solved: figuring out magnetic core materials (sendust/iron) in 2 catalog items? - Page 1
Forum section: electronics / projects

author: incf
author_rank: Frequent Contributor
timestamp: April 07, 2025, 09:35:54 pm
content: I'm new to inductor power loss calculations.I tried asking the manufacturer, and got no response.There are two toroidal inductors that I am interested in estimating/modeling losses for.Bourns 2205-H-RC - which uses a high loss iron powder core of unknown permeability18 turnsInductance factor of 67nH (I think? 22000nH/18^2)core might be similar to (except the core is twice as tall and iron powder not XFlux):https://www.mag-inc.com/Media/Magnetics/Datasheets/0078206A7.pdfBourns 2300LL-220-H-RC - which uses a low loss sendust core of unknown permeability11 turnsInductance factor of 181nH (I think? 22000nH/11^2)core might be similar to:https://www.mag-inc.com/Media/Magnetics/Datasheets/0077930A7HT14.pdfI have physical access to samples, but lack the test equipment to directly measure temperature rise vs frequency and magnetization. I could unwind the inductors to try to measure the core dimensions if needed.I'm hoping to figure out what the permeability of the cores probably are, and then to track down a datasheet with core losses for said material.I found a datasheet for Sendust losses fairly quickly, but I've had a harder time finding a catalog of iron powder core materials and losses.Is "iron-powder" the same as "XFlux" iron-silicon?Edit: I guess iron powder is different from XFlux, but still having trouble getting any sort of data.  suggests that maybe iron power has 10x the losses of Kool-Mu/Sendust under identical operating conditionshttps://www.mag-inc.com/Products/Powder-Cores/Learn-More-about-Powder-Cores/Powdered-Iron-ComparisonEdit2: I'm beginning to think that "iron powder" could mean literally anything with regards to material characteristics. I found one or two old graphs, but I can't be sure of their applicability.

author: jonpaul
author_rank: Super Contributor
timestamp: April 07, 2025, 11:33:57 pm
content: Powdered Iron: Many mixes availableBest vendor is Micrometals.comExtensive catalogs, calculators, specs on losses and shapes.We know the founder Jim Cox since 1970s, a great engineer and longtime Hamhttps://www.micrometals.com/Other vendors and catalogs:TDK (MH&W Internationals)EPCOS (Siemens/Philips)Magnetic MetalsMagnetics IncSendust is high cost high perm like Supermalloy and amorphous.For special purpose only very costlyJust my experience since 1970s.Jon

author: incf
author_rank: Frequent Contributor
timestamp: April 08, 2025, 12:08:12 am
content: Quote from: jonpaul on April 07, 2025, 11:33:57 pmThe micrometals catalog and design tools appear to be exactly what I need.

author: Wolfram
author_rank: Frequent Contributor
timestamp: April 08, 2025, 07:39:47 am
content: Powder cores are a large topic, with tons of recent developments.It's hard to draw any conclusions from the permeability, as most materials are available in a range of permeabilities. For the older materials, this used to be specific to the material type, but more modern materials are commonly available in permeabilities 26, 40 and 60, with some materials also available in 19, 90 and 120.Traditionally, they were made from pure iron powder and organic binders. Hydrogen reduced iron for low frequency cores like Micrometals 26, 52 and others, and carbonyl iron for high frequency cores like Micrometals 2. The hydrogen reduced iron powder cores are more or less obsolete these days for power conversion, as they have pretty high loss and thermal aging from degradation of the binder.For the last few decades, most of the development has been in ceramic bonded alloy powder cores. Everybody has their own trade names for these materials, so it can be a bit confusing, but they generally use the same few alloys.FeSiAl cores (Sendust, KoolMu) are low loss and low cost, with moderate saturation flux density.Ferrosilicon powder cores (Mega Flux and others) traditionally had much better saturation behavior, but higher loss, still at a low cost. Recent developments have made these core materials much lower loss, so the cost-loss-saturation tradeoff is very good with these materials. I've used a material with 69 % permeability retention at 100 Oe, and 112 mW/cc loss at 1kG/50kHz, with a cost comparable to Sendust. So these materials have advanced a lot.Permalloy cores were the traditional performance option, using a large fraction of Nickel in the alloy. High-Flux is an example of such a core material. Saturation and loss behavior are very good, but cost is high due to the Nickel, especially given how Nickel prices have developed over the last half decade. There have also been a lot of development of these materials, mainly in the processing of the powder, which has reduces losses drastically. So an older generation Permalloy material will not be very competitive when compared to a more modern Ferrosilicon material, but the latest generation Permalloy materials have excellent performance, at a cost.Historically, there were other materials like Molypermalloy, but these are more or less obsolete for commercial applications now since cheaper materials have overtaken them in performance.And then you get materials which are blends of these alloys, and also amorphous distributed gap cores, all using manufacturer trade-marked names. In the end what matters is bias behavior, loss, and cost, so this is what I recommend comparing. When buying ready-made inductors, the manufacturers rarely give any info on core material and loss, if you're lucky there might be some info on inductance vs. DC current. For this reason I always found it better to to have the inductors custom made for applications where performance and cost matters. Regular component distributors usually have a very limited selection of magnetic materials, with very high pricing, so I recommend looking for a distributor specialized in magnetics if you want to go in this direction. In Europe, Semic and Feryster come to mind.