Identifying Toroidial Inductor Cores

Hello

I recently got hold of about 20 cheap toroidial inductor cores that have clearly been taken from an old device, most likely an computer power supply, and I wish to identify them. I am particularly interested in whether they are Powdered Iron or Ferrite. There are too many to describe individually but I am wondering how I can identify them? Some are painted yellow and white or green and blue, some are grey, others are unpainted and grey or black and so on.

I have attempted to find out using google but have had no luck.

The only thing my search has turned up is that Powdered Iron cores conducts electricity, obviously, and ferrite does not. So maybe this means that the ferrites are unpainted and the powdered iron ones are painted to prevent them causing a short circuit?

Thanks

Hello,

It will be difficult to identify the types of cores.
One way could be an inductance measurement using a fixed number of turns on each core.
This way you can calculete the inductance index:
http://www.bytemark.com/products/sectwo.htm

You can also take a look at the sites of some large core supplying companies:
https://www.amidoncorp.com/
http://users.catchnet.com.au/~rjandusimports/

Bertus

Unless they have part numbers on them, you won't be able to tell what they are by color and size.

Check out this page:
http://www.dos4ever.com/flyback/flyback.html
Ronald Dekker's "Flyback Converters for Dummies" page is a great reference. If you don't have one yet, build his "Inductor Test Bench" about halfway down the page.

The "Mini Ring Core Calculator" is a very helpful free software tool for fiddling with toroidal inductors:
http://www.dl5swb.de/html/mini_ring_core_calculator.htm

Another technique is to wind sum turns on, measure the electrical/magnetic characteristics, then look up the properties in an old text like Bozorth and see what pops out.

http://www.micrometals.com/

I worked for this company some time ago as QC for production. We would measure the inductance of the cores after pressing and then do so again after baking. If the inductance didn't respond as we wanted it to, we would change the metal mixture, usually by changing the ratio of iron ferrite to iron oxide. Occasionally we could achieve our target range by just increasing the press pressure by several tons so more powder was included in the given dimensions.

ALWAYS we took multiple inductance readings before and after. Having sophisticated, high dollar test equipment was pretty much required, since we had to have accurate data. You can achieve something similar although not as accurate by using an inductance meter and freq. generator to plot inductance across a wide freq spectrum to differentiate between the different types of inductors. They are all designed for special uses and if you don't know what you have, you are just going to have to get lucky and try lots and lots of them in your designs. It would be better to just purchase what you need and be confident you have the proper material for your application.

Thank you for your replies, as with everything in electronics it is never as simple as you think it is. I would have imagined that they would have standardised colour codes like resistors. I would at least think that it would be easy to tell ferrite and iron cores apart by looking at them. I will have to devote some time later today to going over all the links in detail.

Building the "Inductor Test Bench" would be a good project and is definitely worth having a go at.

Seeing as this is not as easy as I first thought maybe I should explain what I am looking for any why.

I am looking for a good ferrite inductor in order to improve an old desulfator project, apparently you get far better performance using a ferrite inductor as less energy is lost within the inductor giving a stronger discharge. Another as a filter for a SMPS I intend to make soon, I have read they need an iron core because they offer better filtering properties. Another may be useful in order to make the SMPS transformer but I will most likely have to buy one specifically for that.



Here is a photo of them, it may be of use.


thanks

The tan toroid with part number 58930 is a Magnetics product; the material is called "High Flux", Al value is 157 (+/-8%, should be printed after part#), permeability (u) is 125.

Dimensions are:
OD 26.9mm, ID 14.7mm, H 11.2mm

To get a 220uH inductor, wind on 37 or 38 turns of up to AWG-18 magnet wire which will require at least 4 feet 4 inches of wire (add several inches for the ends). 37 turns should be ~215uH, 38 turns ~ 227uH.

To get a 1000uH (1mH) inductor, wind on 80 turns of up to AWG-24 magnet wire which will require 9 feet 1 inch of wire (add several inches for the ends).

The one to its' left marked CH270060 I think was a CSC product (Chinese), similar to a Magnetics 58894-A2
Al=75, perm=60, OD=26.9mm, id=14.7mm, H=11.2mm
To get 220uH, 54 turns of AWG-21 (max) requires 6 feet 2 inches minimum; should result in about 219uH.
1mH would require 115 turns of AWG-27, 13 feet 1 inch of wire (992uH). With this low of an Al, the impedance would be pretty high for use in a desulfator.

The large dark gray ferrite on the left will probably have a pretty high Al value. It was likely used for transient suppression.

The mint green toroid in the foreground to the left of the blue one has some numbers/letters on it. I think Arnold used that particular color. Arnold went through changes in its' product line a few years ago; I think they sold their toroid business to Micrometals, and the part numbering system changed. That makes looking up old part numbers problematic.

I had great difficulty finding much information on the 2 larger cores, all I found was similar ones, so that information has been of great help thank you. I only just noticed the writing on the little one.

As for the desulfator project, for this one I intend to use a slightly different setup to my past project. Some people have written about how they have had some fantastic results with lower inductance toroids with a far lower resistance value, which obviously boosts power . Lower inductance also favours lower AH batteries which mine are. I though I would have a go at using 120uH, 50uH or as described in one case 22uH inductor for L2. I will also be adjusting the timer settings to optimal level before saturation. As for the choke coil I will most likely just buy one as they are far more easily available in the specs I need. I do not even think it is critical that the choke is a toroid as its magnetic field should not fluctuate much. Correct me if I am wrong.

I will update you after I have done a bit more research. Thanks

Download the "Mini Ring Core Calculator" that I linked to above.
Use the "Unknown Cores" tab, and plug in the core AL that I've already listed, along with the core dimensions. Then you can plug in whatever uH value you'd like to see, and it'll tell you how many turns and what size wire you can wind on, and how much you'll need.

At the very bottom of that dialog there is a dark green window; if you type the # of turns in, it will give you a better idea of what the inductance will be. Of course, this is all depending on how accurate the toroid Al value is compared to what's listed in the manufacturer's specification. The variance can be somewhat significant.

On the Magnetics toroid, if there is for example a +2, -4 etc after the part number, you need to adjust the Al value by that percent. For example, if it has a -4 suffix, then you would multiply its' AL value of 157 by (1-0.04) =.96 to get Al=150.72, and then use that Al number in the Mini-Ring Core Calculator.

As far as the 1mH choke - that large ferrite to the left should work OK with around 20 turns of wire on it. Wrap that toroid with some masking tape before you wind the turns on, otherwise it might "sing" in your circuit.

Using lower values of inductance will cause the current through the inductor to increase much more quickly. You might find yourself going through some MOSFETs due to excessive drain current, unless you're really careful to stay well away from saturating the toroid.

Ronald Dekkers' page shows what happens to the current when the inductor becomes saturated. Once you enter saturation, all you get is more heat instead of higher output.

I have done a bit of experimenting with the toroids and their Al values. Most seem seem to be in the area of about 100-200Al however a few have shown to be higher. I have found 2 that are good for the 1000uH Inductors, the large green one with the bit of board lodged in its centre has an Al of about 6000 and the tiny green one not to far to its left has an AL of 3000 and reached 1000uH in 18 turns. The big ferrite one has an Al of about 2000.

I am wondering about how suitable it would be to use 2 separate inductors in parallel and how that would affect the function of the desulfator discharge pulse?

Would a MOSFET like this be good if I risk burning them as it has a very high current rating with very low resistance? http://uk.farnell.com/sanyo/atp301-tl-h/mosfet-p-ch-100v-28a-atpak/dp/1790737

In the past I have used single core wired that is used to make connections across PCBs rated for 1.7A on higher Al cores to lower inductance. It would also dampen the noise? Is this a good idea or must I use enamel wire?

Thanks

As well as needing assistance with the questions in the last reply I would appreciate it if someone could confirm or deny whether my basic concepts of how inductors work is correct.

How I think it works is that: As an inductor stores energy the cores available ability to store the current reduces and once it passes this point all current simply transfers to heat. I think this is how induction heaters work. High core Al value gives higher inductance for less turns but at the cost of the inductors ability to store energy. As a result inductance is more related to filtering and resisting change and has little direct relation to the inductors ability to store energy.

Also what is relevant to the topic: Iron cores tend to have an Al of a few 100Al and Ferrite has inductances of a few 1000Al?

It makes sense that this is also why high frequency transformers can be smaller and more efficient as they store energy and release it in small amounts rapidly rather than larger amounts less often.

Thank you

The black parts would be ferrite. See Magnetics Inc. or Ferroxcube for info. You should be able to locate the exact part by careful measurement of the dimensions of the core in comparison to the specs given on their websites; the material would be tougher, but the ideas given already should nail down the permeability closly enough. If the parts came from power supplies, that would be a clue, as not all ferrite materials are suitable for such use!

The painted cores would be powdered iron, maybe from Micrometals (http://www.micrometals.com/materials_index.html) which relies on color coding to identify the specific material. From there, it's just a matter of mechanical size! Be careful when measuring, as they round off the corners to prevent nicking the magnet wire, so you have to measure the maximum diameter, etc.

I am starting to get a good understanding of inductors. They are strange things. I am also beginning to get the hang of the core materials.

With a bit of luck and the information on these links I should be able to find out exactly what I have:
http://www.micrometals.com/material/pcprop.html
http://www.micrometals.com/material/quikref.html
http://www.bytemark.com/products/iptcpd.htm

I really wish I hadn't lost all my core Al measurements, I will start over again.

I must say the information can be a bit overwhelming and difficult to understand for someone who is not yet experienced at electronics.

I am hoping to get a better grasp of the physics behind inductors, I am still unsure if I have gotten the gist of how they work. It may be worth putting a topic up in the physics area asking if, how I think inductors work is remotely correct. What I have read has been challenging to understand and not answered all of my questions. Like all things electronic it will take time to figure out.