Types of Transformer and Choke Cores

[@itizme8072]

I'd almost bet you were, are, or should be an instructor, because of your knowledgeable, very thorough explanation, I enjoyed it a lot. Thanks for actually taking the time to teach others.

[@neilnagel9857]

Thank you. Very thorough and well explained.

[@ElectricMonkeyBrain]

thanks. glad you liked it

[@d614gakadoug9]

In general, silicon steel has used for transformers has the highest permeability of the materials shown, typically in the range of about 4000 to 4500. Ferrites *may* have permeability up to 10 000 or more but those used for power applications are typically under 3000. (Ferrite with initial perm. of 5000 is good for gate drive transformers.) Some have permeability of only a few hundred. Powder cores typically are made with quite low permeability - from tens to low hundreds. A core with permeability of more than 200 would be a rarity in power applications. The yellow core shown, assuming the hidden face is white (meaning Micrometals type 28 powdered iron) has an initial permeability of 75. Some ferrites have moderately high electrical conductivity. A shorting band around the outside is generally only used with flyback inductors which have a magnetic path with an air gap. In high-volume production usually just the centre leg is gapped. In low volume production a spacer may be used so all legs are gapped. The flux density in the air gap is very high and flux may be "slopped about." The shorting band helps reduce radiated magnetic flux. Pot cores are self shielding but they are very poor for power applications because they also keep in the heat from the winding. Ferrites are poor thermal conductors. The PQ core that looks a bit like a bow tie when viewed from the end is a type designed specifically for SMPS applications. It has a good set of compromises including quite large window area, round cerntre leg for winding efficiency and better shielding than simple E types. There are very low profile types suitable for transformers with windings made as multi-layer PCBs. Common mode chokes are very rarely used to keep noise out. They are to keep noise generated within a device such as a switching power supply from getting out onto the AC mains. Toroids are much better at self-shielding than E-I cores. They are, however, much more difficult and costly to wind. They are fairly popular for audio amplifier power supplies.

[@hamzakourta4509]

Very high value educational content, I wish you could drop some theoretical resources related to the topic in your videos

[@ElectricMonkeyBrain]

I linked some pdfs in another video, in the description. kzbin.info/www/bejne/l3mqln2DoLqaqtE Is this what you are looking for?

[@hamzakourta4509]

@@ElectricMonkeyBrain yes exactly, thank you

[@biswajit681]

Wow this is really great 👍👍 could you please make a series on transformer design??

[@ElectricMonkeyBrain]

well I can try. Its a good idea for a video. Any particular type of transformer you had in mind?

[@biswajit681]

@@ElectricMonkeyBrain may be can start with any low power flyback and Forward Converters transformer... I would be happy to become part of patreon

[@ElectricMonkeyBrain]

hi, thanks. Actually transformer design is quite complicated, it would take several videos. Perhaps I will start with a basic overview of the concepts.@@biswajit681

[@ElectricMonkeyBrain]

I managed to put a video together. Let me know what you think. kzbin.info/www/bejne/l3mqln2DoLqaqtE

[@instructoruldemeditatie2367]

Very interesting video and very well explained! But I have a question. I've been trying to understand how choke filters work for a long time. I know for example, and I also heard this in your video, that the higher the frequency, the greater the losses in the iron transformer. Doesn't that mean that the best filter for high frequencies would be iron? Why is ferrite used? Isn't this used in transformers such as flyback, or medium wave radio precisely because it doesn't block high frequencies? I don't understand this...

[@xenoxaos1]

The steel in the laminated EI core is a silicon steel. This reduces eddy current than carbon steel. There are even different grain alignments if you want to get expensive and specific.

[@ElectricMonkeyBrain]

Thats interesting, I didnt know that. Transformers have always been an interest of mine.

[@AkintobiOlugbenga]

Are there toroidal core that can work efficiently at 10GHz. I really need it😢