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

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I want to create an inductor with a ferrite core of 2.2 mH, but I do not know the size of the core, the number of turns and the size of the wire. The maximum voltage and current of my work are 429 volts and 2 amps respectively .
Thank you for introducing a document or book on the design of an inductor with a ferrite toroid core. Thanks for helping me.

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Monday, July 1, 2019 at 12:31:05 PM UTC+2, snipped-for-privacy@gmail.com wrote:

know the size of the core, the number of turns and the size of the wire. Th
e maximum voltage and current of my work are 429 volts and 2 amps respectiv
ely .

with a ferrite toroid core. Thanks for helping me.

https://www.tdk-electronics.tdk.com/en/180386/tech-library/publications/fer
rites/ferrites-and-accessories-/519702

might be a good place to start.

Two amps through 2.2mH is storing 4.4mJ, which is a fair bit.

I've used RM14 cores for this sort of work.

https://www.tme.eu/Document/2b0ab2738d00530fe54723f5644cd416/rm_14.pdf

On the most heavily gapped core you'd need 117 turns to get 2.2mH which is
234 Ampere turns. The magnetic path length is about 1.9mm - the path throug
h the cores is longer, but gets divided by the permeability of the core whi
ch is about a thousand-odd - so you get to 123 Ampere.turns per metre (whic
h if memory serves won't saturate the ferrite -  but don't rely on my memor
y).

You've only got 0.58 mm^2 of wire area to carry your 2 amps, which might no
t be enough. The coils could get too warm - and if the ferrite gets warmer
than it's Curie temperature, it stops being ferromagnetic at all.

You might well need a bigger core pair, which you would probably have to ga
p yourself. Don't use metal shim!

The EPCOS application notes detailed this kind of calculation in more detai
l, with lots of helpful tables, but you need to go through them yourelf.

The 479 volts is on the high side - enamelled wire is rated for 500V and do
uble enamelled wire - which is freely available - it a little better.

The voltage between layers of wire will be less than the full 479 volts,and
you'd need six layers of wire to fit 117 turns on an RM14 former, so that
wouldn't be a problem but you might want to sleeve the wires after they com
e off the coil.

--
Bill Sloman, Sydney

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Monday, 1 July 2019 12:31:05 UTC+2, snipped-for-privacy@gmail.com  wrote:

A standard ferrite will be better since toroid with distributed airgap typically has significantly higher core losses

Cheers

Klaus

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Mon, 1 Jul 2019 05:51:55 -0700 (PDT), snipped-for-privacy@gmail.com
wrote:

Unfortunately, magnetics design is complex. The problem is, given the
above, under-defined.

That depends on the magnitude and frequency of the AC excitation,
which isn't stated. The "cool-mu" and equivalent mix toroids are
powdered iron.

One trick to short-cut design is to find a catalog part that looks
like it will work, and basically copy it. It will at least get you a
starting point.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

Re: How to create an inductor 2.mH with a toroid core ferrite?
John Larkin wrote...

Another trick is to find a catalog part that looks like

--
Thanks,
- Win

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

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.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

Re: How to create an inductor 2.mH with a toroid core ferrite?
John Larkin wrote...

It looks machine made.  Why was it better?

--
Thanks,
- Win

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

I'm the machine! My mechanical guy is working on a proper mandrel.

The first two gens were Coilcraft parts, superficially in spec. Both
got way too hot as the pulse rate went up; this is a kilovolt, 5 MHz
pulse generator. The revB flat things should have worked, but their
cooling is bad and there must be some proximity effect increasing skin
losses. The hand-wound thing has spacing to reduce proximity and to
let some air in, fat wire for more skin, and is conduction cooled,

Everything gets hot on this board, being pulsed this hard. Traces. Fr4
laminate. Capacitors. Even the output barrier strip got hot from
dielectric loss.

There will be a rev D.

"This power magnetics stuff is hard."

--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

We've slightly trimmed the long signature. Click to see the full one.
Re: How to create an inductor 2.mH with a toroid core ferrite?
John Larkin wrote...

I got my 50-ohm kV pulse-picker to work to 5MHz, but
my goal was 10MHz.  Solved that by interleaving two
of them at 5MHz each.  Maybe that would work for you.

--
Thanks,
- Win

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

Actually, that would. I could sell twice as many! I'll mention that to
the customer. My circuit seems to be hitting fundamental limits around
5M and 1KV, and it gets worse as V^2, or actually something worse than
V^2. We need better fets.

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

--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

We've slightly trimmed the long signature. Click to see the full one.
Re: How to create an inductor 2.mH with a toroid core ferrite?
John Larkin wrote...

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

--
Thanks,
- Win

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Monday, July 1, 2019 at 10:45:39 AM UTC-7, John Larkin wrote:

Yeah, the design rules are coupled interacting equations, and some of the
limits (due to nonlinearities) are 'soft'.   Magnetic materials have a LOT of tabulated
data that needs consideration.    Other characteristics are
geometry-dependent and mechanics gets  involved, too.

I tried a design once, after looking at a reference design: I couldn't figure out
why they used such a large core (about five times the mass required), and I had
a stash of surplus cores (twice the required mass, but higher frequency)... after
some calculating (couple of pages, all told, of algebra and notes) I shrugged and
wound some; for my signals, it all worked fine.

Later commercial designs DIDN'T use the oversize cores, were more elegant
than my (clunky from surplus parts) units.   I'll never know why the originals were
so oversized.     The 'look at an example' plan was not a good start.

Re: How to create an inductor 2.mH with a toroid core ferrite?
On a sunny day (Mon, 01 Jul 2019 08:47:41 -0700) it happened John Larkin

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?

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

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/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.

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Mon, 01 Jul 2019 17:03:50 GMT, Jan Panteltje

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.

Make me.

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

--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

We've slightly trimmed the long signature. Click to see the full one.
Re: How to create an inductor 2.mH with a toroid core ferrite?
On a sunny day (Mon, 01 Jul 2019 10:46:40 -0700) it happened John Larkin

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.

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.

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

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Mon, 01 Jul 2019 18:19:19 GMT, Jan Panteltje

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.

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.

--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

We've slightly trimmed the long signature. Click to see the full one.
Re: How to create an inductor 2.mH with a toroid core ferrite?
mandag den 1. juli 2019 kl. 21.18.59 UTC+2 skrev John Larkin:

small smd parts is the exception, for heavy parts and many connectors
the rule still holds

Re: How to create an inductor 2.mH with a toroid core ferrite?
On Monday, July 1, 2019 at 9:18:59 PM UTC+2, John Larkin wrote:

d
_5179.JPG
o_it_IMG_6111.JPG

vered

And silvered copper wire tends to be electroplated, and electroplated silve
r is less conductive than bulk silver. You could probably flash heat the el
ectroplated layer with a fast power laser, and melt the silver layer withou
t letting it alloy with the copper. Using silver-plated wire for RF coils i
s a ham tradition, but serious engineers haven't bother for decades now.

ers

But ham-handed operators are unavoidable.

--
Bill Sloman, Sydney

Re: How to create an inductor 2.mH with a toroid core ferrite?
On 2/7/19 5:15 am, John Larkin wrote:

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.

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

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

We've slightly trimmed the long signature. Click to see the full one.