Skin and proximity effects: an intuitive explanation of Dowell’s loss model

[@robson6285]

The videolessons with the words "intuitive explaination" in the title are always the best, at least for me and i think for many of us. But when i read that it handles the skineffect i could not think how to understand that weird effect intuitifly. But indeed, that is indeed good to understand with this way of thinking about it. So after this explaination it has become one of my superusefull insights since i now have learned to not only understand but to see it, thanks to these videolessons. Ow when i could not use some things directly then still i love to follow and learn from these lessons because it gives us such a clear way to learn about the things most interesting for us. Thanks again, as always

[@sambenyaakov]

Thanks Rob for the insightful comment.

[@frankcharlesworth4580]

Excellent explanation of skin depth and proximity effects and how these problems are overcome in practice.

[@sambenyaakov]

Thanks Frank

[@himanshusemwal]

Thank you professor for sharing this knowledge. I recently encountered these hurdles due to proximity effect in my designs and I can really appreciate the effects of the measures you suggested in this video lecture. Your intuitive approach makes things easy to understand. Looking forward to learn many more such enlightening concepts from you.

[@sambenyaakov]

Thanks

[@32bits-of-a-bus59]

Thank you very much for a great video! The skin and proximity effects have always been a puzzle for me.

[@sambenyaakov]

👍🙏

[@narasimha4660]

Wow, professor your teaching way is amazing. Good information.

[@sambenyaakov]

🙏🙂

[@alirezatanehkar2009]

Very useful and beautiful presentation.

[@sambenyaakov]

🙏😊

[@mohammadhassanzade6893]

Great video Thank you Mr professor 🙏

[@sambenyaakov]

Thanks

[@weinihao3632]

Thank you for the nice explanation! Is it also possible that you show how to analyse the situation with FEA? Do you have a preferred tool which you can suggest for this analysis?

[@sambenyaakov]

Will try to add some more information. Have you seen: kzbin.info/www/bejne/b4O7XoJopNSfoqc

[@esijal]

Great Lecture 🙏

[@sambenyaakov]

Thanks

[@huanzhou4768]

Thank you for your video. For the Flat Wire Helical Enameled copper I can not understand why you take as One Layer. In fact I understand that they are several layers,,, Could you pls explain? Thank you

[@sambenyaakov]

If your cross section examination path is ferrite window, you see one layer of long standing wires.

[@grahamsopp]

Professor, could I ask about your interpretation of the Dowell at 24:20, multiplying layer 1 resistance by 4 and layer 2 by 12. Every other explanation of the graph takes the total resistance of the 2 layers and multiplies that by 12, which of course gives a higher value.

[@sambenyaakov]

You got me there. I was carried away. With two layers, the first layer is affected by the second one, so the Rac is smaller. Thanks for pointing this out. I will try to add a note on that in the description

[@grahamsopp]

@@sambenyaakov I've learnt so much from your videos, it's an honour to help

[@cpradeepk]

Hello Professor your videos are very informative. I always learn a lot.. can you upload video about the stability analysis of the peak current mode control, effect of sampling in the bode plot..

[@sambenyaakov]

Thanks. Will try.

[@ahmedkotb3912]

Hi, 25:14 , you took the curve for one layer for proximity effect. But in this case, there is only 1 layer so there should be no proximity effect losses. Shouldn't you have used the curve for skin effect losses only which you discussed earlier in the video? Thanks

[@sambenyaakov]

Thanks for comment. There is proximity effect in one layer (each wire from adjacent wire)

[@kraftrad7840]

What happens when I parallel a foil winding (connecting on the ends), that is half then one foil? Since Q will be less i move left on the chart. But on the other there are double layers. But overall, acording to dowells chart, the losses should be decreased. I did several experiments, its not working like this. Losses get worse, why? I assume since the parallel foils are not perfect parallel there is some area inside there parallel foils. Alternating flux will induce some voltage that causes current ind the parallel foil (shorted loop).

[@sambenyaakov]

Thanks for excellent question. I am holding on to my answer since I am contemplating a follow up video that will discuss this problem. Perhaps first as a riddle😊

[@michaelchang3234]

As you said, possible is internal current loop in the parallel winding. If so, how about break the loop? I suppose the two parallel winding is tied before the secondary recitifiers (maybe also two recitifiers). Then to break the loop, each winding could be connected to each diode, not tied to the other winding. These two paths would be meet at the cathodes. How about that?

[@kraftrad7840]

@@sambenyaakov Excellent! Im waiting. Greetings from Germany

[@kraftrad7840]

@@michaelchang3234 Can be done. But current will not be the same in each winding and rectifier. Its additional effort, especially when using synchronous rectification. Inductance (balance transformer) can be used to break the loop and prevent circulation current in the paralleled foil.But this also adds up complexity and cost.

[@michaelchang3234]

@@kraftrad7840 I'm not sure the reasons you consider parallel winding - high output current or further reduction of winding losses? In case of the former, multiple diodes or sync rectification are mandatory. So my suggestion is one of splitted winding by one rectifier (fet or diode). Diode forward voltage itself would be a kind of ballast for impedance imbalance. If the latter, too much paralleling (over an optimum point) would be not much helpful though Dowell curve tells less Rac/Rdc. Dowell curve is not linear, and it also seems it has an optimum point - Whenever I calculate and use Dowell curve, there is saturation point - which gives no more improvement.

[@FratilaRadu]

Why is proximity AC resistance not dependent of current level?

[@sambenyaakov]

Skin and proximity effects change the charge carriers profiles as a function of geometry and frequency. The current affects the intensity.

[@mehtabhussain4961]

Professor can you explain how can we apply dowell's curvea for helical configuration . As its geometry doesn't exactly allow us to apply dowell's curves and rather requires complicated analysis

[@sambenyaakov]

I really don't know of a good solution to that.

[@cihangiroksuz8172]

can you explain "How do ypu calculate "m" for "dowell formula"", please sir

[@tamaseduard5145]

👍🙏👍

[@sambenyaakov]

First again!😊👍🙏

[@k7iq]

😀😀