I am trying to make some high value toroids, about 1mH. I have a commercial
one using a half inch core with about 20turns on it to give 3.3mH. Does
anyone know what the core material/description is or an UK source please?
The normal ones such as T37-2s etc only give a few uH.

Thanks

Graham

On Fri, 23 Jan 2004 14:13:09 -0000, "Graham"
wrote:

I am trying to make some high value toroids, about 1mH. I have a commercial
one using a half inch core with about 20turns on it to give 3.3mH. Does
anyone know what the core material/description is or an UK source please?
The normal ones such as T37-2s etc only give a few uH.

I got some from Bardwells that were about 20mm dia and when
close-wound all round with one layer of 0.7mm enamel wire came out at
exactly 1mH (which was handy since that was the objective!). Give them
a try. They do mail order and are very reasonable.
--

My opinion is worth what you've paid for it.

Graham wrote:

I am trying to make some high value toroids, about 1mH. I have a commercial
one using a half inch core with about 20turns on it to give 3.3mH. Does
anyone know what the core material/description is or an UK source please?
The normal ones such as T37-2s etc only give a few uH.

Thanks

Graham

There are two basic categories of toroid cores. Those that contain
distributed gaps between bits or sections of high permeability
material (to increase their energy storage capability) and those made
with a single material that has a high permeability (may be metal,
metal tape or ferrite ceramic).

The T series are the distributed gap type. Their claim to fame is
their ability to have stable inductance with high ampere turns
applied. So before you can choose a core material, you not only have
to specify the inductance required, but the ampere turns this
inductance must support.

Here are links to a few ferrite manufacturers:
http://www.fair-rite.com/
http://www.mag-inc.com/ (also makes the powdered iron cores)
http://www.neosid.com/fercor/toroids/tormn.htm
http://www.ferroxcube.com/prod/assets/fertor.htm
http://tciceramics.com/f_toroid.htm

Many others are available through Google. The first link includes an
inductor design tutorial at the back of their catalog that may be
helpful.

--
John Popelish

These are ferrite, the other type is iron powder.
I found this site useful for unknown cores.


http://www.alan.melia.btinternet.co.uk/toroids.htm



"Graham" wrote in
:

I am trying to make some high value toroids, about 1mH. I have a
commercial one using a half inch core with about 20turns on it to give
3.3mH. Does anyone know what the core material/description is or an UK
source please? The normal ones such as T37-2s etc only give a few uH.

Thanks

Graham

On Fri, 23 Jan 2004 15:48:13 +0000, Paul Burridge
wrote:

On Fri, 23 Jan 2004 14:13:09 -0000, "Graham"
wrote:

I am trying to make some high value toroids, about 1mH. I have a commercial
one using a half inch core with about 20turns on it to give 3.3mH. Does
anyone know what the core material/description is or an UK source please?
The normal ones such as T37-2s etc only give a few uH.

I got some from Bardwells that were about 20mm dia and when
close-wound all round with one layer of 0.7mm enamel wire came out at
exactly 1mH (which was handy since that was the objective!). Give them
a try. They do mail order and are very reasonable.
--

My opinion is worth what you've paid for it.

my conclusion worth a penny is that it depends on whether you are
building a transformer or inductor, in the first place the core you
refer to may be good for a transformer, but suppose it is useless for
most applications as an inductor

73
LA8AK
--
Amount of SPAM is so large that MailWasher must delete 99% of the incoming mails
Cannot check every email manually. Please use intelligent title for email.
Mails without titles or using just "hi" is deleted

On Fri, 23 Jan 2004 23:40:21 GMT (J M Noeding) wrote:

On Fri, 23 Jan 2004 15:48:13 +0000, Paul Burridge
wrote:

On Fri, 23 Jan 2004 14:13:09 -0000, "Graham"
wrote:

I am trying to make some high value toroids, about 1mH. I have a commercial
one using a half inch core with about 20turns on it to give 3.3mH. Does
anyone know what the core material/description is or an UK source please?
The normal ones such as T37-2s etc only give a few uH.

I got some from Bardwells that were about 20mm dia and when
close-wound all round with one layer of 0.7mm enamel wire came out at
exactly 1mH (which was handy since that was the objective!). Give them
a try. They do mail order and are very reasonable.

my conclusion worth a penny is that it depends on whether you are
building a transformer or inductor, in the first place the core you
refer to may be good for a transformer, but suppose it is useless for
most applications as an inductor

As long as you're talking about an inductor or a transformer operating
at the same frequency, I think any core material that works well for
one will work well for the other.

What the best core material might be for a particular application
depends heavily on the operating frequency.

For the original poster, you might want to look into powdered iron
toroids, assuming your frequency is not too high.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
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