Inductor and Transformer Design Equations

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I thought it would be a good idea to write this down, all in one place, finally.
Any errors, or impovements needed? Should it be in gaussian units?
 

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stewartcs

Science Advisor
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I thought it would be a good idea to write this down, all in one place, finally.
Any errors, or impovements needed? Should it be in gaussian units?
A .pdf would be better to thwart off any virus suspicions!

CS
 

berkeman

Mentor
54,312
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I thought it would be a good idea to write this down, all in one place, finally.
Any errors, or impovements needed? Should it be in gaussian units?
What does this mean?

N – number of turns, Fingers
What's a Fingers? I don't think I've ever see units on the number of turns.

Overall looks good, very similar to my transformer/inductor crib sheet. It could use some diagrams showing flux and such, and should include the impedance transformation characteristic (goes by turns squared) of a transformer.

Do you do crib sheets for other subjects/topics as well? My crib sheet binder gets a lot of use.
 
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I would be very interested in seeing other engineer's crib sheets. My notebook is pretty bare (non-existent).
 

berkeman

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I would be very interested in seeing other engineer's crib sheets. My notebook is pretty bare (non-existent).
Interesting idea! Maybe scan our crib sheets and share them to generate ideas. I like that.

Let me work on that some.... Cool idea. Maybe a Crib Sheets sub-forum here at the PF...
 
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4,209
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What does this mean?
Do you mean the Gaussian units? There are changes in some equations by a a couple factors.

I haven't done this in a while, maybe it was

[tex]v=N \frac{d\Phi}{dI}[/tex]
that becomes
[tex]v=N \frac{d\Phi}{dI} \cdot 10^{-8}[/tex]
in going from SI (kilogram-meter-seconds) to Gaussian units (essencially cgs. centimeter-gram-seconds)

I should check with some core manufactures to see what the prefered units are.

What's a Fingers? I don't think I've ever see units on the number of turns.

Overall looks good, very similar to my transformer/inductor crib sheet. It could use some diagrams showing flux and such, and should include the impedance transformation characteristic (goes by turns squared) of a transformer.

Do you do crib sheets for other subjects/topics as well? My crib sheet binder gets a lot of use.
I have notes buried within job folders, and never really concatenated them.
You know. One finger, two fingers, three fingers... That's how you count turns, right?
:smile:

I think PF crib notes would be a very good idea. Would it be better to associate with each forum folder, or all in one place--under mirrored subfolders, maybe?

Oh, by the way, the Turns squared increase in inductance is in there--the last equation. So I'll label it as such.
 
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berkeman

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I was curious about that. How do you convert .doc to .pdf?
You can download a free conversion utility from PrimoPDF.com

It installs like a printer driver, so it shows up when you do "Print" from a software package (like Word or Excel) -- you choose to print to PrimoPDF instead of a printer, and it "prints" to a PDF file.
 
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Thanks, berkeman. I got it loaded.


Bobbin cores and rod cores are difficult to solve, but a gapped core is not too difficult if you can guestimate the magnetic field fringent around the gap. But is the H field the same around the magnetic circuit given constant area. I'd been assuming it is in previous designs, with the results as expected, but is it true?
 

berkeman

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Thanks, berkeman. I got it loaded.


Bobbin cores and rod cores are difficult to solve, but a gapped core is not too difficult if you can guestimate the magnetic field fringent around the gap. But is the H field the same around the magnetic circuit given constant area. I'd been assuming it is in previous designs, with the results as expected, but is it true?
I believe so as well, as long as the area is constant.
 
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I got this out of Wikipedia (Maxwell's Equations),

[tex]\oint_{\partial S}B \cdot dl = \mu_0 I_S [/tex]

in the absense of electric fields, where

[tex]B=H\mu[/tex]

I'll have to mull it over a little just to be sure it fits....
 
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