The transformer is a two port. The left port voltage v1, left port current i1, right port voltage v2 and right port current i2 are connected by the following relation:
         | v1 |         | L1   M  |  | i1' |
         |    |    =    |         |  |     |
         | v2 |         | M    L2 |  | i2' |
L1, L2, and M are the primary, secondary, and coupling inductances respectively.