EE213 - 03 - Analysis of magnetic circuits - example

This lecture presents an example to explain the procedure to analyze magnetic circuits.
Note: There is a calculation mistake. In question statement, relative permeability mu_r is 1500, however, all calculations are done with mu_r =2,000.
Course title: Electrical Machines
Course Link: • Electrical Machines
Magnetic circuit
Air gap
Fringing effect

[@kaursingh637]

this is the best lecture on internet= thank u sir

[@jazzysehgal7543]

Best solution!

[@user-em7vw8vk5h]

Well explained

[@r2_playz_wr452]

Nice explanation sir jii

[@mohamednorwarsame3734]

A ferromagnetic core with a relative permeability of 1500 is shown in Figure Pl-3. The dimensions are as shown in the diagram, and the depth of the core is 5 cm. The air gaps on the left and right sides of the core are 0.050 and 0.070 cm, respectively. Because of fringing effects, the effective area of the air gaps is 5 percent larger than their physical size. If there are 300 turns in the coil wrapped around the center leg of the core and if the current in the coil is 1.0 A, what are the flux values for the left, center, and right legs of the core? What is the flux density in each air gap?

[@jaggerhaskou6353]

Great video Dr. thanks

[@nwauluemmanuel1959]

but the reluctances when calculated with relative permeability of 1500 gives a different answer than what you got, you can only get those answers if you use relative P of 2000 ,so i am confused why 2000 instead of 1500

[@MAFarooqi]

You are right, the calculation are mistakenly performed with a different mu_r. However, the explained procedure is correct.

[@justinchizunda8742]

Sir why where you not subtracting the length of the air gap when you where calculating the reluctances of the left and the right limb?

[@MAFarooqi]

In the calculation of reluctance of the core, the length of the air gap has been intentionally ignored. The reason is, the air gap length is so small that it will not significantly change the mean path length and hence the reluctance of the core, rather it will only make the calculations a little bit more complex. You may verify this point by repeating all these calculations. If you want more precise calculations, you can definitely subtract the air-gap length to find the length of the core. However, for magnetic circuits, such approximations are generally allowed.

[@MrBelleblaas]

Very clear explained.🙃

[@borellio4528]

Thank for this video

[@aliHasan-db2tb]

thank you so much sir

[@anwarhossain-qx3nk]

Mashallah!!! great class.

[@MAFarooqi]

Thanks and welcome

[@ranjeet_sohanpal]

Thank you Sir!🙏

[@nkosilodumosibanda]

Thank you very much sir you've earned a Subscription 😁😊 I just don't understand why we take half the length(half of 7 in this case)

[@MAFarooqi]

The path length followed by different flux lines flowing through the core is different - those flowing through the outer side of core have larger path length and those flowing through the inner side of the cored have smaller path length. In the calculations, we take the average or mean path length. In the example, we divide 7 by two to get the mean path length.

[@mohammedharis7968]

Thanks a lot

[@danntambwat4266]

I think there is a mistake with this answer Sir. When getting the length of the right and left side you are doing 37+37+37. But the only problem is that you are ignoring the gap length. Because you need to get the sum of that operation above minus the length of the gap. But if you don't do that it's as if there is no gap involved. Check it out sir. I'm surprised no one has noticed that from the time you posted the video

[@MAFarooqi]

In the calculation of reluctance of the core, the length of the air gap has been intentionally ignored. The reason is, the air gap length is so small that it will not significantly change the mean path length and hence the reluctance of the core, rather it will only make the calculations a little bit more complex. You may verify this point by repeating all these calculations. If you want more precise calculations, you can definitely subtract the air-gap length to find the length of the core. However, for magnetic circuits, such approximations are generally allowed.

[@user-tw2sx7ky7z]

I don't know what the problem is but if I compute the exact thing you've written, I get a different value

[@MAFarooqi]

Please make your calculations with relative permeability equal to 1200.

[@Jack_lBlack]

Great video!! Keep it up sir!!

[@MAFarooqi]

Thanks a lot!

[@geenabenater7337]

Hello, hope you are well. For working out the flux in the left core, wouldnt we minus the flux in the right core from the total flux? so it should be 0.0004?

[@MAFarooqi]

You are right, the flux in the left limb is equal to the flux in the central limb minus the flux in the right limb. There are some calculation mistakes in the example. In larger air-gap, 0.0015 Wb and in smaller air-gap 0.0019 Wb.

[@mohammedshafayatzamilziaa2128]

sir, do you have any videos on AC circuit? loved your videos. Great work, sir.

[@MAFarooqi]

Not yet.

[@gianmarcogirardi9745]

Thank you very much for this content. Just one question. What would R_right and R_left have been equal to in case this conductor had been axial symmetric? Thank you very much.

[@MAFarooqi]

I am sorry that I have limited knowledge about axial symmetric conductors and therefore cannot answer this question. May be someone else on this forum can help you.

[@MrBelleblaas]

You are right. First thing I was thinking about was "Is the circuit not symmetrical?", but after having a better look at it I saw my own mistake😒

[@abugrifaustinaawumbun1685]

Wow

[@richardmanda8512]

Sir were are you getting 1.05 .....?....am really lost on this value

[@MAFarooqi]

If A is actual area and 0.05*A (5% of A) is the effect due to fringing, then total effective area will be A + 0.05*A = (1+0.05)*A

[@richardmanda8512]

@@MAFarooqi the best lecture on KZbin so far....thank you sir

[@lupulwedanny7757]

the Reluctance for left and right you forgot to subtract the air gap lengths on both sides

[@MAFarooqi]

In the calculation of reluctance of the core, the length of the air gap has been intentionally ignored. The reason is, the air gap length is so small that it will not significantly change the mean path length and hence the reluctance of the core, rather it will only make the calculations a little bit more complex. You may verify this point by repeating all these calculations. If you want more precise calculations, you can definitely subtract the air-gap length to find the length of the core. However, for magnetic circuits, such approximations are generally allowed.

[@justinchizunda8742]

And why did you multiply the area by 1.05 instead of 0.05?

[@MAFarooqi]

If A is actual area and 0.05*A (5% of A) is the effect due to fringing, then total effective area will be A + 0.05*A = (1+0.05)*A

[@justinchizunda8742]

@@MAFarooqi thank you sir now I understand!!

[@wahibal-hakimi6333]

Thank you Dr, but I think there are some mistakes in the R calculations

[@MAFarooqi]

Thanks. Can you please point out these mistakes so that I may correct these in future.

[@nathanhynes8063]

@@MAFarooqi when I plug in those values into my calculator, they do not give me the values you say they are. for example R_c should be 40059At/wb. Good video though. Thanks

[@MAFarooqi]

@@nathanhynes8063 Your are right, there is a calculation mistake. Thanks for the correction.

[@fathimahakeem4149]

@@MAFarooqi your calculations of the first Rr is wrong. You didn’t subtract the air gap from the length.

[@MAFarooqi]

@@fathimahakeem4149 In the calculation of reluctance of the core, the length of the air gap has been intentionally ignored. The reason is, the air gap length is so small that it will not significantly change the mean path length and hence the reluctance of the core, rather it will only make the calculations a little bit more complex. You may verify this point by repeating all these calculations. If you want more precise calculations, you can definitely subtract the air-gap length to find the length of the core. However, for magnetic circuits, such approximations are generally allowed.

[@relaxwithme4695]

Sir,can you add a video about transients in synchronous machines or a book about it

[@MAFarooqi]

The book by Chapman is the best for that purpose.

[@relaxwithme4695]

@@MAFarooqi sir, How to imagine electrical power as the average power of the sine form while the mechanical power of the load is constant, in power balance?

[@MAFarooqi]

@@relaxwithme4695 Are you asking it in connection with motors? The mechanical power of the load is also not constant, the load power is the product of torque and speed, P= tau*omega. If the torque is sinusoidal, the mechanical power will also be sinusoidal.

[@Robin-gg6om]

I'm a korean student. Your video is my porn. Your explanation make me pump my heart.

[@Bdr_Eldean_]

Allah bless you professor 🙏❤️

[@kyf6705]

Flux l should be 0.0004? 16:25

[@MAFarooqi]

In larger air-gap, 0.0015 Wb and in smaller air-gap 0.0019 Wb.

[@RajeshKumar-nv7bq]

Sir , is finding equivalent reluctance (s) In parallel magnetic circuit is same as finding resistance in parallel electrical circuit ..?

[@MAFarooqi]

Yes, the procedure is the same.

[@Acoustic_Mutale]

If you are here because of Dr. Zulu leave a like UNZA monk

[@user-me3qo9qt7u]

Please good explain how you reach to 1.05 in this problem?

[@MAFarooqi]

Effect of fringing is to increase effective cross sectional area. As indicated in the questions, this increase is by 5 percent. That is, after incorporating the effect of fringing, effective area will become A + 5/100 * A = (1 + 0.05)*A = 1.05 *A.

[@louisezero3129]

@@MAFarooqi where did the 1 came from sir?

[@MAFarooqi]

@@louisezero3129 if you take A common from the two terms, inside brackets you get 1 for the first term and 5/100 for the second term.

[@louisezero3129]

@@MAFarooqi would it be the same thing if it said that the area is increased by 5%?

[@MAFarooqi]

@@louisezero3129 yes, exactly.

[@ahmedeissa3216]

what is the 1.05???

[@MAFarooqi]

Effect of fringing is to increase effective cross sectional area. As indicated in the questions, this increase is by 5 percent. This factor of 1.05 is to incorporate this fringing effect.

[@richardmanda8512]

But how do you get the same 1.05...?

[@refilweramahlo8532]

i dont understand that part of dividing by 100

[@MAFarooqi]

The lengths are provided in centimeters (cm), to convert cm into meters (m), lengths are divided by 100.

[@refilweramahlo8532]

@@MAFarooqi ok sir i get u can u do a video without a percentage

[@MAFarooqi]

@@refilweramahlo8532 Do you mean analysis of magnetic circuit without the effects of fringing? Lecture 2 presents analysis of a relatively simple magnetic circuit without fringing effect. It is shared at the following link. kzbin.info/www/bejne/sH_Pnnafi7mbeJY

[@mohamednorwarsame3734]

Dr. What is wrong? Your answer is not correct

[@MAFarooqi]

The value of mu_r is mistakenly taken to be equal to 2000 instead of 1500 in these calculations, therefore, these reluctances have different values. However, the explained procedure is correct.

[@loupejr.fuentes7815]

Your Rr is 120178.22 it is not 90100

[@MAFarooqi]

You are right, there is a calculation mistake.

[@loupejr.fuentes7815]

@@MAFarooqi I humbly observed that all of the reluctance if recalculated, it is not the same on the video. But I am still thankful to this channel

[@MAFarooqi]

The value of mu_r is mistakenly taken to be equal to 2000 instead of 1500 in these calculations, therefore, these reluctances have different values.