Series Inductance

Formula

Description

Inductors in series add directly, behaving like resistors in series. The total inductance equals the sum of individual inductances because the same current flows through each inductor and their magnetic fields add together. This simple addition assumes no mutual coupling between the inductors, meaning they are physically separated or oriented so their magnetic fields do not interact. If mutual inductance M exists between two inductors, the total becomes L1 + L2 + 2M (for aiding fields) or L1 + L2 - 2M (for opposing fields).

Variables

• Ltotal — Total equivalent inductance (H)
• L1, L2, ... Ln — Individual inductor values (H)

Practical Notes

In practice, place series inductors perpendicular to each other on a PCB to minimize mutual coupling. Toroidal inductors have self-contained magnetic fields and can be placed closer together without significant coupling.