Author Topic: Toroids, magnet wire and Inductors, oh my! -- Sources and resources.  (Read 2173 times)

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Offline Jebnor

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Where does one source inexpensive(ish) toroids, magnet wire, power inductors and the like?  Non-cheap sources would also be nice. The usual haunts for cheap chinese stuff tend not to have any components which require magnetic flux of any sort. And I can't seem to find any retailers who have more than mish-mash of 'leftovers'.

In the end, I'd like to know where I can get parts to make my own transformers, inductors and chokes, both power and signal.

Any old school primers on transformer design would be fantastic too.

Regads,
Jebnor
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Offline T3sl4co1l

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Re: Toroids, magnet wire and Inductors, oh my! -- Sources and resources.
« Reply #1 on: August 25, 2014, 10:33:25 pm »
Online ordering:
Mouser: EPCOS/TDK cores and bobbins are fairly well stocked, considering.  Also Fair-Rite, and the usual EMI parts (beads / snap-its / plates / etc.) from Steward, Laird, etc.
Amidon: relatively expensive; powdered iron toroids and various shapes of ferrites.

Online inventory, quoting:
Elna Magnetics
Adams Magnetic

I don't know of any supplier with searchable / selectable core parameters, so you'll have to check back and forth between manufacturers' catalogs and supplier inventories to select parts.  PITA, but I guess the magnetics business goes so slowly that they have little need of modern computerized interfaces (one of those "be thankful they're even on the internet" things).

Manufacturers (you can usually guess from the types or codes who it is; Amidon doesn't list manufacturers on their up-front catalog):
Micrometals (powdered iron)
Arnold Magnetics, Magnetics Inc. (Sendust, MPP, etc. powder cores)
Magnetics Inc. (also stripwound cores, ferrites)
Fair-Rite (ferrites...if you can imagine)
Ferroxcube (ferrites, powder cores)
EPCOS/TDK (ferrites usually, I think other stuff too though)
And probably a bunch of others I can't think of at the moment.

My documentation: rather old, though. http://seventransistorlabs.com/tmoranwms/Elec_Magnetics.html

Never really finished the inductor section; I know better now.  Works the same as with transformers, select core area based on turns and flux.  Flux is amps * inductance (since inductance is Wb/A), and that's peak flux for whatever peak current you apply.  Once you have enough flux, you can set the inductance anywhere you want by adjusting the air gap, which means you get flux first, then tune for the amps required.  Don't worry too much about energy or energy density.  You'll be in the right range when you find a core that ends up with a calculated gap that produces an effective permeability of 20-100.

Also, mind that the winding will generally benefit from using Litz wire, even if the wire is significantly smaller than the (free air) skin effect at the frequency you're using it at.  Reason being, for each and every layer in the winding, proximity effect squeezes the current tighter and tighter, easily 2-10 times tighter than skin effect alone would suggest.  You have some gain already from using just a few strands in parallel (multifilar), and from using >20 strands (usually as proper Litz), you can recover all the cross-sectional area of the copper you started with (the winding factor of Litz is lower, but more than made up by the efficiency gain).  This assumes you're using a ferrite core because you need low losses -- if you're just smoothing DC, use powdered iron.  (And, to select powdered iron, you don't usually get gapping as an option, so choose a grade based on losses, then select a size and calculate turns.  Don't worry so much about using multiple strands, as you'll usually be seeing more core than copper loss, even with moderate levels of ripple.)

Tim
« Last Edit: August 25, 2014, 10:37:25 pm by T3sl4co1l »
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Offline nanofrog

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Re: Toroids, magnet wire and Inductors, oh my! -- Sources and resources.
« Reply #2 on: August 25, 2014, 10:37:38 pm »
Where does one source inexpensive(ish) toroids, magnet wire, power inductors and the like?  Non-cheap sources would also be nice. The usual haunts for cheap chinese stuff tend not to have any components which require magnetic flux of any sort. And I can't seem to find any retailers who have more than mish-mash of 'leftovers'.

In the end, I'd like to know where I can get parts to make my own transformers, inductors and chokes, both power and signal.
Perhaps these might help (by no means all-inclusive).

Alpha Core / Bridgeport Magnetics Toroid supplies
Thomas and Skinner Transformer Laminations
Foremost Plastic Products Bobbins
Lodestone Pacific Bobbins & Tapes

Any old school primers on transformer design would be fantastic too.
Practical Transformer Winding
 

Offline IanB

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Re: Toroids, magnet wire and Inductors, oh my! -- Sources and resources.
« Reply #3 on: August 26, 2014, 12:28:21 am »
I have never used them, but this company looks like a nice one to have in your bookmarks:

http://palomar-engineers.com/

Magnetic cores of all kinds and general data with an emphasis on ham radio applications.
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Offline w2aew

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Re: Toroids, magnet wire and Inductors, oh my! -- Sources and resources.
« Reply #4 on: August 26, 2014, 01:56:46 am »
For toroids, wire, and other parts for RF applications, you might want to check out:
http://www.kitsandparts.com/toroids.php
YouTube channel: https://www.youtube.com/w2aew
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Offline Jebnor

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Re: Toroids, magnet wire and Inductors, oh my! -- Sources and resources.
« Reply #5 on: August 26, 2014, 03:53:44 pm »
Thanks everyone, on to research.
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