Which Color Toroid and Ferrite material is best?

MrAl said:

Hello there,

If there is any DC current in the winding that could easily lower the inductance that you see when you only have an AC current. This means it saturates easier and steps have to be taken to minimize that.

So the obvious question is, does the application you intend to use this for have any DC current?

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DC current affects the saturation rating of the core. It's magnetizing effect uses up some of the core capacity and hence it saturates more quickly.

Mosaic said:

DC current affects the saturation rating of the core. It's magnetizing effect uses up some of the core capacity and hence it saturates more quickly.

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I didn't know that. TYVM.

gary350 said:

Learing Experement.

I used 42 enamel coated #30 copper wires. I twisted them a little just so they would be easy to put through the 9 toroids I have taped together. I have 12 turns of wire. Cross sectional area of 42 wires is = to 14 gauge copper wire rated for 15 amps. This is a learning experement to see if larger wire can handle more current and not get hot and also to learn the mh value of the coil.

A 2 minute run at full power and the large choke was still room temperature. This is exactly what I wanted to know. Maybe #14 solid wire would get warm because it is less surface area and less cooling than 42 seperate wires.

2 toroids with 11 turns of wire = 1 uh so 9 toroids with 11 turns of wire should be 4.5 mh. I have 12 turns of wire = 6.3 mh. I know 1 extra turn did not increase it by almost 2 mh. Does the increase of almost 2mh have something to do with using higher current wire or using 42 wires?

Almost forgot to mention wire resistance of the 42 wire 6.3 mh choke = .3 ohms. Wire resistance of the 8 mh choke = .4 ohms.

Look at the toroid mounted to the induction heater circuit with 38 turns of #18 enamel coated copper wire wound on 1 toroid same material. It is 8 mh and gets too hot to touch after 2 minutes. If I dont turn this off at 2 minutes the choke starts to smoke.

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Great idea.

gary350 said:

I need a 26mh choke rated for 60KHz.

Defination of permeability is a material that passes water. Low permeability will be a dense material. High permeability will be a softer material.

Deffination of low permeability. Used widely in power transformers, current transducers, instrument transformers, inductors, chokes, ballasts, voltage stabilizers and regulators, welding transformers, broad band transformers, filters, etc.

I have no clue what I am looking for?

$10 each for a 1.9" diameter toroid seems expensive.

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Is this for the induction heater?
Why do you need a 26mH choke?
Such a big choke either wastes power or it is saturating with high currents and then it is useless.
In the original circuit one 2mH choke was used and it worked?

Here is another simple induction heater:
https://4hv.org/e107_plugins/forum/forum_viewtopic.php?122354
It uses two chokes < 470uH and the working coil is without center tab.

Honduras said:

As I understand it, DC passes through an inductor with no impedance except for the resistance from the wire.

DC is not involved in the formula for inductive reactance. Only AC frequency and inductance.

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Hi again,

You dont know how much i wish that was true. But unfortunately DC current affects the inductance so the AC behavior changes too when there is a DC current in the inductor. This is especially important for switching regulators because they always have DC current. If the DC current brings the inductor too high up on its magnetic curve, the permeability goes very low and that kills the inductance. Thus if we start out with 100uH inductor when zero DC current, we might end up with an inductor of only 1uH if significant DC current flows.
This of course affects the reactance, lowering it significantly.

Most of the circuit theory for things like reactance assume a LINEAR magnetic curve for the core material, but the only core material that is linear is no core (air). All the rest are considered to be anisotropic (see diagram) or hysteretic.
In the diagram shown, the horizontal axis is the excitation which is usually denoted by "H" and is proportional to the ampere turns (N*Idc). The vertical axis is "B" or flux density. As the DC current increases, B increases sharply, but then as the DC current increases more, there is less and less change in B which means the permeability became must lower. At "u1" the permeability is fairly high, while at "u2" it is lower, and at "u3" is is very much lower than it was at "u1". Since the inductance is proportional to permeability that means the inductance fell quite a bit between "u1" and "u3".

This is why we have to know if your circuit has any DC current. Winding turns around a core means we get some inductance, but that inductance is easily reduced by the DC current in the circuit especially if the core material has a high initial permeability. The only way around this is to add a gap, and that isnt easy because even a small gap affects the inductance by a great amount, so gaps are typically very small, even thinner than that which you can make with the thinnest Dremel diamond cutter wheel.

I am learning more about chokes than I did in college. A choke is an AC device. A choke will pass DC with no problem. If you modulate DC with AC then you have problems. I know a choke in a tube amplifier circuit is always used for current limiting. I used a choke on my Tesla Coil for current limiting too, I could adjust the power from 10kw to 14kw and there was no change in the output arcs above 12kw so to avoid wasting power I ran the TC at 12kw. I assume a choke in this inductance heater circuit is for limiting current too, blocking RF an still allow DC current to the Mosfets?

I seem to have the 15 vdc power supply problem solved with higher 200 volt capacitors and .1uf, .01uf, .001uf filter caps in parallel with the electrolitic caps so maybe the choke is not very important for keeping RF out of the power supply.

I need a good amp meter. The 20a fast blow fuse I need for my meter will take a month to arrive from China, no one sells anything larger that 10a in the 5mmx20mm size. Maybe I can solder a 6mmx30mm fast blow fuse in parallel with my bad fuse and get my amp meter working again.

I need to test several different chokes to see what that does to current, voltage and frequency on both sides of the chokes then compare that to the output of the LC coil.

Sounds like you have a resonant oscillator which is being powered through the choke, the idea is that the osc can be powered from dc, but the ac generated by the osc is not shorted out by the power supply as the choke prevents it.

A choke will saturate at a certain current, or volt seconds, the dc current flowing to the osc in conjunction with the ac waveform both contribute, the choke material or more aptly the surface area through the torroid must be big enough to take the resultant flux density.

N87 or N97 are good materials for power chokes up to around 150khz, using nondescript torroids isnt a good idea.

Dont put another fuse in your meter, you will not be protected by it as intended.

NEW DISCOVERY

I read online that is makes a difference how the capacitors are connected. I had to try this to see for myself.

Top Photo. 8 capacitors in a straight line 2 banks of 4. This takes 55 seconds to heat a 3/8" steel rod to 1300 deg. Frequency 86 KHz with no load, 64 KHz loaded.

Second Photo. I changed it to 2 banks of 4 with discharge at the center. This takes 60 seconds to heat up a 3/8" steel rod to 1300 deg. Frequency 87 KHz with no load, 73 KHz loaded.

I learned something else. My capacitors have 2 Dot markings on 1 side. Before I had them all random mixed up with double dots on both sides. Does anyone know what those 2 dots are for?

I have reconnected the capacitors in a straight line again but this time all the 2 dots are on the same side. As before 3/8" steel rod is 1300 deg in 55 seconds.

I know form making my own Tesla Coil capacitors .01 uf 40KV a flat plate capacitor is physically 2 times larger than the same .01 uf ROLLED capacitor and produces more power output.



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Don't know about the 'dots' but do know those caps are rolled inside the plastic case. The leads are then metalized 'spray welded' to the internal sheets of the cap.

The Dots probably represent the Outer foil (Plate) of the cap.
Not really a Polarity, but somewhat related.
I have seen simular markings like this before, and it can be important for some applications.

Greetings !

I am doing research on various mixes of ferrite sleeves and toroids and I was wondering what the significance the color of the coating is with regards to the 'MIX' type and composition ? I would sincerely appreciate any info that you may be able to impart ! Thanks in advance for any and all assistance ! 73 de Mark, Amateur Radio Station WN3SIX

gary350 said:

I bought some Green 10mm x 25mm Ferrite Toroids from China.

1 Green toroid with 11 turns of wire on makes a .5 mh choke.

2 Green toroids taped together with 11 turns of wire makes a 1 mh choke.

4 Green toroides taped together with 11 turns of wire makes 1.8 mh choke.

1 TV toroid white snap together plastic case with 37 turns of wire same physically size as 1 Green toroids makes a 8 mh choke.

2 black natural color toroids taped together 4 times larger than 1 Green toroids with 11 turns of wire mades a .2 mh. Larger is NOT better.

I am looking for toroids in several places and not finding much. I bought toroids from Jameco in the past but they no longer have toroids listed. Ebay has some but there is NO date about the toroids. I checked several of the parts companies listed on this forum not finding many toroids. One place called West Florida Components has a small .8 inch toroid that says it his high flux. I'm not finding pre made chokes either.

Will higher flux make a higher mh choke?

Any suggestions where and what to buy I want to make a 26 mh choke?

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Mark G. Cooper Sr. said:

Greetings !

I am doing research on various mixes of ferrite sleeves and toroids and I was wondering what the significance the color of the coating is with regards to the 'MIX' type and composition ? I would sincerely appreciate any info that you may be able to impart ! Thanks in advance for any and all assistance ! 73 de Mark, Amateur Radio Station WN3SIX

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Micrometals.com set the default mix color codes for iron powder cores over the past 50 years. Other companies have followed essentially the same rules. There are many types of iron powders based on size, carbon content, microsrructure and more. The carbon-free (hydrogen reduced/soft magnetic) iron can handle higher saturation current but lower saturation frequency. Datasheets are available on websites of the core manufacturers websites.

If you need even higher frequency than iron (hard or "un-annealled") can handle, you can look at Sendust (iron/nickel alloy) or "mu Metal" from Magnetics Inc. For even higher frequencies, use Ferrites. Ferrites are ceramics that have magnetic effects - they are not made of metallic (elemental) alloys, they are made from partially oxidized iron, cobalt, nickel oxides, silicides and more. As always, materials that can handle higher frequencies have lower saturation current.

The color codes for iron/nickel alloys and Ferrites are not as well defined for each "mix" as the iron powder mixes used by Micrometals so tracking down a datasheet from the specific manufacturer is best.

If you only have a few to test of each core, you are best off winding your own bare cores.

Greetings To All !

I have recently decided to do a little research and attempt to find out what the proper method was to identify 'mystery' ferrite toroids and snap-on ferrite cable 'beads' or 'sleeves'. I have a box of a small assortment that I managed to salvage from some cables that I discovered in the trash bin of a local company. Since the 'snap-on' split core ferrite 'sleeves' are quite pricey from most vendors and the fact that I had 60 or so snap-on split core sleeves in my stash with an inner diameter of .505 inch, I thought it would be prudent to finally try to determine their 'MIX' type in order to determine their usefulness around my amateur radio (Ham) shack. I was particularly interested in determining the 'mix' for these in particular since their inner diameter is .505 inch size which fits perfectly on RG-8/U, RG-9913 and LMR400 coaxial cables, the exact type of feedline cables that I use for my ham radio gear.
Upon doing a bit of research I was intrigued by what I discovered, and just how simple of a process it is if you are fortunate enough to have the luxury of owning or borrowing an 'Antenna Analyzer' such as the MFJ Model 269C or 259C, or similar antenna analyzer, http://www.dxengineering.com/parts/...zRUSbfOgCwPrMiHiInnRockFqAHc1fn8aAozsEALw_wcB
Fortunately for me it was easy to get access to using one of the MFJ analyzers since two very nearby fellow ham radio friends has one each, one a MFJ unit, the other, I can't recall the make or model presently, but a good quality commercial analyzer nonetheless. I was thrilled to discover that I had ready access to one of these two gems since they are a bit pricey for my casual use.
For the sake of about a half-hour of work, I cobbled together the required 'test jig' using a 50 ohm coaxial cable jumper about a foot long with PL-259 connectors at each end and a single type SO-239 RF connector, an alligator clip and a 6 inch piece of copper hookup wire, it doesn't get much easier, or cheaper, than that !

For the benefit of those seeking to ascertain the same, I came across this simple 'test fixture' and explanation of how to use it to determine, once and for all, what 'MIX Type' those mystery ferrites are, whether you have scavenged them from old cables like me, or have seen them at electronic flea markets or 'hamfests' or on EBay ! In fact, if you are lucky enough to own an antenna analyzer of your own, it is just portable enough to carry along at hamfests for electronic flea markets and determine the MIX type before buying, to ensure you are, in fact, getting what you are paying for ! Once you become accustomed to the test procedure, you can easily determine the mix type in less than a minute or two ! The process is quite simple, as you shall read from the information I gleaned online and have thoroughly tested, for accuracy. See the procedure and information below:

TEST SETUP (Test Jig)

All that is required in order to evaluate ferrite cores, beads, sleeves or snap-on's, is a short length of RG-58/U or other 50 Ohm impedance coaxial cable, about a foot or so long, length is not critical, with PL-259 RF connectors at each end, a Type SO-239 RF connector and of course, your antenna analyzer of choice similar to the MFJ Model 259C or 269C.

The 'test jig' consists of the following: Solder a short length of copper hookup wire, around 22 or 20 gauge or similar, again, not critical, to the center connection of the SO-239 connector. Strip off the insulation at the free end of this wire. Connect a short length of the same type of hookup wire to the ground side of the SO-239 RF connector. You may either solder the wire to the ground side of the connector or fasten it using a machine screw and nut. Solder a small alligator clip to either of the two 'loose' ends of the hookup wire affixed to the SO-239 connector. This method makes for a quick and easy method for quickly swapping out ferrite toroids or sleeves to be measured.


TEST PROCEDURE

Simply connect your antenna analyzer, using the short length of coaxial cable, to the SO-239 connector. Insert your ferrite product to be measured into the 'open' loop and simply attach the alligator clip to the other loose wire on the SO-239 connector and you are ready to roll !


You've seen a big box of cheap ferrites at the surplus place. What kind of ferrite are they? What's their properties? This question comes up all the time, so here's some info on identification.

First, the statistical approach... Most all of the shielding ferrites you see are Fair-Rite Type 43, or the equivalent. The permeability is around 1000 for lowish RF frequencies (<1MHz), and they become mostly resistive.

Measuring using an Antenna Analyzer (as long as it reads both R and X)

(Suggested by Scott Townley) Loop a single wire through the core. Run the frequency up until R=X. The mix is identified by the following:

Mix 33 - around 10 MHz
Mix 43 - around 20-25 MHz
Mix 61 - around 50-70 MHz

(Additional mix values listed below)

The FairRite Catalog (http://www.fair-rite.com/) has actual tables showing impedance vs frequency for a one turn loop. You'll have to measure your particular ferrite and find one with matching specifications.

Chuck Counselman cautions that measuring the inductance at too high a frequency can perturb your measurements, because all these materials start to become quite lossy at higher frequencies, the frequency at which this occurs being dependent on the material (which is how Townley's scheme works, really).

A bit of reading of the Fair-Rite catalog will greatly repay you. The URL (as of 13 May 2018) is http://www.fair-rite.com/files1/Fair-Rite_Catalog_17th_Edition.pdf

Amidon Associates also has data **broken link removed**but it's a bit harder to find.

Additionally, you will also find a wealth of useful, very informative information on the Palomar Engineers website at: http://palomar-engineers.com




Identifying ferrite materials



Note that ferrite materials are subject to manufacturing tolerances and variation with temperature, so do not expect 1% accuracy in applying datasheets to real cores.

Table 1: Selected Fair-rite data
Mix Frequency where R=X (MHz) µi
31 3.6 1500
33 4.5 600
43 14 800
52 30 250
61 43 125
73 2.3 2500
77 1.7 2000
Table 1 shows the cross over frequency and µi for some common Fair-rite materials. It can be seen that although #33 and #43 have similar µi, their RF performance is quite different, due in part to the fact that #33 is MnZn ferrite and #43 is NiZn ferrite. If one was to classify an unknown core of type #43 or #33 based on µi alone, allowing for manufacturing tolerances, temperature and measurement error, it would be very easy to wrongly classify it.

Likewise, other manufacturers may have cores of fairly similar materials, and measuring µi alone gives no indication of the RF performance, or a valid comparison with a known core.

***NOTE --- If I have regurgitated information already presented here in the past, I apologize, my goal was to outline the procedure for those who may be exploring these fascinating ferrite products for the first time, hopefully providing a shortcut, to my hors of research on the subject.


If you would like to comment or make suggestions you may reach me at: highmountainradio@gmail.com

73, Mark, Amateur Radio Station, WN3SIX

Many thanks for the excellent and very informative information ! Right now, my primary interest is working with ferrite products, however, I have saved your terrific explanation for future reference !
Best regards, Mark..

gophert said:

Micrometals.com set the default mix color codes for iron powder cores over the past 50 years. Other companies have followed essentially the same rules. There are many types of iron powders based on size, carbon content, microsrructure and more. The carbon-free (hydrogen reduced/soft magnetic) iron can handle higher saturation current but lower saturation frequency. Datasheets are available on websites of the core manufacturers websites.

If you need even higher frequency than iron (hard or "un-annealled") can handle, you can look at Sendust (iron/nickel alloy) or "mu Metal" from Magnetics Inc. For even higher frequencies, use Ferrites. Ferrites are ceramics that have magnetic effects - they are not made of metallic (elemental) alloys, they are made from partially oxidized iron, cobalt, nickel oxides, silicides and more. As always, materials that can handle higher frequencies have lower saturation current.

The color codes for iron/nickel alloys and Ferrites are not as well defined for each "mix" as the iron powder mixes used by Micrometals so tracking down a datasheet from the specific manufacturer is best.

If you only have a few to test of each core, you are best off winding your own bare cores.

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I have learned to buy 20 bargain toroids then wind 20 turns of #14 copper wire on 1 toroid then test it to see what the value is. If it turns out to be 1uh and I need 8uh then I put 8 toroids in a stack and wind 20 turns of #14 wire on it then test it. It is usually very close to the value I need adding 1 or 1.5 more turns will get me 8uh that I need. #14 wire is rated 15 amps I can pull 50 amps, 21 volts, 100KHz, on this 8uh choke for several minutes and it never gets hot. If you test several different colors you can put your own ratings on them.

The most complete info I got, came from a leaflet I received via snail mail, IIRC, from Amidon. Color, codes and all data you could need for their different products. At the moment it was more than enough to use them.

That was about four years ago.

gary350 said:

I have learned to buy 20 bargain toroids then wind 20 turns of #14 copper wire on 1 toroid then test it to see what the value is. If it turns out to be 1uh and I need 8uh then I put 8 toroids in a stack and wind 20 turns of #14 wire on it then test it. It is usually very close to the value I need adding 1 or 1.5 more turns will get me 8uh that I need. #14 wire is rated 15 amps I can pull 50 amps, 21 volts, 100KHz, on this 8uh choke for several minutes and it never gets hot. If you test several different colors you can put your own ratings on them.

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You have to test at the max expected current or you may be surprised by the inductance falling off for some core materials.

i have a MFJ analyzer, thank you for the information about identifying toroid materials!

wow, this thread has been exhumed, original thread was 2015

Personally, I would never trust a toroid colour code unless I knew who made it, and had a copy of their colour code in front of me. There are all kinds of strange mix toroids in switchmode power supplies and common mode chokes with all kinds of different colours that don't remotely relate to the Micrometals colour code.

As previously discussed, doing a test winding is a good idea. From that you can get the AL value and from the AL and the toroid dimensions you can get the permeability which will give a good idea of what frequencies it's good for. General rule of thumb: The higher the permeability, the lower the frequency. Most of my toroid inductors are for medium wave radio circuits which max out below 2 MHz, and I use type 61 mix which has a permeability of 125. So, that may give a rough idea of what permeability values are needed for higher or lower frequencies. Manufacturers show recommended frequency range and permeability for different ferrite mixes in their data sheets.