Toroidal inductors application cicuits - Page 1
Forum section: electronics / beginners

author: VSV_electron
author_rank: Regular Contributor
timestamp: April 03, 2024, 04:34:50 am
content: I bought myself couple dozen ferrite and Fe powder toroidal cores ranging from 9 mm up to 36 mm with different permeability values.Please refer me to some resources that would offer a variety of circuits to use toroids (either in single coil or coupled mode).So far I've only found how I can use smaller cores of 13 mm diameter in boost/buck converters.I wouldn't like to limit myself just to that.Where, for instance, I could apply larger 36 mm cores being used as perhaps some type of transformer?I've been always fascinated by the looks of inductors in the circuits and it would be sad to not go further than the limited power electronics area with these interesting components.I don't see many resources dedicated to this exciting subject except for some general info on those 1-page "All you need to know about toroidal inductors" would be tutorials that tell nothing.

author: MrAl
author_rank: Super Contributor
timestamp: April 03, 2024, 09:13:41 am
content: Quote from: VSV_electron on April 03, 2024, 04:34:50 amHello,Toroids are used in all kinds of power supplies, usually switching converters.One of the simpler ones is called a Royer Oscillator.Of course you can also make inductors, but the permeability of the core has to be right or else you have to be able to gap it yourself. There are toroids that have a distributed gap also, but you may or may not have any of those.It's not easy to gap a toroid though you would have to have some decent equipment. However, there is an unusual way to create a gap too. If you crack the core with a vise and glue the pieces back together, you get a multiple gap that is small but still works as a regular single gap. That allows you to get the effect of a gap without actually grinding a gap. It's interesting to experiment with this but you would probably want to have some cheap cores to start with.The iron type you can use to make a current transformer that gives you a step down in current and also isolation from the line. To do this you just wind some turns around the core, and the wire you want to use to measure the current in you put through the center which represents just one turn. The AC current gets stepped down by the number of turns of the secondary (with one wire through the center for the current measuring wire).If you want to get a little more exotic, you can create your own AC/DC current measuring transformer. You have to be able to cut your own slot through the toroid though or else get a toroid that is already slotted.You wind some turns around the core, and again the wire to be measured goes through the center. You place a hall effect device in the slot, then use a little feedback amplifier to measure the output of the hall effect device. The amplifier output powers the multiple turns winding.Now when the hall effect device measures zero, the output of the amplifier is putting out the same amount of current as the single wire, but lower by a factor equal to the number of turns of the multiturn winding. Because this is sensitive to both AC and DC, you can also measure DC current this way.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 03, 2024, 10:46:23 am
content: Well, if you have applications for 13mm cores, why not just do the same thing but 21.24 times higher power, for the 36mm cores?Perhaps what's missing is an understanding of scaling laws. Anything you can do at 1W, works at 100W, or 1,000,000W. Well, there are good reasons not to do exactly the same thing across those scales, but the basics, the power flow architecture, is more or less there, and the majority of differences lie in the control schemes (as that 1MW unit will be much more expensive, and it's wise to add some more subtle control and protection features, safety interlocks, etc. to protect that investment, and those working around it).The actual ratio will be a bit lower, because temperature limits tend to go as 3/2 power, but there are ways to scale faster as well, like running in deeper CCM to reduce core losses. Or maybe the 13mm model didn't get particularly hot, or a fan is acceptable on the 36mm model.Tim