How do I build a transformer model?

The best way would be to draft a model with coupled inductors with a mutual inductance statement placed as a SPICE directive on the schematic. See the section on mutual Inductance for more information. Inductors participating in a mutual inductance will be drawn with a phasing dot.

The following example demonstrates a transformer with 1:3 turns ratio (one to nine inductance ratio) with a sine wave input and simulates for 0.1ms. The K is set to 1 to model a transformer with no leakage inductance.