About Toroid inductors and magnetic field containment
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- Опубліковано 21 сер 2024
- #141 In this video I look at the particularities of inductors wound on toroidal shaped cores. I look at the specific propriety of such cores to be superior from a magnetic field containment point of view, and what are the specific details that need to be taken into account to achieve this.
References:
en.wikipedia.o...
w140.com/tekwi...
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Oooh yeah more magnetics videos!
One trick I've learn from amateur radio folks, when winding toroids for impedance matching autotransformers, is to wind the toroid until you get half way around the circle then loop the wire back to next to the start of the coil, and then continue winding around the other half of the circle (taking care to keep the winding direction the same), thereby creating two sections wound in opposite directions from the perspective of the circumferential coil so they cancel out - and also keeping the leads that form the ends of the inductor on opposite sides to reduce parallel capacitance created by them running parallel next to each other.
To be honest I remembered seeing this method and I did try it out but it didn't really work; now that I think about it, I mixed up the winding direction :))
My understanding is the purpose of such a winding technique is not related to Physics, rather to physically output at the opposite side. Specifically, SO-239 or BNC at one side, RF the opposite side of the enclosure. This technique works well for any ratio such as 49:1, 9:1, 4:1, and 1:1
73, KO4CES
Late to the party ... But I did want to thank FesZ for this video. It nicely answered a years old question of mine about toroidal leakage.
Just dropped by to say: solid series of videos, with the theoretical, the simulated, the implemented and the measured. Keep it up, all the best!
thankyou for sharing stuff like
and please don't stop doing
Thanks for taking the time to show us. I read about it wiki years back but forgot most.
Amazing quality content, as always ! Thank you for your work.
For inductors in switching power supplies the parasitic inductors are likely to charge parasitic capacitors in the commutation mosfet that will create an oscillating RLC circuit, rendering the power supply very inefficient and even unsafe. You can use an RC snubber to drain the parasitic inductor safely, preventing charging parasitic capacitors. The ( Spanish ) channel ACADENAS explains this really well, and today they will explain how to get values for the snubber. Maybe this channel could also make a short explanation for those who don't speak Spanish. Just a suggestion as unless one is a professional in electronics, most people are likely to use inductors for power supplies :)
40 years ago i had to wind a toroidal coil and it was a pain in the butt, Great video!
I wind them by hand 40hrs a week . I understand completely .
thank you
Thank you very much for creating all these awesome videos! I have already learned a lot from you and I think the way you explain and demonstrate your points is just perfect. Also, your selection of topics is great. Thanks again!
Hello again, I have just finished winding a mulit-layer step-up toriod pulse transformer. It was to have only two turns on the primary (for which I left about a 1-inch gap). The secondary was to have a couple hundred turns. I wound each layer to each end if the 1" gap, and was to place a layer of yellow mylar tape over each complete layer. For each layer, I used a separate piece of wire to avoid dealing with a very long wire for the entire secondary winding. To make it a continuous winding, I soldered the end of one winding to the start of the next.
I like to try using ODD numbers of layers so that the final secondary had it's ends on opposite sides if the primary gap. While winding the 4th layer, I discovered that I had wound it in the wrong direction! After thinking about it a while, I decided to 'jumper' one side of the 4th layer across the primary gap to the 4th layer to give the proper winding orientation of the 4th layer wrt the 3rd winding (BTW, I measure the inductance of the final two wires to make sure that it INCREASES with each winding). this seemed to correct the 4th layer WRT the first three. Now, I also got the expected increase in both inductance and spark length when the primary was pulsed. Also, this gave me a way to wind an EVEN number of layers and have the two end leads at opposite sides if the primary gap! In addition, I had several soldered taps, making many possible inductance selections.
Do you see anything undesirable here?
Thanks for all of your valuable information!!!
Great presentation!
Excellent video! Thanks!
In DC to AC power inverters, designers often include an inductor in series with the low voltage side of the transformer to limit the no load current. It would be great to if you could do a video on how to design/size this inductor for optimum performance. I believe the idea may be to select an inductor that has a high impedance at idle (limiting the current) but one that quickly saturates at higher loads and thus does not effect the transformer performance.
It is a Snubber or Line Reactor DV/DT. It would be an excellent project and some patents have already expired, making it easier to build...
@@ThinKkBIGG Thanks. I have found that on my cheep Chinese inverter the recommended 45 uh inductor cut the no load wattage by almost 1/2. The impedance of this coil is very low at 60 hz, but quite significant at the 22 kHz switching frequency where the iron core in the transformer would have a lot of losses. Don't know what a snubber or a line reactor is.
👍👍👍 ! Thank you !
Thank you very much, I finally understood a lot)).
Awesome explanations, thanks !
It would have been interesting to see what the inductance was for each case in addition to the leakage...
Me too. But also other things like saturation.
It is always a compromise between several things. Around 10 years ago I did a bunch of VNA measurements to common mode chokes for coaxial transmission lines. Very interesting to see what happend if you place several in series, or one big one, etc.
U must feature a video about ''chokes''!! Chokes, have became an integral structure in complex electronics!! best regards! super video! rubber heat shrink tube is used 4 shielding, from what I have observed!
I'm not sure that rubber has any magnetic proprieties, but I know that ferrite tubes are sometimes used - relatively long and thin, and a rubber heat shrink tube is placed over for protection - maybe this is what you are referring to. I will try to cover chokes at some point, what exactly would you be interested in regarding this subject?
Thank you for uploading this video.
I would like to hear your opinion on the effects of coils in three dimensions
That's interesting.
Thanks for this wealth of information! I'm using a 2-wire bifilar winding on my torroid and was wondering if the bifilar direction is enough to cancel these effects, or if I will need shielding?
I made lots of these
👍👍👍
Absolutely great video!
Could you maybe do a comparison between toroid inductors vs shielded ferrite inductors?
I am extremely curious what are the advantages and disadvantages of them for something like a DC-DC converter or Class-D power amplifier.
Do you mean compare emissions or electrical parameters in general (how they are vary for the same size component or something)
@@FesZElectronics I meant more in particular about toroid vs ferrite cores.
Having the same specs (in sense of current for example).
But yeah in general you could even add more to it :)
👍👍
When you run 7 wires in one direction and 7 in the opposite direction, why does this not cancel the magnetic field around the toriod, thus tending to eliminate the total lux in the core? (as seen at about timestamp 14:30 )
The wires are going in opposite direction only from the circumferential point of view; but from an axial point of view, all the turns run the same way (all of them are entering the toroid from the top and exiting on the bottom); so the only flux that will cancel out is the circumferential one - the "usefull" flux going inside of the core is not affected.
In my experiment, the field was not completely canceled because of the nonidentical distribution of the turns - being a hand wired coil it was not perfect.
It would be instructive to compare a pot core (say Ferroxcube) magnetic leakage to toridal core magnetic leakage !
Can you please make a complete lecture about making planar transformers? The one which is made from PCB boards? Thanks.
Good 😊😊😊
Nice demo & explanation! Should the return-turn be placed on the ID of the toroid, or the OD, or somewhere in between? Does this matter (and is it tunable)? If you strictly look at the top-view of the initial turns, they trace a "15-pointed-star" - the average cross-section of the star would be somewhere between the ID and the OD..
You also mention leakage capacitance being an issue for bifilar windings. How does this work for the leadwires? You have twisted enameled wires for the leads - wouldn't these have orders-of-magnitude larger capacitance than the overlapping windings themselves? Could (e.g.) a coax or a UTP leadwire help in this regard?
Do you think that a person needs to go to these lengs for toroids on a radio PCB that are fairly close to each other?
Some will be froon-end/IF transformers, some will be oscillator coils.
Great video, thanks for doing it!
73...
Nothing is really mandatory, but rather a measure for better performance; the closer circuits are, the more they will interfere with each other, you can either use measures to confine the fields from coils and circuits or just accept the limited performance. The more noise and cross interference there is in a receiver, the less sensitive it will be... Its like with an antenna - there's good ones and bad ones, but all of them will pick up the strong local signals - the difference will be noticed only with the very weak signals.
My output voltage is quite low on hand wound toroid transformer. I did match the frequency to source Ac, used proper core, and both wound in same direction. What is efficiency "percentage difference" of primary not wound exactly over secondary, just wound separate on core? It just looks visually better with 2 different colors insulation.,at separate placements on core.
You told us ways to reduce the field from escaping the core but you didn't really tell us why we don't want the field to escape.
Is it for more efficient coupling between the primary and secondary coils?
On one side it improves coupling - more efficient energy transfer from primary to secondary; on the other hand it reduces radiated magnetic fields - a problem if you need to pass compliance tests, or just want low noise in your system.
What’s the consequences to efficiency?
Just wondering why the toroid is not round but has 4 90 degree angles and if this would make an improvement?
I guess its easier to manufacture; also for the same general size you should have a larger core area; I don't think this will have an impact on performance since the main idea behind the "toroid" inductor is to get the magnetic flux to go in a circle; the exact shape of the coil should not matter all that much
@@FesZElectronics I would really love to know if a perfect toroid makes a difference. I will look to find one. 90 degree angles do make a difference.
what happened to solidity?
Have a question regarding 7:28, what is the purpose of this two ended inductor?
liked the experiment showcase the way you explained the return turns.
I don'r remeber where I got it from, but it was some sort of filter inductor I think, in a power supply.
@@FesZElectronics I have seen it in power supplies, but could not find the usage?
U
poorly presented information. why are you measuring in decibels? it would be more useful to show the current.
You obviously do not understand the purpose of this video or even first principles.