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coupling factor

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New Member

simulating in pspice

I have this transformer circuit and i want to define the coupling factor K. How do I do that? I think i can do it from the netlist, but how do i make changes in it?


C_C1 N00313 N00283 1u
L_L4 N00791 0 2000H
R_R2 N00313 N00283 0.25k
R_R4 0 N00926 100MEG
R_R1 N00391 N00313 2k
R_R3 N02847 N00561 10
L_L3 N02847 N00926 0.01H
L_L1 N00283 N00791 0.5H
V_V2 N00391 0
+SIN 0 10 167 0 0 0
L_L6 N00926 N00561 20H

thanks for the help!
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Well-Known Member
Most Helpful Member
Hi there,

The way it looks like you are doing it the coupling factor would come in
with the choice of core such as K1 or K2. The net list for that would
look like this:
K1 L1 L2 0.90 CoreModel
K1 is the symbol for the core
L1 and L2 are the inductors that make up the primary and secondary
0.90 is the coupling factor
CoreModel is the actual model of the core being used and may appear
in a MODEL statement such as:
.MODEL 3B7 CORE (MS=342.012K A=15.0199 K=712.814M ALPHA=126.117U)
where the stuff in the parens are the params for the Jiles Atherton magnetic

If you dont do it that way, then you would need to construct your own
transformer using voltage and current sources and then use inductors on
the input and output. There should be much about this on the web that
tells how to do the transformer using the sources.
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That .model statement looked a little funny to me, I found out that ltspice doesn't support core modeling, oh well. I did however find this website which seems to have quiet a bit of information on it.

Magnetics - The Core Model


Well-Known Member
Most Helpful Member

Yeah, it's unfortunate that not all spices were created equal :)
Apparently some spices are spicier than others he he.

I was in a hurry so i didnt look up the transformer model i was talking about
which would be much simpler if he didnt need to model the core material.
A couple dependent sources does the trick.
If he comes back i'll look it up unless someone else feels like it before then.
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