How to design an Interesting inductor

A

amdx

Guest
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
 
On 8/19/2019 7:53 PM, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
 I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
 Is this possible?

               Thanks for your thoughts, Mikek
Click to expand...

If the "dc control winding has huge inductance", what difference does it
make? You will be applying DC.
 
On 8/19/2019 9:24 PM, John S wrote:
On 8/19/2019 7:53 PM, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

If the "dc control winding has huge inductance", what difference does it
make? You will be applying DC.
Click to expand...

I want to use the same winding that I'm using for the inductance.
This is my starting point, But I only want one winding,

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/radcom/2003/01/page78/index.html
Click to expand...


Mikek
 
On Mon, 19 Aug 2019 21:24:53 -0500, John S <Sophi.2@invalid.org>
wrote:

On 8/19/2019 7:53 PM, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
 I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
 Is this possible?

               Thanks for your thoughts, Mikek

If the "dc control winding has huge inductance", what difference does it
make? You will be applying DC.
Click to expand...

If they are wound on the same core, applying a voltage source to the
control winding shorts the signal. Applying a current source has its
own problems.

There are constructions where the mag fields are orthoginal, so the
control current doesn't link to the signal.

Mikek, why do you want a variable inductor?
 
On Mon, 19 Aug 2019 21:39:24 -0500, amdx <nojunk@knology.net> wrote:

On 8/19/2019 9:24 PM, John S wrote:
On 8/19/2019 7:53 PM, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

If the "dc control winding has huge inductance", what difference does it
make? You will be applying DC.

I want to use the same winding that I'm using for the inductance.
This is my starting point, But I only want one winding,

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/radcom/2003/01/page78/index.html



Mikek
Click to expand...

Given two separate ferrite-core inductors, you could put them in
parallel for AC and in series for DC. Then it's easy to inject the DC
control current without shorting the AC signal.

But why?
 
Why, how fast do you need to control it?

Tim

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

"amdx" <nojunk@knology.net> wrote in message
news:qjfga7$50i$1@dont-email.me...
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
Click to expand...
 
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Click to expand...

Use sufficient current, say more than 10 A to cause a sufficient
magnetic flux. In order to keep the voltage drop and hence power
dissipation down, thick wire is needed. This can be a problem
especially if Litz wire is used.

However, I do not understand how you are going to connect the DC
current into the LC? circuit since the DC power supply would be in
parallel with the inductance.

Is this possible?

Thanks for your thoughts, Mikek
Click to expand...
 
On 2019-08-20, amdx <nojunk@knology.net> wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?
Click to expand...

sounds like a magnetic amplifier, Q will probably be so-so.

--
When I tried casting out nines I made a hash of it.
 
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
 I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
 Is this possible?

               Thanks for your thoughts, Mikek
Click to expand...

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core

....this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar. I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers
--
Clive
 
On 8/20/2019 1:47 AM, Jasen Betts wrote:
On 2019-08-20, amdx <nojunk@knology.net> wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

sounds like a magnetic amplifier, Q will probably be so-so.
Click to expand...
In previous responses I gave the proposed use is for a
"Beverage on Ground" antenna.
I had a GOG before and used a beds that had a Q of 1 or 2.
so if I could get 20 it would be better.
Mikek
 
On Tue, 20 Aug 2019 03:33:18 -0500, amdx <nojunk@knology.net> wrote:

On 8/19/2019 9:49 PM, Tim Williams wrote:
Why, how fast do you need to control it?

Tim


Slow, in seconds.
Mikek
Click to expand...

How about a mechanical variometer.

Make a bar that fits into the coil. One end of the bar is made of some
ferrite material the other of aluminum. Connect it to a screw and run
it with a stepper motor.
 
tirsdag den 20. august 2019 kl. 15.57.08 UTC+2 skrev amdx:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers

Sorry, responses have made it clear I didn't ask my question well.
I only want one winding of 100uh, that winding will both the ac and
the dc.

Thanks, Mikek
Click to expand...

https://www.frostburg.edu/personal/latta/ee/qsk5/pindiodes/spstswitch.jpg

replace diode with your inductor and adjust values to match your freqency range
 
On 20/08/2019 14:57, amdx wrote:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to
full saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you
could wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound
on the bobbin, I don't know how many if wound through the hole, but
I'd guess it would be similar.  I'd try to grind the hole edges to
take off the sharp edge if possible.

Cheers

 Sorry, responses have made it clear I didn't ask my question well.
 I only want one winding of 100uh, that winding will both the ac and
the dc.

                           Thanks, Mikek
Click to expand...

OK, so the DC is from a high impedance current source I guess. As an
indication, a 100uH inductor on an RM4 3C92 core 722nH/T^2 will be 12
turns and saturate at around 500mA. There's a program, ferroxcube.exe
entitled Ferroxcube SFDT 2010 which is handy.

Cheers
--
Clive
 
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers
Click to expand...

Sorry, responses have made it clear I didn't ask my question well.
I only want one winding of 100uh, that winding will both the ac and
the dc.

Thanks, Mikek
 
On 8/20/2019 3:53 AM, upsidedown@downunder.com wrote:
On Tue, 20 Aug 2019 03:33:18 -0500, amdx <nojunk@knology.net> wrote:

On 8/19/2019 9:49 PM, Tim Williams wrote:
Why, how fast do you need to control it?

Tim


Slow, in seconds.
Mikek

How about a mechanical variometer.

Make a bar that fits into the coil. One end of the bar is made of some
ferrite material the other of aluminum. Connect it to a screw and run
it with a stepper motor.
Click to expand...

See later posts
Thanks, Mikek
 
On Tue, 20 Aug 2019 07:15:10 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

tirsdag den 20. august 2019 kl. 15.57.08 UTC+2 skrev amdx:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers

Sorry, responses have made it clear I didn't ask my question well.
I only want one winding of 100uh, that winding will both the ac and
the dc.

Thanks, Mikek

https://www.frostburg.edu/personal/latta/ee/qsk5/pindiodes/spstswitch.jpg

replace diode with your inductor and adjust values to match your freqency range
Click to expand...

One could also use PIN diodes, or relays, or latching relays to switch
taps on an air-core inductor, in interesting combinations. Q would be
high.
 
On 8/20/19 4:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers
Click to expand...

One minor tweak to that idea is to run an odd number of half-turns on
the bobbin, and use a high-mu pot core with an adjustable centre gap.

The extra half-turn will generate a large field going round the outside
of the core (avoiding the post) and so will saturate it fairly readily.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
Click to expand...
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL
 
"amdx" <nojunk@knology.net> wrote in message
news:qjgbfo$1la$1@dont-email.me...
In previous responses I gave the proposed use is for a
"Beverage on Ground" antenna.
I had a GOG before and used a beds that had a Q of 1 or 2.
so if I could get 20 it would be better.
Click to expand...

What power level? Frequency range?

Tim

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