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
where
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
model.
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.