Question in RDH4

[pdf64]

I've not tried a Hotplate, but can highly recommend a Fluxtone speaker for listening to the impact of such changes at domestic friendly sound pressure levels.
Pete

[Alan0354]

I have a question in cpt 5 p210.

Is Ls and L0 depending on the u of the core?

[J M Fahey]

Please cut and paste the page you are asking about.
Thanks.

[Steve Conner]

+1, my RDH4 is in a box in the attic right now.

[Austin]

I used the snipping tool..

[J M Fahey]

I have a question in cpt 5 p210.

Is Ls and L0 depending on the u of the core?

I think not.
As I understand it it depends only on the copper turns , in a way "as if they were an air core inductor".
That way, using a higher mu core with less turns maintains low frequency inductance but decreases high frequency one because of reduced actual turns. <-- please do not nitpick on my terms, it's a simplified explanation.
If high frequency inductance did depend on core permeability, you would gain nothing .... and it's not the case.

[Steve Conner]

L0 is the magnetising inductance, so it certainly is directly proportional to the core permeability.

Ls, the leakage inductance, isn't, to a first approximation. However, in a second-order approximation, the higher mu is, the smaller Ls will be for a given configuration of windings. A more permeable core actually decreases the leakage inductance.

The argument goes as follows:

The core threads all of the windings.
Any flux that travels in the core will also thread all of the windings.
The higher mu is, the more attractive a flux path the core is compared to air.
Therefore, the higher mu is, the more of the total flux will thread all of the windings.

(For completeness, I should say that leakage inductance is a result of flux threading one winding but not the others.)

[Alan0354]

L0 is the magnetising inductance, so it certainly is directly proportional to the core permeability.

Ls, the leakage inductance, isn't, to a first approximation. However, in a second-order approximation, the higher mu is, the smaller Ls will be for a given configuration of windings. A more permeable core actually decreases the leakage inductance.

The argument goes as follows:

The core threads all of the windings.
Any flux that travels in the core will also thread all of the windings.
The higher mu is, the more attractive a flux path the core is compared to air.
Therefore, the higher mu is, the more of the total flux will thread all of the windings.

(For completeness, I should say that leakage inductance is a result of flux threading one winding but not the others.)

I think the only way the book is correct is Ls independent to u AND L0 dependent on u.

This is how I work it out to proof what the book said.



(1) Gives the relation of inductance with different u if you use the same size core with identical cross section area S.

(2) Shows L0 is kept constant. Then if you increase the u, you can decrease the N from the formula given.

(3) show if you use (2) to keep L0 constant when increase the u, you lower the N. Since Ls independent to u, the Ls will decrease with decrease in N.


Also, I can see L0 depends on u. But what is the reason Ls not depending on u?

[Alan0354]

[ATTACH=CONFIG]20126[/ATTACH] I used the snipping tool..

How do you post this? If I were to do it, I would have to print the page out, scan into jpg, upload into Tinypic and link here!!!

Does this forum support Latex type of equation writings?

[Alan0354]

+1, my RDH4 is in a box in the attic right now.

How can it be in the attic?!!! I think this is one of the best reference book even though it's a cook book. I print out the chapters as I study and I keep it in my special book shelf in the family room together with a very few chosen ones like Field and Wave EM by Cheng, Microwave Engineering by David Pozar, Intro to Electrodynamics by D. Griffiths, Antenna Theory by Balanis and Partial Differential Eq by Strauss etc. It is that good in my opinion. Again, thanks Enzo.

[Alan0354]

I have found an article that explain L0 and Ls.

http://www.geofex.com/article_folder...es/xformer.htm

L0 is inductance measured across the primary when secondary is open.

Ls is inductance measured across the primary when secondary is shorted.

[J M Fahey]

I have found an article that explain L0 and Ls.

http://www.geofex.com/article_folder...es/xformer.htm

L0 is inductance measured across the primary when secondary is open.

Ls is inductance measured across the primary when secondary is shorted.

Well, Ls is what I called "high frequency inductance" because it mainly affects at high frequencies.
Conversely, I called Lo "low frequency inductance" because there's where it's important.
I guess everybody understood what I meant, but clarifying things never hurts.

As of snipping from Adobe Reader, one of the selection tools is called Snapshot and shows a little camera.
You select part of what you see on screen and it "clicks" (like a camera), captures what was selected and copies it in the clipboard.
You can paste it in any graphics software (I use Free IrfanView) and save it in any format you wish.
If possible avoid JPG, which is meant for holiday or family colour pictures and such (no kidding), .gif or .png are much sharper.
Once saved you do as you please, either attach straight here or upload somewhere else.
NOTE: sometimes PDF are "secured" and do not allow graphics cut and paste or snapshot; in that case you zoom in to fill the screen with what interests you, capture the screen and paste it into IrfanView , then do what you want (crop/sharpen/grayscale/resample/whatever).

[Austin]

How do you post this? If I were to do it, I would have to print the page out, scan into jpg, upload into Tinypic and link here!!!

Does this forum support Latex type of equation writings?

You go start menu-> all programs-> accessories-> "snipping tool" then drag a box around anything on your desktop you want, then save the pic somewhere like your desktop. Program is a feature in Microsoft Windows Vista or later, but there are third party apps that may offer the same functionality.
Also you can press "windows key" + "PrtSc" (print screen) button, then open paint and go to edit menu and click "paste" then save the image.



I agree about the Radiotron book, it is awesome! But I wish it was even more in depth about some of the oddball things that it makes reference to, it sometimes gets me excited then leaves me hangin'..

[Alan0354]

I have another question on page 211 cpt 13. This is to calculate the number of turns needed to get -1dB at 50Hz. The requirement is Rp=50ohm. So L0=2R/(2\pi f)=0.32H.

But then, the book gave magnetic path l =4.5" and cross sectional area A=0.56 sq in.

Then gave L0=(3.2AuN^2)(10EE8Xl)!!!

Can anyone site article how they arrive to this formula? also, what is the magnetic path l? I assume A is the cross section area of the coil.



Thanks Austin, this is my first attached image.

[Alan0354]

I have another question on page 211 cpt 13. This is to calculate the number of turns needed to get -1dB at 50Hz. The requirement is Rp=50ohm. So L0=2R/(2\pi f)=0.32H.

But then, the book gave magnetic path l =4.5" and cross sectional area A=0.56 sq in.

Then gave L0=(3.2AuN^2)(10EE8Xl)!!!

Can anyone site article how they arrive to this formula? also, what is the magnetic path l? I assume A is the cross section area of the coil.

[ATTACH=CONFIG]20136[/ATTACH]

Thanks Austin, this is my first attached image.

I figure this one out already, 3.2EE-8 is just u0 in inches.