A deeper look at the approximate design of power inductors with gapped ferrite cores

[@ANoNIMkillir]

Professor, thank you for providing such wonderful educational videos in English. This is a unique opportunity to learn for everyone. This is very generous of you!

[@sambenyaakov]

Thanks Vasiliy.

[@arushsinha6839]

Sir, thank you so much for posting this video. It really helped me in my power electronics thesis. I was stuck on this problem for a while and was reading a book which was very complex and not intuitive and was stuck on it for a long time. Through your video I was able to move my thesis along and was able to write a good explanation, which helped give me a good mark. Please keep up the amazing content.

[@sambenyaakov]

Thanks for taking the time to write this note. Comments like yours keep me going

[@tangy1181]

Just one video after one video and another video from yours.... cannot stop. good job!

[@sambenyaakov]

Wow, thanks!😊

[@guidodiiorio6183]

Thank you so much professor! I work in power electronic design field and I always found very unclear how to choose a core properly... Your video clarified a lot of my doubts I have always had))) thank you so much!

[@sambenyaakov]

Thanks for kind note.

[@harin188]

Hi Sam, It's nice to have Ur KZbin channel with crystal clear concept in short videos... I like to know about the frequency selection for a particular design requirements... Hope you can share your thoughts on frequency selection for a particular set of design requirements....

[@sambenyaakov]

Thanks. That is a good subject. Will try

[@foobarables]

Fantastic video. But I have a few question or perhaps a riddle for you. @ 5:55, Bpk is selected to be maximum 300mT. But is this correct? Because the plots were generated with a core heated by external means too 100°C. In a real application the core will heat up because of core losses and the core "core" temperature might be much higher than the core surface temperature. 3C95 material has a thermal conductivity in the range of 4.01 W/m.K, which is in my minds eye given the core thickness is not that high.

[@sambenyaakov]

I would say that 4 W/mK is not that bad considering that the surface is much larger than the thickness.

[@the-incomplete-engineer]

Hi Professor, I tried to do the air gap calculation using the same approach in my design. I have an inductance of 3mH, N - 84 and Ae - 3.79e-3 m2. This gives an air gap of 11.2mm. This seems a bit too much for inducting a lot of air gap reluctance in the path. Could you help me verify this?

[@PrashantSharma-ve3bd]

Hello Sam, You are always my favourite due to your very crystal clear concepts and fundamentals of your each represented video yet, I expect these topics from you : - (1) inductive coupling in input power filter (ex. Pi filter) (2) wireless power transfer : Present solutions & topologies (3) Ground : Myth & reality in SMPS design (4)RCC (Ringing choke converter ) with coreless transformer (5) Loop Compensation in SMPS design : Myth & Reality

[@sambenyaakov]

HI Prashant, you have quite a long wish list. At least 50% of the subjects are already covered in my KZbin channel. Look them up.

Professor, thanks for the videos they are really well explained. Would it be possible to have a video explaining the design of power cmc and dmc?

[@sambenyaakov]

Thanks for note and suggestion. This is a good subject, I might prepare a video on that.

[@learnelectronics6088]

Hi Professor, first of all thanks for such a great video.. I think that in 27:57 the DELTA-I you put into the n formula need to be 44A instead of 22A which is (DELTA-I)/2 correct? if so, we get twice turns which not feet into the given Aw what can be done in such a case ?

[@sambenyaakov]

Thanks for finding this inconsistency. Delta I and B are from zero to peak not peak to peak. I should have clarified this

[@seckisecen9445]

Thank you, you have provided very good informations.

[@sambenyaakov]

👍😊

[@Maduraikaran]

It was really nice video.. Thanks for posting it and looking ahead of more videos related on transformers. Thank you Regards, Sivaraman

[@sambenyaakov]

Thanks.

[@vasiliy5578]

When designing a powder core inductor it is always worth to check how permeability drops with DC-bias and then correct the number of turns accorinaly. I wonder if it holds for ferrite inductor design in practice? Some manufacturers (TDK) are providing data for relative reversible permeability changes within the DC magnetic field for different values of equivalent permeability (different gaps). So the question is whether it is worth it to check drop in permeability for particular design or limiting Bpk further from B saturation will make the job done?

[@sambenyaakov]

Since the permeability of aberrate inductor is approximately the ratio between magnetic path length and gap length, ferrite permeability has little effect until it collapse at the Curie temp.

[@sam7901]

Very useful Sir. I was only awarevof McCormick's method and frankly didn't find it very useful because it didn't account for saturation of the core. This method is more realistic and can give us a ball park number to do trade studies between ripple, interleaving, inductor size...

[@danielrobson9163]

is there a book or online resources that you could recommend that covers all of this in more depth?

[@sambenyaakov]

Sorry. I am not aware of such a publication. Thanks.

[@sagarmodi2040]

I have a doubt regarding the filling factor k. Usually the equation N*Aw=ku*Wa true for all inductors where (Aw= cross section area of winding, Wa = window area, ku =fill factor and N= number of turns). You have selected the number of turns by formula N=(L*delta_I)/(Ae*delta_B). It turned out to be 17. Now, if you calculate the fill factor using the above formula ku= (N*Aw)/Wa then it would be (17*10.4)/(44.4*12.1) that turned out to be 0.32. However, you assumed the ku to be 0.5. Which is the correct value of ku?

[@sambenyaakov]

This is a chicken and egg question😊 . In the design you assume an ku. Now you select a core. Chances are that it will NOT have the exact Aw you assumed. Obviously you select one with a larger Aw. This makes the effective ku smaller.

[@azharajiel8500]

Thanks so much professor for your lectures . I would like to know, how I can calculate R ac and R dc for planar magnetic core (flat magnetic)

[@azharajiel8500]

I mean resistance for Ac winding in inverter for planar inductor to calculate power losses in winding

[@sambenyaakov]

Rds is of course trivial. For Rac you might find some analytical approached on the web. I suggest FEA simulation especially for PCB windings.

[@GeethikaKilari-c7n]

Sir,I'm trying to design a 2.4mH inductor using E 42/21/15 core (taking EE set) for peak current of 2.5A, considering a winding factor of 0.4, I got 99 turns and air gap of 1mm , in the tdk datasheet the for the corresponding air gap of 1mm permeability =118,AL is 272 which gives a 2.6mH ,but if I tried to analyse the results using FEMM 4.2 keeping permeability as 118 ,I'm getting very less value,even after including the fringing factor which is 1.25 ,using the resulting permeability of 122 I'm still getting 1.7mH in FEMM ,can you please help me with this.

[@sambenyaakov]

The difference seem to be too large. Perhps due to the fact that the FEMM is two dimensional?

[@arianaescobar3640]

Really nice and interesting video Sam. I'm just wondering why on minute 21:38 you get B from the graph with 3F3 instead of 3C94?

[@sambenyaakov]

Oops, this is a glitch. Sorry. Thank for pointing this out.

[@JigneshPatel-ld2hq]

Hi Sam, @ 31:12 shouldn't the surface area be A= (65x65x2) + (65x27.4x4) = 15574 ? Also, can you please briefly explain how the units (mW/cm.sq.)^0.833 equate to °Cel.

[@sambenyaakov]

No. Just thew outside surface. An experimentally fit equation does not require unit matching

[@JigneshPatel-ld2hq]

I didn't understand the 65x3x4 part. The total does not match with 17680?

[@АлександрРиз-ф6к]

Sam, thank you for video! Please correct me if I wrong, in case of pure AC current on inductor, I should use for delta B = 2B(hat). So if I had picked 60 mT using P/v vs B graph, i must use 120 mT for delta B in Ap2 calculation? Thank you!

[@sambenyaakov]

Not sure I follow. Please indicate minutes in video you are referring to.

[@АлександрРиз-ф6к]

@@sambenyaakov At the 21:50 you mentioned that Bhat =deltaB/2 hence delta B = 2*Bhat. Then you calculate Ap2 at the 22:10 minute of the video, and for delta B substitute 2*Bhat. The question is: is it true that in the case of pure AC current on a choke without any DC, Ap2 is calculated in the same way? In another words, in case of AC with no DC bias, if i pick 60 mT at graph (21:50) for Ap2 calculations i using deltaB=2*60mT=120mT also.

[@sambenyaakov]

Thanks for clarification. Since I have formulated Ap2 as a function of DeltaI then the right value in equation is DelaB. In pure AC excitation, the swing of deltaB is related to the swing DeltaI same way and the losses are still a function of DeltaB/2

[@yingpang6366]

Hello Professor. Suppose you need to design for a PFC inductor, how could you choose then the delta B?

[@sambenyaakov]

Saturation or losses whichever is lower

[@yingpang6366]

Sam Ben-Yaakov I mean how to calculate the core losses now since the duty cycle would be changing and so are the current ripples