# Calculate mean path length of a magnetic circuit

1. Oct 3, 2015

### TheRedDevil18

Given this magnetic circuit:

With these dimensions:

With this equivalent circuit:

If I am using F = HL to calculate the mmf drops in RcoreAB(see equivalent circuit) and RcoreBCDA(see equivalent circuit) then how would I calculate L in the formula ?

2. Oct 3, 2015

### Hesch

You have two loops ( left/right ). For the left loop you will have the drawn path length:

Liron + Lair
Lair = 2s.

In air the permeability is μ0, and in iron the permeability is μ = μ0r.

The mean length is the length of the drawn path. So you could ask: What is the mean permeability in the loop ?

3. Oct 3, 2015

### Hesch

#2: Figure comes here:

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4. Oct 3, 2015

### TheRedDevil18

So can I just sum the path directly in the middle of the loop or lamination ?, I heard that the center of the core is where the flux travels the most

5. Oct 3, 2015

### Hesch

Yes, as the dashed lines in the figure indicates.

I think the flux will be spread almost equally in the cross section area of the core.

It cannot be calculated precisely anyway, because the practical μr for iron depends on the direction wherein the iron plates have been rolled: A flux direction parallel to the roll-direction results in the greatest μr. But then there is a problem with the corners of the core, where the flux must change direction, crossing the roll-direction.

PS: You mean the center leg? Yes of course: double up. But normally the center leg has the double cross section area as well ( compared to the left/right leg ).