19:23 -0400
    Re: Choke winding question "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-15 22:56 -0500
      Re: Choke winding question Phil Allison <pallison49@gmail.com> - 2017-03-15 22:30 -0700
        Re: Choke winding question "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-16 15:08 -0500

#451954 — Choke winding question

I was using a Ferroxcube calculator to work out some choke windings. 
These have to be multiple RM12, about 5mH and 2.5A DC, so I was looking 
at the maximum inductance before saturation for different cores.

A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
or 3 x 250nH cores with 89 turns, 2000uH each
or 10 x 1000nH cores with 22 turns, 500uH each.

The 400nH cores are probably best, 89 turns won't fit with reasonably 
thick wire and 10 cores is painful.

However - it seems that the /total/ number of turns is about constant. 
Is that a rule of thumb, just normal or just lucky?

Cheers
-- 
Clive

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#451965

Clive Arthur wrote...
>
>I was using a Ferroxcube calculator to work out some choke windings. 
>These have to be multiple RM12, about 5mH and 2.5A DC, so I was looking 
>at the maximum inductance before saturation for different cores.
>
>A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
>or 3 x 250nH cores with 89 turns, 2000uH each
>or 10 x 1000nH cores with 22 turns, 500uH each.
>
>The 400nH cores are probably best, 89 turns won't fit with reasonably 
>thick wire and 10 cores is painful.
>
>However - it seems that the /total/ number of turns is about constant. 
>Is that a rule of thumb, just normal or just lucky?

 Did you play with the gap size?


-- 
 Thanks,
    - Win

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#451969

On 15/03/2017 16:48, Winfield Hill wrote:
> Clive Arthur wrote...
>>
>> I was using a Ferroxcube calculator to work out some choke windings.
>> These have to be multiple RM12, about 5mH and 2.5A DC, so I was looking
>> at the maximum inductance before saturation for different cores.
>>
>> A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
>> or 3 x 250nH cores with 89 turns, 2000uH each
>> or 10 x 1000nH cores with 22 turns, 500uH each.
>>
>> The 400nH cores are probably best, 89 turns won't fit with reasonably
>> thick wire and 10 cores is painful.
>>
>> However - it seems that the /total/ number of turns is about constant.
>> Is that a rule of thumb, just normal or just lucky?
>
>  Did you play with the gap size?
>
>
The three cores modelled are the same ferrite material and the same size 
(RM12), they have different gaps giving them different Al values...

250nH = 901um
400nH = 511um
1000nH = 171um

Cheers
-- 
Clive

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#451973

On Wed, 15 Mar 2017 15:42:45 +0000, Clive Arthur
<cliveta@nowaytoday.co.uk> wrote:

>I was using a Ferroxcube calculator to work out some choke windings. 
>These have to be multiple RM12, about 5mH and 2.5A DC, so I was looking 
>at the maximum inductance before saturation for different cores.
>
>A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
>or 3 x 250nH cores with 89 turns, 2000uH each
>or 10 x 1000nH cores with 22 turns, 500uH each.
>
>The 400nH cores are probably best, 89 turns won't fit with reasonably 
>thick wire and 10 cores is painful.
>
>However - it seems that the /total/ number of turns is about constant. 
>Is that a rule of thumb, just normal or just lucky?
>
>Cheers

You can't just buy something from Coilcraft?


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#451986

John Larkin wrote...
>
> Clive Arthur wrote:
>
>> multiple RM12, about 5mH and 2.5A DC, 
>
> You can't just buy something from Coilcraft?

 They don't have much in the way of high-inductance
 high-current inductors.  Everybody wants small, 
 high-frequency stuff these days.  I want large
 high-voltage high-frequency high-power stuff.
 Well, at least it doesn't require too many turns.


-- 
 Thanks,
    - Win

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#452010

On 15/03/2017 17:29, John Larkin wrote:
> On Wed, 15 Mar 2017 15:42:45 +0000, Clive Arthur
> <cliveta@nowaytoday.co.uk> wrote:
>
>> I was using a Ferroxcube calculator to work out some choke windings.
>> These have to be multiple RM12, about 5mH and 2.5A DC, so I was looking
>> at the maximum inductance before saturation for different cores.
>>
>> A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
>> or 3 x 250nH cores with 89 turns, 2000uH each
>> or 10 x 1000nH cores with 22 turns, 500uH each.
>>
>> The 400nH cores are probably best, 89 turns won't fit with reasonably
>> thick wire and 10 cores is painful.
>>
>> However - it seems that the /total/ number of turns is about constant.
>> Is that a rule of thumb, just normal or just lucky?
>>
>> Cheers
>
> You can't just buy something from Coilcraft?

Well, that wouldn't answer my question.

Anyway, high voltage, high temperature, constrained space mean not COTS.

Cheers
-- 
Clive

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#452015

Clive Arthur wrote...
>
 What frequency are you choking?


-- 
 Thanks,
    - Win

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#452027

On 15/03/2017 22:16, Winfield Hill wrote:
> Clive Arthur wrote...
>>
>  What frequency are you choking?
>
>
10kHz to 100kHz.

But my question is simpler, I probably haven't explained it well.  When 
I use a manufacturers PC software to see what's the most inductance I 
can get from an RM12 core with 2.5A DC going through it without it 
saturating, accepting that I will need multiple chokes in series to 
attain 5mH, it seems that the /total/ number of turns required is much 
the same.  Is that physics or just luck?

According to the Ferroxcube software, a 400nH core with 57 turns giving 
1.3mH saturates at 2.5A, so to get 5mH I'd need 4 of these, giving 228 
total turns for 5.2mH or 22uH/T

250nH, 89T, 2.5A, 2mH, 3 needed, 267T for 6mH or 22uH/T

1000nH core, 22T, 2.5A, 500uH, 10 needed, 220T for 5mH  or 23uH/T

All the same core material, 3 different gaps for 3 different Al figures.

It seems suspicious that these three configurations come up with the 
same total number of turns for the same inductance at the same 
saturation current.  Is this something simple which is well known in the 
choke-winding fraternity, is it coincidence, or is it an inevitable 
consequence of inductor physics?  It may well be an obvious thing which 
I simply didn't know.

Cheers
-- 
Clive

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#452053

On 3/15/2017 7:36 PM, Clive Arthur wrote:
> On 15/03/2017 22:16, Winfield Hill wrote:
>> Clive Arthur wrote...
>>>
>>  What frequency are you choking?
>>
>>
> 10kHz to 100kHz.
>
> But my question is simpler, I probably haven't explained it well.  When
> I use a manufacturers PC software to see what's the most inductance I
> can get from an RM12 core with 2.5A DC going through it without it
> saturating, accepting that I will need multiple chokes in series to
> attain 5mH, it seems that the /total/ number of turns required is much
> the same.  Is that physics or just luck?
>
> According to the Ferroxcube software, a 400nH core with 57 turns giving
> 1.3mH saturates at 2.5A, so to get 5mH I'd need 4 of these, giving 228
> total turns for 5.2mH or 22uH/T
>
> 250nH, 89T, 2.5A, 2mH, 3 needed, 267T for 6mH or 22uH/T
>
> 1000nH core, 22T, 2.5A, 500uH, 10 needed, 220T for 5mH  or 23uH/T
>
> All the same core material, 3 different gaps for 3 different Al figures.
>
> It seems suspicious that these three configurations come up with the
> same total number of turns for the same inductance at the same
> saturation current.  Is this something simple which is well known in the
> choke-winding fraternity, is it coincidence, or is it an inevitable
> consequence of inductor physics?  It may well be an obvious thing which
> I simply didn't know.

What is different about the cores that give them the different ratings? 
Is it size, materials, what?  Are the winding dimensions the same?  What 
is the same vs. what is different?

-- 

Rick C

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#452065

Prickman wrote:


> 
> >
> > All the same core material, 3 different gaps for 3 different Al figures.
> >
> > 
> What is different about the cores that give them the different ratings? 
> Is it size, materials, what?  Are the winding dimensions the same?  What 
> is the same vs. what is different?
> 
> 


 ** FFS dickhead -   try bloody READING people's posts !!!!




....   Phil  

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#452073

On Thursday, March 16, 2017 at 12:41:17 PM UTC+11, rickman wrote:
> On 3/15/2017 7:36 PM, Clive Arthur wrote:
> > On 15/03/2017 22:16, Winfield Hill wrote:
> >> Clive Arthur wrote...
> >>>
> >>  What frequency are you choking?
> >>
> >>
> > 10kHz to 100kHz.
> >
> > But my question is simpler, I probably haven't explained it well.  When
> > I use a manufacturers PC software to see what's the most inductance I
> > can get from an RM12 core with 2.5A DC going through it without it
> > saturating, accepting that I will need multiple chokes in series to
> > attain 5mH, it seems that the /total/ number of turns required is much
> > the same.  Is that physics or just luck?
> >
> > According to the Ferroxcube software, a 400nH core with 57 turns giving
> > 1.3mH saturates at 2.5A, so to get 5mH I'd need 4 of these, giving 228
> > total turns for 5.2mH or 22uH/T
> >
> > 250nH, 89T, 2.5A, 2mH, 3 needed, 267T for 6mH or 22uH/T
> >
> > 1000nH core, 22T, 2.5A, 500uH, 10 needed, 220T for 5mH  or 23uH/T
> >
> > All the same core material, 3 different gaps for 3 different Al figures.
> >
> > It seems suspicious that these three configurations come up with the
> > same total number of turns for the same inductance at the same
> > saturation current.  Is this something simple which is well known in the
> > choke-winding fraternity, is it coincidence, or is it an inevitable
> > consequence of inductor physics?  It may well be an obvious thing which
> > I simply didn't know.
> 
> What is different about the cores that give them the different ratings? 
> Is it size, materials, what?  Are the winding dimensions the same?  What 
> is the same vs. what is different?

Gap. The Ferroxcube RM12 core range offers a small series of cores with the same external dimensions, but with a progressively large gap in the centre leg.

http://www.ferroxcube.com/FerroxcubeCorporateReception/datasheet/rm12i.pdf

The effective magnetic path length for all of them is 56.6mm, but the largest gap - 1.57mm - is equivalent to more than a metre of path length in ferrite and dominates the inductance of any coil wound on the core.

Whence the 160nH per root turn for a core which offers 5.6uH when ungapped.

The EPCOS data sheet isn't much different

https://en.tdk.eu/inf/80/db/fer_13/rm_12.pdf

but their application notes used to be a whole lot better.

https://en.tdk.eu/blob/2078018/20e26ff3aff21de38c410d79990ddeb6/ferrites-db-17-pdf-data.pdf

is 6688 pages and 33.15 MB. It's more comprehensive than accessible.

The late great Tony Williams circulated a bunch of  the more useful material to his friends some ten years ago in smaller chunks.

-- 
Bill Sloman, Sydney

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#452078

On 3/15/2017 11:12 PM, bill.sloman@ieee.org wrote:
> On Thursday, March 16, 2017 at 12:41:17 PM UTC+11, rickman wrote:
>> On 3/15/2017 7:36 PM, Clive Arthur wrote:
>>> On 15/03/2017 22:16, Winfield Hill wrote:
>>>> Clive Arthur wrote...
>>>>>
>>>> What frequency are you choking?
>>>>
>>>>
>>> 10kHz to 100kHz.
>>>
>>> But my question is simpler, I probably haven't explained it well.
>>> When I use a manufacturers PC software to see what's the most
>>> inductance I can get from an RM12 core with 2.5A DC going through
>>> it without it saturating, accepting that I will need multiple
>>> chokes in series to attain 5mH, it seems that the /total/ number
>>> of turns required is much the same.  Is that physics or just
>>> luck?
>>>
>>> According to the Ferroxcube software, a 400nH core with 57 turns
>>> giving 1.3mH saturates at 2.5A, so to get 5mH I'd need 4 of
>>> these, giving 228 total turns for 5.2mH or 22uH/T
>>>
>>> 250nH, 89T, 2.5A, 2mH, 3 needed, 267T for 6mH or 22uH/T
>>>
>>> 1000nH core, 22T, 2.5A, 500uH, 10 needed, 220T for 5mH  or
>>> 23uH/T
>>>
>>> All the same core material, 3 different gaps for 3 different Al
>>> figures.
>>>
>>> It seems suspicious that these three configurations come up with
>>> the same total number of turns for the same inductance at the
>>> same saturation current.  Is this something simple which is well
>>> known in the choke-winding fraternity, is it coincidence, or is
>>> it an inevitable consequence of inductor physics?  It may well be
>>> an obvious thing which I simply didn't know.
>>
>> What is different about the cores that give them the different
>> ratings? Is it size, materials, what?  Are the winding dimensions
>> the same?  What is the same vs. what is different?
>
> Gap. The Ferroxcube RM12 core range offers a small series of cores
> with the same external dimensions, but with a progressively large gap
> in the centre leg.
>
> http://www.ferroxcube.com/FerroxcubeCorporateReception/datasheet/rm12i.pdf
>
>  The effective magnetic path length for all of them is 56.6mm, but
> the largest gap - 1.57mm - is equivalent to more than a metre of path
> length in ferrite and dominates the inductance of any coil wound on
> the core.
>
> Whence the 160nH per root turn for a core which offers 5.6uH when
> ungapped.
>
> The EPCOS data sheet isn't much different
>
> https://en.tdk.eu/inf/80/db/fer_13/rm_12.pdf
>
> but their application notes used to be a whole lot better.
>
> https://en.tdk.eu/blob/2078018/20e26ff3aff21de38c410d79990ddeb6/ferrites-db-17-pdf-data.pdf
>
>  is 6688 pages and 33.15 MB. It's more comprehensive than
> accessible.
>
> The late great Tony Williams circulated a bunch of  the more useful
> material to his friends some ten years ago in smaller chunks.

Thanks for the info.  As to the cores, Clive says he is using the RM12 
cores in 250, 400 and 1000 nH.  But I don't see a 1000 nH core listed.

-- 

Rick C

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#452100

On 16/03/2017 04:00, rickman wrote:
> On 3/15/2017 11:12 PM, bill.sloman@ieee.org wrote:
>> On Thursday, March 16, 2017 at 12:41:17 PM UTC+11, rickman wrote:
>>> On 3/15/2017 7:36 PM, Clive Arthur wrote:
>>>> On 15/03/2017 22:16, Winfield Hill wrote:
>>>>> Clive Arthur wrote...
>>>>>>
>>>>> What frequency are you choking?
>>>>>
>>>>>
>>>> 10kHz to 100kHz.
>>>>
>>>> But my question is simpler, I probably haven't explained it well.
>>>> When I use a manufacturers PC software to see what's the most
>>>> inductance I can get from an RM12 core with 2.5A DC going through
>>>> it without it saturating, accepting that I will need multiple
>>>> chokes in series to attain 5mH, it seems that the /total/ number
>>>> of turns required is much the same.  Is that physics or just
>>>> luck?
>>>>
>>>> According to the Ferroxcube software, a 400nH core with 57 turns
>>>> giving 1.3mH saturates at 2.5A, so to get 5mH I'd need 4 of
>>>> these, giving 228 total turns for 5.2mH or 22uH/T
>>>>
>>>> 250nH, 89T, 2.5A, 2mH, 3 needed, 267T for 6mH or 22uH/T
>>>>
>>>> 1000nH core, 22T, 2.5A, 500uH, 10 needed, 220T for 5mH  or
>>>> 23uH/T
>>>>
>>>> All the same core material, 3 different gaps for 3 different Al
>>>> figures.
>>>>
>>>> It seems suspicious that these three configurations come up with
>>>> the same total number of turns for the same inductance at the
>>>> same saturation current.  Is this something simple which is well
>>>> known in the choke-winding fraternity, is it coincidence, or is
>>>> it an inevitable consequence of inductor physics?  It may well be
>>>> an obvious thing which I simply didn't know.
>>>
>>> What is different about the cores that give them the different
>>> ratings? Is it size, materials, what?  Are the winding dimensions
>>> the same?  What is the same vs. what is different?
>>
>> Gap. The Ferroxcube RM12 core range offers a small series of cores
>> with the same external dimensions, but with a progressively large gap
>> in the centre leg.
>>
>> http://www.ferroxcube.com/FerroxcubeCorporateReception/datasheet/rm12i.pdf
>>
>>
>>  The effective magnetic path length for all of them is 56.6mm, but
>> the largest gap - 1.57mm - is equivalent to more than a metre of path
>> length in ferrite and dominates the inductance of any coil wound on
>> the core.
>>
>> Whence the 160nH per root turn for a core which offers 5.6uH when
>> ungapped.
>>
>> The EPCOS data sheet isn't much different
>>
>> https://en.tdk.eu/inf/80/db/fer_13/rm_12.pdf
>>
>> but their application notes used to be a whole lot better.
>>
>> https://en.tdk.eu/blob/2078018/20e26ff3aff21de38c410d79990ddeb6/ferrites-db-17-pdf-data.pdf
>>
>>
>>  is 6688 pages and 33.15 MB. It's more comprehensive than
>> accessible.
>>
>> The late great Tony Williams circulated a bunch of  the more useful
>> material to his friends some ten years ago in smaller chunks.
>
> Thanks for the info.  As to the cores, Clive says he is using the RM12
> cores in 250, 400 and 1000 nH.  But I don't see a 1000 nH core listed.
>
I'm not using them, I'm using their design software to work out what I 
need.  If there's no Ferroxcube 1000nH, there'll be an Epcos.

Incidentally, running the same program on a 5300nH core gives 100uH, 4 
turns, 2.5A turns, 50 cores needed and 25uH/T which is still pretty 
close to my observation, ie I'd need 200 turns total across 50 cores for 
5mH at 2.5A.

This may be obvious to someone 'skilled in the art', but it's new to me.

Cheers
-- 
Clive

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#452107

bill.sloman@ieee.org wrote...
>
>https://en.tdk.eu/blob/2078018/20e26ff3aff21de38c410d79990ddeb6/ferrites-db-17-pdf-data.pdf
> is 6688 pages and 33.15 MB. It's more comprehensive than accessible.

 That's 688 pages.


-- 
 Thanks,
    - Win

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#452131

On Thursday, March 16, 2017 at 11:57:11 PM UTC+11, Winfield Hill wrote:
> bill.sloman@ieee.org wrote...
> >
> >https://en.tdk.eu/blob/2078018/20e26ff3aff21de38c410d79990ddeb6/ferrites-db-17-pdf-data.pdf
> > is 6688 pages and 33.15 MB. It's more comprehensive than accessible.
> 
>  That's 688 pages.

Oops. That's what I meant to type.

-- 
Bill Sloman, Sydney

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#452024

On Wed, 15 Mar 2017 15:42:45 +0000, Clive Arthur
<cliveta@nowaytoday.co.uk> wrote:

>I was using a Ferroxcube calculator to work out some choke windings. 
>These have to be multiple RM12, about 5mH and 2.5A DC, so I was looking 
>at the maximum inductance before saturation for different cores.
>
>A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
>or 3 x 250nH cores with 89 turns, 2000uH each
>or 10 x 1000nH cores with 22 turns, 500uH each.
>
>The 400nH cores are probably best, 89 turns won't fit with reasonably 
>thick wire and 10 cores is painful.
>
>However - it seems that the /total/ number of turns is about constant. 
>Is that a rule of thumb, just normal or just lucky?
>
>Cheers

You've just run into the Hanna curves.

RL

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#452077

Saturation occurs at the same N*I for a given core shape and size, 
independent of gap*.

*Not quite independent due to fringing, but in the small-gap limit, this 
works.

Physically, this is because Ae is the same, and you can only pack so much 
flux density Bsat into the core.  Bsat (== Vs/mm^2) * Ae (== mm^2) == Vs 
(flux, integral V dt applied to the core).

The average (or effective) permeability that's best depends on a number of 
optimization factors, but it's in the 20-60 range.  The lower A_L cores in 
that selection will have this property.

As you note, lower mu_eff is higher energy (because the energy is stored in 
the air gap, which is larger), but harder to wind (takes more copper for the 
same losses).  (If we had superconductors, a very low mu_eff would be 
manageable, and we could do air-core inductors without worry.)

Tim

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


"Clive Arthur" <cliveta@nowaytoday.co.uk> wrote in message 
news:oabn87$5ag$1@dont-email.me...
>I was using a Ferroxcube calculator to work out some choke windings. These 
>have to be multiple RM12, about 5mH and 2.5A DC, so I was looking at the 
>maximum inductance before saturation for different cores.
>
> A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
> or 3 x 250nH cores with 89 turns, 2000uH each
> or 10 x 1000nH cores with 22 turns, 500uH each.
>
> The 400nH cores are probably best, 89 turns won't fit with reasonably 
> thick wire and 10 cores is painful.
>
> However - it seems that the /total/ number of turns is about constant. Is 
> that a rule of thumb, just normal or just lucky?
>
> Cheers
> -- 
> Clive 

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#452087

 Tim Williams wrote:
>
> Saturation occurs at the same N*I for a given core shape and size, 
> independent of gap*.
> 
> 

 ** Huh ???

 You out of your mind ?? 

 For the same winding, increasing the gap increases sat current. 

 It's the reason for adding a damn gap !!! 



....  Phil 

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#452166

"Phil Allison" <pallison49@gmail.com> wrote in message 
news:020c3dde-ada1-4eef-a712-6840cb96f44c@googlegroups.com...
>> Saturation occurs at the same N*I for a given core shape and size,
>> independent of gap*.
>
> For the same winding, increasing the gap increases sat current.

Buh, why did I type N*I?  I even said flux is constant later...
(Thanks Phil)

Tim

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

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