# Inductor and Transformer Design Equations

1. Mar 17, 2009

### Phrak

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?

#### Attached Files:

• ###### Transformer Equations.doc
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2. Mar 17, 2009

### stewartcs

A .pdf would be better to thwart off any virus suspicions!

CS

3. Mar 17, 2009

### Staff: Mentor

What does this mean?

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.

Last edited: Mar 17, 2009
4. Mar 17, 2009

### Corneo

I would be very interested in seeing other engineer's crib sheets. My notebook is pretty bare (non-existent).

5. Mar 17, 2009

### Staff: Mentor

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...

6. Mar 18, 2009

### Phrak

I was curious about that. How do you convert .doc to .pdf?

7. Mar 18, 2009

### Phrak

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

$$v=N \frac{d\Phi}{dI}$$
that becomes
$$v=N \frac{d\Phi}{dI} \cdot 10^{-8}$$
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.

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?

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.

Last edited: Mar 18, 2009
8. Mar 18, 2009

### Staff: Mentor

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.

9. Mar 18, 2009

### Phrak

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?

10. Mar 18, 2009

### Staff: Mentor

I believe so as well, as long as the area is constant.

11. Mar 19, 2009

### Phrak

I got this out of Wikipedia (Maxwell's Equations),

$$\oint_{\partial S}B \cdot dl = \mu_0 I_S$$

in the absense of electric fields, where

$$B=H\mu$$

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

Last edited: Mar 19, 2009