Gapped potcore/ E core AsubLs

[amdx]

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

 

[Tim Williams]

Equivalent permeability goes as:
mu_eq = l_e / [l_g + (l_e / mu_r)]

Tim

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

"amdx" <nojunk@knology.net> wrote in message
news:ql887p$68q$1@dont-email.me...

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

 

[Mikko OH2HVJ]

amdx <nojunk@knology.net> writes:

Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

The permeability of the core material is high compared to the air gap,
so the magnetic field is almost all in the air gap. Thus, the gap almost
fully determines the AsubL.

--
mikko

 

On Tue, 10 Sep 2019 08:25:12 -0500, amdx <nojunk@knology.net> wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

It does, but not "in proportion". It's like resistances in series.

Somebody is being lazy.

 

[amdx]

On 9/10/2019 10:07 AM, jlarkin@highlandsniptechnology.com wrote:

On Tue, 10 Sep 2019 08:25:12 -0500, amdx <nojunk@knology.net> wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

It does, but not "in proportion". It's like resistances in series.

Somebody is being lazy.

No, not being lazy, just no math skills and trying to understand ferrites.

My real problem at the moment is trying to identify the material of an
E core I have with a 0.225" gap.
Even with that huge gap, it has an AsubL of 3500. Just now realized
that is so high, maybe I did something wrong to get that number. (all
four times!)

With 337 turns inductance equals 401mH @10kHz AL=3530

With 387 turns inductance equals 528mH @10kHz AL=3525

With 724 turns inductance equals 1819mH @10kHz AL=3470

With 100 turns inductance equals 29mH @10kHz AL=2900

See any error with my AsubL calculation.
Seems huge with a large gap. Am I off by a factor of 100?

The point where U' and u" cross is about 365kHz.

E core size is 55.2/27.6/20.7
(hmm wanted post a dropbox image of core and dimensions, but copy link
won't highlight)

Mikek

 

On Tuesday, September 10, 2019 at 8:25:19 AM UTC-5, amdx wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in the outer legs, the gap is just like a high value parallel resistor adding the the flux, but not much. To bring the gap into the picture I need to connect the two coils series opposing.
Mikek

 

[John Larkin]

On Tue, 10 Sep 2019 10:44:53 -0500, amdx <nojunk@knology.net> wrote:

On 9/10/2019 10:07 AM, jlarkin@highlandsniptechnology.com wrote:
On Tue, 10 Sep 2019 08:25:12 -0500, amdx <nojunk@knology.net> wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

It does, but not "in proportion". It's like resistances in series.

Somebody is being lazy.


No, not being lazy, just no math skills and trying to understand ferrites.

I didn't mean you, but the Ferroxcube people.

 

[Tim Williams]

<amdx62@gmail.com> wrote in message
news:634ca0e0-871c-4e31-bd66-4c8ae69f78e6@googlegroups.com...
>I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer
legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in
the outer legs, the gap is just like a high value parallel resistor adding
the the flux, but not much. To bring the gap into the picture I need to
connect the two coils series opposing.
>

Oh yeah, for the two windings outside and the gap in the middle, that's
quite correct -- note that you need to use a different l_e to calculate
mu_r, since the path is all the way around, not through the middle.

But that is a measurement you can use now.

And to find the core material cutoff frequency, you can plot Q(F), but mind
you'll probably need to do so with many fewer turns to get meaningful
results.

Tim

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

 

On Tuesday, September 10, 2019 at 2:16:33 PM UTC-5, Tim Williams wrote:

amdx62@gmail.com> wrote in message
news:634ca0e0-871c-4e31-bd66-4c8ae69f78e6@googlegroups.com...
I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer
legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in
the outer legs, the gap is just like a high value parallel resistor adding
the the flux, but not much. To bring the gap into the picture I need to
connect the two coils series opposing.


Oh yeah, for the two windings outside and the gap in the middle, that's
quite correct -- note that you need to use a different l_e to calculate
mu_r, since the path is all the way around, not through the middle.

But that is a measurement you can use now.

And to find the core material cutoff frequency, you can plot Q(F), but mind
you'll probably need to do so with many fewer turns to get meaningful
results.

Tim

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

Term definition verification.
l_e is that effective length.
Mu_r is that relative permeability u'

By cutoff frequency do you mean where u' and u" cross?
If yes, I got about 365kHz. using 6 turns.
I'm not sure what Q(F) is.
Would that be plotting core Q and looking for a matching permeability graphs?

Thanks, Mikek

 

[amdx]

On 9/10/2019 1:44 PM, John Larkin wrote:

On Tue, 10 Sep 2019 10:44:53 -0500, amdx <nojunk@knology.net> wrote:

On 9/10/2019 10:07 AM, jlarkin@highlandsniptechnology.com wrote:
On Tue, 10 Sep 2019 08:25:12 -0500, amdx <nojunk@knology.net> wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

It does, but not "in proportion". It's like resistances in series.

Somebody is being lazy.


No, not being lazy, just no math skills and trying to understand ferrites.

I didn't mean you, but the Ferroxcube people.

Ah, not sure that's true, I might not have presented what you aren't seeing.
First, I don't know who made my core, (junkbox find).
Second, it had a strange gap, it was only cut through about 80%,
20% of the center leg was not gapped.
Until I chipped it, then I ground it all out.
I don't know if I have mentioned it here, in this large gap I'm
sliding a toroid in as far as I can, with enough turns to make it a 120uh.
Then applying DC to the E core to saturate the toroid.
So far all is working well, except. I want a high frequency material
for my toroid, (will order) and I don't know what my E core is, so I
can't order until I figure it out.
The one characteristic I think I gave a handle on is where u' and u"
cross on the permeability graph, My E core is about 365kHz.
I'm happy with this material because it does not seem to have any
remanence. My first core did. (3 iron washers with a slot cut)
Mikek

 

[amdx]

On 9/10/2019 3:35 PM, amdx62@gmail.com wrote:

On Tuesday, September 10, 2019 at 2:16:33 PM UTC-5, Tim Williams wrote:
amdx62@gmail.com> wrote in message
news:634ca0e0-871c-4e31-bd66-4c8ae69f78e6@googlegroups.com...
I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer
legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in
the outer legs, the gap is just like a high value parallel resistor adding
the the flux, but not much. To bring the gap into the picture I need to
connect the two coils series opposing.


Oh yeah, for the two windings outside and the gap in the middle, that's
quite correct -- note that you need to use a different l_e to calculate
mu_r, since the path is all the way around, not through the middle.

But that is a measurement you can use now.

And to find the core material cutoff frequency, you can plot Q(F), but mind
you'll probably need to do so with many fewer turns to get meaningful
results.

Tim

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

Term definition verification.
l_e is that effective length.
Mu_r is that relative permeability u'

By cutoff frequency do you mean where u' and u" cross?
If yes, I got about 365kHz. using 6 turns.
I'm not sure what Q(F) is.
Would that be plotting core Q and looking for a matching permeability graphs?

Thanks, Mikek

For l_e would I use the length around the core but centered inside the
core. Should I just ignore the center leg for this measurement.

FWIW. I put the 5000 permeability toroid in the gap, it's tight.
Then I measured the inductance to calculate the AsubL, I did this with
the coils connected series opposing so the center leg is being used.
I got the same AsubL as all my other measurements about 3500.
Making me think I could use the published l_e 0f 124mm.

Thanks for your help, Mikek

 

[Tim Williams]

"amdx" <nojunk@knology.net> wrote in message
news:ql920r$5gf$1@dont-email.me...

Term definition verification.
l_e is that effective length.
Mu_r is that relative permeability u'

Yes. Close. mu_r is |u|. Use the vector sum, technically. Since air has
mu'' = 0.

By cutoff frequency do you mean where u' and u" cross?
If yes, I got about 365kHz. using 6 turns.
I'm not sure what Q(F) is.
Would that be plotting core Q and looking for a matching permeability
graphs?

Yes, "Q as a function of frequency". Q = 1 being u' = u''.

For l_e would I use the length around the core but centered inside the
core. Should I just ignore the center leg for this measurement.

Yes. l_e appears to be pretty close to midline in the core, maybe rounding
off the corners a little bit.

Same thing with v_e, in case you're wondering. Typically very close to A_e
* l_e. There could be dead weight on a core, I guess, but it also won't be
active volume, so it makes sense to be nearby. (You probably won't need to
know this until you're calculating total core losses.)

Tim

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

 

[amdx]

On 9/10/2019 3:45 PM, amdx wrote:

On 9/10/2019 3:35 PM, amdx62@gmail.com wrote:
On Tuesday, September 10, 2019 at 2:16:33 PM UTC-5, Tim Williams wrote:
amdx62@gmail.com> wrote in message
news:634ca0e0-871c-4e31-bd66-4c8ae69f78e6@googlegroups.com...
I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on
the outer
legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating
mostly in
the outer legs, the gap is just like a high value parallel resistor
adding
the the flux, but not much. To bring the gap into the picture I need to
connect the two coils series opposing.


Oh yeah, for the two windings outside and the gap in the middle, that's
quite correct -- note that you need to use a different l_e to calculate
mu_r, since the path is all the way around, not through the middle.

But that is a measurement you can use now.

And to find the core material cutoff frequency, you can plot Q(F),
but mind
you'll probably need to do so with many fewer turns to get meaningful
results.

Tim

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

Term definition verification.
l_e is that effective length.
Mu_r is that relative permeability u'

Ok, I'm satisfied I have those right.




>> By cutoff frequency do you mean where u' and u" cross?

Google has not been my friend for this.

If yes, I got about 365kHz. using 6 turns.
I'm not sure what Q(F) is.
Would that be plotting core Q and looking for a matching permeability
graphs?

No luck finding Q(F)

                          Thanks, Mikek

 

[legg]

On Tue, 10 Sep 2019 08:07:19 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 10 Sep 2019 08:25:12 -0500, amdx <nojunk@knology.net> wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

It does, but not "in proportion". It's like resistances in series.

Somebody is being lazy.

Not lazy, when one of them has a 10^-7 exponent, to dominate in the
numerator of a fraction.

RL

 

[legg]

On Tue, 10 Sep 2019 09:43:22 -0700 (PDT), amdx62@gmail.com wrote:

On Tuesday, September 10, 2019 at 8:25:19 AM UTC-5, amdx wrote:
While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in the outer legs, the gap is just like a high value parallel resistor adding the the flux, but not much. To bring the gap into the picture I need to connect the two coils series opposing.
Mikek

If connected in series, the center core leg will be invisible.

If connected in parallel, it's a mess.

Operating independantly, it's a can of worms.

RL

 

[amdx]

On 9/11/2019 9:14 AM, legg wrote:

On Tue, 10 Sep 2019 08:07:19 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 10 Sep 2019 08:25:12 -0500, amdx <nojunk@knology.net> wrote:

While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

It does, but not "in proportion". It's like resistances in series.

Somebody is being lazy.

Not lazy, when one of them has a 10^-7 exponent, to dominate in the
numerator of a fraction.

RL

I still don't understand where they were lazy.
But, there are a lot of things I'd like to see on the Ferrite datasheet
that isn't there. Lately it is a remanence number so I could pick a
material on the low end of the scale.
One of the calcs I did with the 10^-7 also had a 10^6
in it so I ended up with 1.256 as a result, in the denominator.
If I was 14 again, I would start a study of math and physics/electronics
and practice math some more. I'm 50 years late in knowing what I want to
be when I grow up.
Mikek

 

[amdx]

On 9/11/2019 9:17 AM, legg wrote:

On Tue, 10 Sep 2019 09:43:22 -0700 (PDT), amdx62@gmail.com wrote:

On Tuesday, September 10, 2019 at 8:25:19 AM UTC-5, amdx wrote:
While looking through the Ferroxcube Ferrites databook, I see a specific
size core with gaps for several different materials.
These materials have a nongapped AsubL ranging from 4600 to 6950.
If the gap in all the materials is 270um the AsubL drops to 1000.
With the same size gap, even though they start with different AsubLs,
the now all have the same AsubL.
Example:
3F3 non-gapped AsubL=4600 with a 240um gap AsubL = 1000.
3C81 non-gapped AsubL=6950 with a 240um gap AsubL = 1000.
Why doesn't gapped AsubL change in proportion with the original AsubL?

Mikek

I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in the outer legs, the gap is just like a high value parallel resistor adding the the flux, but not much. To bring the gap into the picture I need to connect the two coils series opposing.
Mikek

If connected in series, the center core leg will be invisible.

It will be connected series opposing with equal turns on each leg.
This puts maximum flux on center leg.

If connected in parallel, it's a mess.

Not sure why if equal turns and opposing.
Might look into this, lowers operating voltage by 1/2.

Operating independantly, it's a can of worms.

No need to explore that.

Mikek

RL

 

[legg]

On Wed, 11 Sep 2019 15:34:21 -0500, amdx <nojunk@knology.net> wrote:

On 9/11/2019 9:17 AM, legg wrote:
On Tue, 10 Sep 2019 09:43:22 -0700 (PDT), amdx62@gmail.com wrote:

snip> Mikek

I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in the outer legs, the gap is just like a high value parallel resistor adding the the flux, but not much. To bring the gap into the picture I need to connect the two coils series opposing.
Mikek

If connected in series, the center core leg will be invisible.

It will be connected series opposing with equal turns on each leg.
This puts maximum flux on center leg.


If connected in parallel, it's a mess.

Not sure why if equal turns and opposing.
Might look into this, lowers operating voltage by 1/2.


Operating independantly, it's a can of worms.

No need to explore that.

Mikek


RL

With the same number of turns, you should read ~ same L value.

Series opposing should indicate a leakage inductance.

RL

 

[amdx]

On 9/11/2019 7:40 PM, legg wrote:

On Wed, 11 Sep 2019 15:34:21 -0500, amdx <nojunk@knology.net> wrote:

On 9/11/2019 9:17 AM, legg wrote:
On Tue, 10 Sep 2019 09:43:22 -0700 (PDT), amdx62@gmail.com wrote:

snip> Mikek

I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in the outer legs, the gap is just like a high value parallel resistor adding the the flux, but not much. To bring the gap into the picture I need to connect the two coils series opposing.
Mikek

If connected in series, the center core leg will be invisible.

It will be connected series opposing with equal turns on each leg.
This puts maximum flux on center leg.


If connected in parallel, it's a mess.

Not sure why if equal turns and opposing.
Might look into this, lowers operating voltage by 1/2.


Operating independantly, it's a can of worms.

No need to explore that.

Mikek


RL

With the same number of turns, you should read ~ same L value.

Agreed, I don't know how I got that wrong by 50 turns, I'm setting up a
counter for the next time. I have a couple of nice Veeder-Root counters.

Series opposing should indicate a leakage inductance.

I have no knowledge to support that.

I have about 100 turns on each leg.
L1 = 29.47mH
L2 = 29.47mH
L1//L2 = 28.69mH Parallel
L1\\L2 = 745.9uH Microhenries antiparallel
L1+L2 = 114.7mH114.7mH Series
L1-L2 = 2.982mH Anti-series

Large gap in center leg of E core.

Mikek

 

[legg]

On Thu, 12 Sep 2019 10:39:54 -0500, amdx <nojunk@knology.net> wrote:

On 9/11/2019 7:40 PM, legg wrote:
On Wed, 11 Sep 2019 15:34:21 -0500, amdx <nojunk@knology.net> wrote:

On 9/11/2019 9:17 AM, legg wrote:
On Tue, 10 Sep 2019 09:43:22 -0700 (PDT), amdx62@gmail.com wrote:

snip> Mikek

I think I just solved my dilemma.
I have a large E core with a wide gap, I have two windings, put on the outer legs, one winding is 401mH, other 528mH, series aiding 1819mH.
My thinking is in series aiding the magnetic flux is circulating mostly in the outer legs, the gap is just like a high value parallel resistor adding the the flux, but not much. To bring the gap into the picture I need to connect the two coils series opposing.
Mikek

If connected in series, the center core leg will be invisible.

It will be connected series opposing with equal turns on each leg.
This puts maximum flux on center leg.


If connected in parallel, it's a mess.

Not sure why if equal turns and opposing.
Might look into this, lowers operating voltage by 1/2.


Operating independantly, it's a can of worms.

No need to explore that.

Mikek


RL

With the same number of turns, you should read ~ same L value.

Agreed, I don't know how I got that wrong by 50 turns, I'm setting up a
counter for the next time. I have a couple of nice Veeder-Root counters.


Series opposing should indicate a leakage inductance.

I have no knowledge to support that.

I have about 100 turns on each leg.
L1 = 29.47mH
L2 = 29.47mH
L1//L2 = 28.69mH Parallel
L1\\L2 = 745.9uH Microhenries antiparallel
L1+L2 = 114.7mH114.7mH Series
L1-L2 = 2.982mH Anti-series

Large gap in center leg of E core.

Mikek

Try measuring the inductance of one, with the other shorted and
compare this to your list of measurements. It will closely resemble
one of them.

RL