How to create an inductor 2.mH with a toroid core ferrite?

[Bill Sloman]

On Monday, July 1, 2019 at 9:18:59 PM UTC+2, John Larkin wrote:

On Mon, 01 Jul 2019 18:19:19 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Mon, 01 Jul 2019 10:46:40 -0700) it happened John Larkin
jjlarkin@highland_snip_technology.com> wrote in
sfhkhe1f7mgd4sfl9ge7dn32gc1ll8jlo9@4ax.com>:

On Mon, 01 Jul 2019 17:03:50 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

https://www.dropbox.com/s/lmkj7tavf2ou77t/L1C.JPG?raw=1


The first two looked fine according to data sheets, but then I learned
a lot about skin effect. And customer spec-ratcheting.

RevC is hand-wound on a custom mandrel (aka Sharpie Pen) and
air+conduction cooled.

That third link looks mechanical feeble
if it gets hot it will unsolder itself,
and if there is a lot of vibration it will unsolder itself too,
maybe even pull the tracks of the board,
is that bare copper end protected by sone stuff?

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.


There is a spec that says the wire should go through the hole etc etc,
but that was mil long ago, maybe it changed

Make me.

Been a long time ago I designed for navy and army,
but they were VERY precise in these things,.,,
Always days of acceptance testing in some lab.

I've designed flight hardware for the Air Force and for NASA, but it's
10% design and 390% compliance nonsense. I don't want to do any more
of that.

It was long lore that solder should never be used as mechanical
support, until Tektronix broke that rule. And now we have surface
mount.



Transformers are easy once you get the hang of it
http://panteltje.com/pub/ultrasonic_antifouling_bigger_transformer_IMG_5179.JPG
http://panteltje.com/pub/home_made_1_to_33_hv_transformer_img_3096.jpg
http://panteltje.com/pub/12V_to_300Vpp_converter_detail_all_there_is_to_it_IMG_6111.JPG
http://panteltje.com/pub/new_transformer_test_setup_img_3153.jpg

I have a box full of various sizes Ecores, and some ring cores...
You can get good ringcores from old PC power supplies.

Al, type of ferrite, L, number of turns.... power, saturation,
OP will have to give a ciruit and more details.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

What I wondered is as you talk about skin effect why do you not used silvered
wire? I use silvered wire for all RF coils.

Silver only conducts a bit better than copper.

And silvered copper wire tends to be electroplated, and electroplated silver is less conductive than bulk silver. You could probably flash heat the electroplated layer with a fast power laser, and melt the silver layer without letting it alloy with the copper. Using silver-plated wire for RF coils is a ham tradition, but serious engineers haven't bother for decades now.

I'm using #14 copper
magnet wire, from Amazon Prime. Given skin effect, most of my copper
is not being used. My skin depth is very roughly 10 microns. Litz is
apparently not useful up in the MHz range.

Several smaller inductors in parallel would theoretically use the
copper better, but this beast works.

As to coil formers, in the old days for example I used ceramic coil formers
with a thread cut in it where the silvered wire was to sit, so it could not move about.
I mean like this:
http://www.hamtech.hu/coil_body.html

We're making a winding mandrel, but the actual coil will be
freestanding, like in the pic.

This pulser gets bolted to an optical bench in a big heavy laser. I
don't expect vibration.

But ham-handed operators are unavoidable.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Monday, July 1, 2019 at 7:50:12 PM UTC+2, John Larkin wrote:

On Mon, 01 Jul 2019 17:03:50 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Mon, 01 Jul 2019 08:47:41 -0700) it happened John Larkin
jjlarkin@highlandtechnology.com> wrote in
aj9khe1b2r75gcddlh0jqg707uvcaig0hk@4ax.com>:

On 1 Jul 2019 08:11:07 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

John Larkin wrote...

One trick to short-cut design is to find a catalog part
that looks like it will work, and basically copy it.

Another trick is to find a catalog part that looks like
it will work, and buy it. Find and buy several types.

I always prefer to buy magnetics instead of building them. An existing
part could get one into the ballpark on size and weight for a custom
design

Here are *three* generations of inductors.

https://www.dropbox.com/s/ml9ay639wdmbwrz/L1A.jpg?raw=1

https://www.dropbox.com/s/wmhkgdg6v52mxxe/L1B.JPG?raw=1

https://www.dropbox.com/s/lmkj7tavf2ou77t/L1C.JPG?raw=1


The first two looked fine according to data sheets, but then I learned
a lot about skin effect. And customer spec-ratcheting.

RevC is hand-wound on a custom mandrel (aka Sharpie Pen) and
air+conduction cooled.

That third link looks mechanical feeble
if it gets hot it will unsolder itself,
and if there is a lot of vibration it will unsolder itself too,
maybe even pull the tracks of the board,
is that bare copper end protected by sone stuff?

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.


There is a spec that says the wire should go through the hole etc etc,
but that was mil long ago, maybe it changed

Make me.



Transformers are easy once you get the hang of it
http://panteltje.com/pub/ultrasonic_antifouling_bigger_transformer_IMG_5179.JPG
http://panteltje.com/pub/home_made_1_to_33_hv_transformer_img_3096.jpg
http://panteltje.com/pub/12V_to_300Vpp_converter_detail_all_there_is_to_it_IMG_6111.JPG
http://panteltje.com/pub/new_transformer_test_setup_img_3153.jpg

I have a box full of various sizes Ecores, and some ring cores...
You can get good ringcores from old PC power supplies.

Al, type of ferrite, L, number of turns.... power, saturation,
OP will have to give a ciruit and more details.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

You should have looked at a nickel-zinc ferrite core. Nothing else is resistive enough to work with a 5MHz pulse stream - the pulses have harmonic content up from 5MHz to an upper limit set by the pulse width.

They don't offer particulary high permeabilities, but you don't tend to need much at those sorts of frequencies.

--
Bill Sloman, Sydney

 

[whit3rd]

On Monday, July 1, 2019 at 10:50:12 AM UTC-7, John Larkin wrote:

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

It's not unheard-of to heatsink a transformer. Thru-bolt attach
to a pot core, or package in a cast or extruded aluminum box with potting
compound.

On the large side, pole pig transformers have an oil bath and pipe
for radiator surfaces.

 

[John Larkin]

On Mon, 1 Jul 2019 13:52:08 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Monday, July 1, 2019 at 10:50:12 AM UTC-7, John Larkin wrote:

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

It's not unheard-of to heatsink a transformer.

This inductor is heat sunk. It needs to be.

Thru-bolt attach
to a pot core, or package in a cast or extruded aluminum box with potting
compound.

Pot cores are usually electrically conductive. I have 1200 volts here.

Potting is a mess.

I can wind this coil in one minute. It works fine.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[John Larkin]

On Tue, 2 Jul 2019 09:00:25 +1000, Clifford Heath <no.spam@please.net>
wrote:

On 2/7/19 5:15 am, John Larkin wrote:
On Mon, 01 Jul 2019 18:19:19 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
What I wondered is as you talk about skin effect why do you not used silvered wire?
I use silvered wire for all RF coils.

Silver only conducts a bit better than copper. I'm using #14 copper
magnet wire, from Amazon Prime. Given skin effect, most of my copper
is not being used. My skin depth is very roughly 10 microns. Litz is
apparently not useful up in the MHz range.

Several smaller inductors in parallel would theoretically use the
copper better, but this beast works.

We're making a winding mandrel, but the actual coil will be
freestanding, like in the pic.

This pulser gets bolted to an optical bench in a big heavy laser. I
don't expect vibration.

Magnetostriction will create vibration. 5MHz means the amplitude won't
be much, but the fracture mechanics depend on energy levels, not just
amplitude.

What's the objection to dropping a 90 degree angle through the board at
each end of the coil?

Clifford Heath.

1200 volt, 7 ns pulses arcing to the water-cooled plate 50 mils below
the PCB.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[Winfield Hill]

John Larkin wrote...

Mode-locked lasers typically run around 80 MHz,
so a 10M picker selects every 8th pulse.

Some applications let you select two pulses next
to each other, etc. A duty-cycle kind of thing.


--
Thanks,
- Win

 

[Clifford Heath]

On 2/7/19 5:15 am, John Larkin wrote:

On Mon, 01 Jul 2019 18:19:19 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
What I wondered is as you talk about skin effect why do you not used silvered wire?
I use silvered wire for all RF coils.

Silver only conducts a bit better than copper. I'm using #14 copper
magnet wire, from Amazon Prime. Given skin effect, most of my copper
is not being used. My skin depth is very roughly 10 microns. Litz is
apparently not useful up in the MHz range.

Several smaller inductors in parallel would theoretically use the
copper better, but this beast works.

We're making a winding mandrel, but the actual coil will be
freestanding, like in the pic.

This pulser gets bolted to an optical bench in a big heavy laser. I
don't expect vibration.

Magnetostriction will create vibration. 5MHz means the amplitude won't
be much, but the fracture mechanics depend on energy levels, not just
amplitude.

What's the objection to dropping a 90 degree angle through the board at
each end of the coil?

Clifford Heath.

 

[Winfield Hill]

John Larkin wrote...

This inductor is heat sunk. It needs to be.
... I have 1200 volts here.

What is that, a 1.2kV flyback inductor?


--
Thanks,
- Win

 

[John Larkin]

On 1 Jul 2019 16:38:09 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

John Larkin wrote...

This inductor is heat sunk. It needs to be.
... I have 1200 volts here.

What is that, a 1.2kV flyback inductor?

Top secret, but sort of a matching network that I didn't expect to get
hot. Designed by Spice fiddling, so I barely understand how it works.






--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[Clifford Heath]

On 2/7/19 9:17 am, John Larkin wrote:

On Tue, 2 Jul 2019 09:00:25 +1000, Clifford Heath <no.spam@please.net
wrote:

On 2/7/19 5:15 am, John Larkin wrote:
On Mon, 01 Jul 2019 18:19:19 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
What I wondered is as you talk about skin effect why do you not used silvered wire?
I use silvered wire for all RF coils.

Silver only conducts a bit better than copper. I'm using #14 copper
magnet wire, from Amazon Prime. Given skin effect, most of my copper
is not being used. My skin depth is very roughly 10 microns. Litz is
apparently not useful up in the MHz range.

Several smaller inductors in parallel would theoretically use the
copper better, but this beast works.

We're making a winding mandrel, but the actual coil will be
freestanding, like in the pic.

This pulser gets bolted to an optical bench in a big heavy laser. I
don't expect vibration.

Magnetostriction will create vibration. 5MHz means the amplitude won't
be much, but the fracture mechanics depend on energy levels, not just
amplitude.

What's the objection to dropping a 90 degree angle through the board at
each end of the coil?

Clifford Heath.

1200 volt, 7 ns pulses arcing to the water-cooled plate 50 mils below
the PCB.

Ah, I can see that would be a problem.

Well, just make sure the solder fillet radius is big enough to relieve
the stress riser, and test it.

Clifford Heath.

 

[Jan Panteltje]

On a sunny day (Mon, 01 Jul 2019 16:20:57 -0700) it happened John Larkin
<jjlarkin@highland_snip_technology.com> wrote in
<f55lhepdr82bg30lmmcc2vjbfcrf28jg4c@4ax.com>:

On Mon, 1 Jul 2019 13:52:08 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Monday, July 1, 2019 at 10:50:12 AM UTC-7, John Larkin wrote:

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

It's not unheard-of to heatsink a transformer.

This inductor is heat sunk. It needs to be.

Thru-bolt attach
to a pot core, or package in a cast or extruded aluminum box with potting
compound.

Pot cores are usually electrically conductive. I have 1200 volts here.

Potting is a mess.

I can wind this coil in one minute. It works fine.

Ceramic coil formers do make heatsinks,
and if mounted vertical can be made mechanical rigid.
You could tap into the heatsink for mounting. that would draw away heat from the ceramic.
The coil top connection lead length would add some inductance,
matter of testings if it works.
Or mount the ceramic former horizontal with brackets screwed into the heatsink below,
some epoxy perhaps.

No thermal foam under the coil needed...

I have used those ceramic coil formers with tubes, class B output linear
with 500 V anode voltage (~1 kVpp) 250 W CW, about 7 MHz, mounted on a steel plate,

 

[Bill Sloman]

On Tuesday, July 2, 2019 at 1:24:29 AM UTC+2, John Larkin wrote:

On Mon, 1 Jul 2019 13:52:08 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Monday, July 1, 2019 at 10:50:12 AM UTC-7, John Larkin wrote:

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

It's not unheard-of to heatsink a transformer.

This inductor is heat sunk. It needs to be.

Thru-bolt attach
to a pot core, or package in a cast or extruded aluminum box with potting
compound.

Pot cores are usually electrically conductive. I have 1200 volts here.

Nickel Zinc ferrites are less conductive than the regular managanese zinc ferrites, which is why they remain useful up to hgiher frequencies.

> Potting is a mess.

So is designing magnetic components so that they will do the job you need to be done.

Tinkering creates a different kind of mess.

> I can wind this coil in one minute. It works fine.

But gets hot, and is vulnerable to mechanical deformation.

Fewer turns around a nickel zinc ferrite core might less you use heavier wire and the assembly - including the ferrite - might dissipate less heat and might be more compact. You'd have to find your nickel zinc ferrite cores, which might take some work - they weren't high volume items when I last looked at them, which was a while ago.

--
Bill Sloman,

 

[Winfield Hill]

John Larkin wrote...

On 1 Jul 2019, Winfield Hill wrote:
John Larkin wrote...

This inductor is heat sunk. It needs to be.
... I have 1200 volts here.

What is that, a 1.2kV flyback inductor?

Top secret, but sort of a matching network that
I didn't expect to get hot. Designed by Spice
fiddling, so I barely understand how it works.

Series-resonance peaking. Sneaky.


--
Thanks,
- Win

 

[Bill Sloman]

On Tuesday, July 2, 2019 at 12:18:14 PM UTC+2, Winfield Hill wrote:

John Larkin wrote...

On 1 Jul 2019, Winfield Hill wrote:
John Larkin wrote...

This inductor is heat sunk. It needs to be.
... I have 1200 volts here.

What is that, a 1.2kV flyback inductor?

Top secret, but sort of a matching network that
I didn't expect to get hot. Designed by Spice
fiddling, so I barely understand how it works.

Series-resonance peaking. Sneaky.

But not exactly top secret. John Larkin does re-invent the wheel a little too frequently for somebody who claims to do electronic design.

--
Bill Sloman, Sydney

 

[John Larkin]

On 2 Jul 2019 10:28:04 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

John Larkin wrote...

The gap-pad stuff isn't bad in production.
It seriously drops the coil temperature.

Which p/n of gap pad are you using?

TW-T600-2MM from 3G Shielding. It's rated 6 W/mK, which it actually
does if compressed pretty good.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[Winfield Hill]

John Larkin wrote...

The gap-pad stuff isn't bad in production.
It seriously drops the coil temperature.

Which p/n of gap pad are you using?


--
Thanks,
- Win

 

[John Larkin]

On Tue, 02 Jul 2019 05:49:26 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Mon, 01 Jul 2019 16:20:57 -0700) it happened John Larkin
jjlarkin@highland_snip_technology.com> wrote in
f55lhepdr82bg30lmmcc2vjbfcrf28jg4c@4ax.com>:

On Mon, 1 Jul 2019 13:52:08 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Monday, July 1, 2019 at 10:50:12 AM UTC-7, John Larkin wrote:

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

It's not unheard-of to heatsink a transformer.

This inductor is heat sunk. It needs to be.

Thru-bolt attach
to a pot core, or package in a cast or extruded aluminum box with potting
compound.

Pot cores are usually electrically conductive. I have 1200 volts here.

Potting is a mess.

I can wind this coil in one minute. It works fine.

Ceramic coil formers do make heatsinks,
and if mounted vertical can be made mechanical rigid.
You could tap into the heatsink for mounting. that would draw away heat from the ceramic.
The coil top connection lead length would add some inductance,
matter of testings if it works.
Or mount the ceramic former horizontal with brackets screwed into the heatsink below,
some epoxy perhaps.

No thermal foam under the coil needed...

I have used those ceramic coil formers with tubes, class B output linear
with 500 V anode voltage (~1 kVpp) 250 W CW, about 7 MHz, mounted on a steel plate,

The coil could be wound tight on an alumina or AlN rod, which would
spread out the heat some. A machined spiral groove would be ideal, but
hard to fabricate.

The gap-pad stuff isn't bad in production. It seriously drops the coil
temperature.

Epoxy is always messy, so we try to avoid that.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[John Larkin]

On 2 Jul 2019 03:17:53 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

John Larkin wrote...

On 1 Jul 2019, Winfield Hill wrote:
John Larkin wrote...

This inductor is heat sunk. It needs to be.
... I have 1200 volts here.

What is that, a 1.2kV flyback inductor?

Top secret, but sort of a matching network that
I didn't expect to get hot. Designed by Spice
fiddling, so I barely understand how it works.

Series-resonance peaking. Sneaky.

One think that's fun is to sort of randomly stick inductors into
circuits to see if they speed things up, to make exponential things
more critically damped. I'd like to get good with t-coils, but they
are harder to manufacture than just buying inductors.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[Bill Sloman]

On Tuesday, July 2, 2019 at 6:56:35 PM UTC+2, John Larkin wrote:

On Tue, 02 Jul 2019 05:49:26 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Mon, 01 Jul 2019 16:20:57 -0700) it happened John Larkin
jjlarkin@highland_snip_technology.com> wrote in
f55lhepdr82bg30lmmcc2vjbfcrf28jg4c@4ax.com>:

On Mon, 1 Jul 2019 13:52:08 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Monday, July 1, 2019 at 10:50:12 AM UTC-7, John Larkin wrote:

The whole idea is to keep it from getting too hot. Heat is bad. Copper
resistance goes up about 0.4% per deg C, which is practically thermal
runaway.

I considered a cored inductor here but nothing looked like it would
work. I'd burn the paint off a powdered iron toroid.

It's not unheard-of to heatsink a transformer.

This inductor is heat sunk. It needs to be.

Thru-bolt attach
to a pot core, or package in a cast or extruded aluminum box with potting
compound.

Pot cores are usually electrically conductive. I have 1200 volts here.

Potting is a mess.

I can wind this coil in one minute. It works fine.

Ceramic coil formers do make heatsinks,
and if mounted vertical can be made mechanical rigid.
You could tap into the heatsink for mounting. that would draw away heat from the ceramic.
The coil top connection lead length would add some inductance,
matter of testings if it works.
Or mount the ceramic former horizontal with brackets screwed into the heatsink below, some epoxy perhaps.

No thermal foam under the coil needed...

I have used those ceramic coil formers with tubes, class B output linear
with 500 V anode voltage (~1 kVpp) 250 W CW, about 7 MHz, mounted on a steel plate,

The coil could be wound tight on an alumina or AlN rod, which would
spread out the heat some. A machined spiral groove would be ideal, but
hard to fabricate.

Micro-cracked alumina is machinable. The trade name is MACOR.

https://www.pgo-online.com/intl/macor-machinable-glass-ceramic.html

It's thermal conductivity isn't great, but better than air.

The gap-pad stuff isn't bad in production. It seriously drops the coil
temperature.

Epoxy is always messy, so we try to avoid that.

"Messy" just means that you haven't worked out a way to do it tidily yet.

--
Bill Sloman, Sydney

 

[John Larkin]

On Tue, 2 Jul 2019 17:15:41 -0700 (PDT), pcdhobbs@gmail.com wrote:

W-T600-2MM from 3G Shielding.

I have their designer's kit, but they seem to have roughly zero distribution. Where do you buy it?

Cheers

Phil Hobbs

Directly from them.

The stuff is roughly $1 per square inch. Digikey has similar stuff.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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