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I can't find an explanation for something and I thought I'd come and ask you.

I'm studying for a test I have tomorrow and I came across a problem of a three legged steel core with 400 turns on the center leg, the magnetization curve is given, the first part of the problem asks you to find the current required to produce a certain flux density in the central leg of the core.

So what I did was to first find the magnetic flux across the leg.

Φ

_{center}=B.A

_{cross}

Then because the two outer legs are symmetric, I found their magnetic flux by dividing the one coming from the center leg, and found the flux density on each outer leg with this information.

B=Φ

_{outer}/(A

_{cross}

But then, when trying to find the MMF, for me, it would be the MMF required to produce that magnetizing intensity on the center leg plus the magnetizing intensity on each outer leg so what I did was:

*F*H*l

_{total}=_{center}+H*l

_{outer}*2

but checking the Instructor's manual, it only takes in consideration the magnetizing intensity for the center and one leg (one magnetic loop):

*F*H*l

_{total}=_{center}+H*l

_{outer}

I guess it's because of the analogy with electric circuits when they are in parallel, but I'm not sure, so I was wondering why is it we only take one of the outer legs in consideration, instead of the two of them to find the total MMF.

Can anybody enlighten me? I'd appreciate it! Thanks in advance!

The problem is 1.13 in Chapman Electric Machinery

https://imgur.com/a/PD8A7xQ