# Mutual Inductance dot convention?

jean28
Could anyone give me a link that explains or simply explain to me how the dot convention on the mutual inductance works? For example, I'm trying to draw an equivalent circuit that converts the dots into voltage sources of this circuit:

http://i1226.photobucket.com/albums/ee410/jean28x/CircuitMutual.jpg

But I can't seem to figure it out completely. I think a voltage source can be put between I1 and I2 that delivers j2 * I2 volts and another one can be put after the j8 inductor that delivers j2 (I1 - I2) volts but I am not sure.

Thanks a lot!

## Answers and Replies

szynkasz
If current enters dotted terminal of one coil then positive voltage is induced at dotted terminal of the second coil. If current leaves it then induced voltage is negative.

jean28
If current enters dotted terminal of one coil then positive voltage is induced at dotted terminal of the second coil. If current leaves it then induced voltage is negative.

So according to that, if I do a KVL on the 3rd mesh I would get j6 (I2-I1) + 5 (I2) + j8 (I2) - j2( I1 - I2) - j2 (I2)?

Something like this:

http://i1226.photobucket.com/albums/ee410/jean28x/aac17e215cf907cd614a04bafdfd4775.jpg

szynkasz
1) Currents in both coils leave dotted terminals so voltage sources should have opposite polarization
2) Current enters the dot on L1 so "+" terminal of voltage source is on dotted terminal of L2 hence that voltage is negative

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jean28
1) Currents in both coils leave dotted terminals so voltage sources should have opposite polarization
2) Current enters the dot on L1 so "+" terminal of voltage source is on dotted terminal of L2 hence that voltage is negative

Ok i finally got it now. You have no idea how grateful I am for this. Too bad I learned it too late but hopefully I'll be able to apply it well for my next test.

Now, if I could only figure out how to simulate the circuit in the first picture in PSPice or MATLAB...

szynkasz
PSpice uses K part for coupled inductances.

LJLabuschagne
Thank you very much for your explanation.

Somehow it conveyed the concept better than any textbook.

Thank you!

Lezahn Meiring
Effective inductance dot convention

So just to make sure... if the current enters the coil at the dotted terminal..how exactly does that effect the other coil and it's dot regarding the mutual inductance...?