INDUCTORS IN SERIES

As long as the magnetic fields around inductors do not interact, inductances in series add like resistances in series. The total value is the sum of the individual values. It is important to be sure that you are using the same size units for all the inductors when you add their values.
Suppose that you have inductances L₁, L₂, L₃,…, Ln connected in series (Fig. 1). As long as the magnetic fields of the inductors do not interact—

Fig. 1. Inductances in series add like resistances in series.

that is, as long as there is no mutual inductance between or among the components— the total inductance L is given by this formula:
L = L₁ + L₂ + L₃ + ... +L_n