K — Mutual Inductance

The mutual inductance statement defines magnetic coupling between two inductors.

Syntax

K<name> <L1_name> <L2_name> <coupling_coefficient> [M=<m>]

Parameter	Description
`L1_name`	Name of the first inductor
`L2_name`	Name of the second inductor
`coupling_coefficient`	Coupling factor k (between -1 and 1)
`M=m`	Multiplier

* Simple transformer coupling
L1 PRI_A PRI_B 10m
L2 SEC_A SEC_B 10m
K1 L1 L2 0.99

* Loosely coupled inductors
L3 A 0 100u
L4 B 0 100u
K2 L3 L4 0.5

For an ideal transformer, use a coupling coefficient close to 1.0. The turns ratio is determined by the inductance ratio:

$$n = \sqrt{\frac{L_1}{L_2}}$$

* 10:1 turns ratio transformer
L1 IN 0 100m
L2 OUT 0 1m
K1 L1 L2 0.999