Looking for Ferrite cores overview

Do you need to wind an inductor? There are a lot of stock parts out there.

I never found enough difference to be worth worrying about. What was frequently difficult was finding somebody who stocked a range of parts in depth and would ship in small volumes.

was useful - more than ten years ago - and still seem to be in business.

John Larkin's point - that you can buy quite a few pre-wound inductors - is less relevant if you are thinking about transformers, which have more windings, so that off-the-shelf transformers are rarely even feasible and even thn mostly wildly sub-optimal.

This is for a halfbridge converter, pushing size and performance, so it's not possible to use stock parts. In addition stock parts are

++expensive ;-)

It's a transformer, and true, stock parts will most often be suboptimal (except for zero leadtimes)

I was successful buying from this US house,

. They had MPP toroids from a Korean manufacturer, no worse if not better than these from which I could buy from a German house initially, shopping was easier, prices were better etc. (about 10 years ago the German operation would not accept payment via credit card, other than that they were OK, too - but costlier).

Dimiter

Winding is more expensive!

I used some stock toroids on my h-bridge amp. With lots of air!

MPP is expensive. Kool-Mu and sendust can be as good for power applications.

Micrometals has a New! Improved! cost-optimized power material:

Nice, they have a lot of different cores. Thanks

It depends on the quantity, and where you buy. Chinese do very small runs. EU/US you need 50k+

Nice looking parts

That's odd. In my time - ten years ago and more - there were always local coil winders. They weren't as cheap as people who were geared up for high-volume work.

The last one I used

is at Horst in the Netherlands, which was the closest one I could find to Nijmegen. Nijmegen does have a specialist transformer manaufacturer, but they make much bigger transformers than I was interested in. Our cleaning lady's husband worked there ...

That sort of choke is available from broad-line distributors like element-14. Common mode chokes - that look much the same - even have a second winding.

For comparison, I assume you're meaning material properties.

For power applications, core loss is probably the most picked-on feature, despite the poor tolerance and temperature dependence.

There are two tables in my files, from work in the 90s, up to about 2004. These are spot frequency losses at either

85C or 100C, pulled from published charts for the specific material, supplied by their mfrs.

This is the sort of thing that can be added to, or altered,as you examine possible vendor offerings, for later comparison.

Comparing Steinmetz components is probably a waste of your time.

If your application depends critically on core loss, you're picking the wrong horse to ride on.

RL

Actually, looking closer, I see these charts were actually from a

2004 thesis by Fu Keung Wong,"High Frequency Transformer for Switching Mode Power Supply", with the lower frequency table being attributed to Abraham Pressman in 1991.

If you google for "core losses for various ferrite materials", you'll get at least one good link for the original thesis, not just the index.

Knew there was something wrong after noticing the chart headings.

Also W/m^3 is probably a typo. Core loss generally expressed as KW/m^3 or mW/cm^3 (~=).

RL

Sendust is said to be *almost* as good and it is cheaper, don't remember what Kool-Mu was (IIRC it was about the same as sendust). Nothing is as good as MPP and the cost of a few toroids is not a huge factor in the netMCA where we mainly use them (

, board photo with the MPP toroids at the page bottom, takes scrolling).

Initially I tried iron cores of the same size from Micrometals but they were getting too hot in the flyback (the central one,

+/-15, +/-24 and -5 volts), IIRC I talked about it here and you mentioned an occasion on which you burned their paint off... I did not go that far, in fact it was still usable but the board would have needed active cooling and the MPP core solved this completely. The 4 stepdowns at the left are not dramatically better with MPP than they were with iron cores but we just stock and use that MPP size, runs a little cooler as a bonus.

Dimiter

Yes, I worded it wrong. For 50k+ they would be at almost the same cost as real high runners. In the EU/US the scale is much higher before the cost flattens out

Yes, coreloss is difficult. Different ways to measure, different ways to present the data etc

I am looking at u/AL value vs temperature for example in the same size series. So that I could select second sources that could be interchanged to actually work

In ferrite power applications, you don't generally store any energy in the ferrite, so permeability isn't of major concern. The effective permeability and energy storage of the structure is controlled by the air gap.

In single-order filters, F1 is highly dependent on permeability, but F2 is again mostly a structural issue. From memory, it has a positive tempco below the curie temperature, but you can kill it with mechanical stress in assembly. Again - a gap gives a closer, more controllable tolerance.

RL

Yes, I have burned the paint off Micrometals iron powder cores. KoolMu fixed that problem.

This was a 120 amp 3-phase buck switcher.

Are those drum cores actually ferrite?

RL