Leakage inductance
The uncoupled flux between windings, the source of the impedance.
Definition
Leakage inductance reflects the share of magnetic flux that is not shared between the primary and the secondary: this “leakage” flux closes through the air or surrounding materials instead of passing through the other winding. It behaves like a series inductance in the circuit.
It is the main contributor to the transformer’s short-circuit impedance (Ucc %). A high leakage inductance naturally limits short-circuit currents — useful to protect the downstream network — but degrades voltage regulation. Conversely, very tight coupling gives low leakage and excellent regulation.
It depends on the winding geometry: layout, interleaving and distance between primary and secondary.
The ABL tip
Leakage inductance is a design lever: you increase it to limit fault currents, you reduce it for precision. Tell us your priority (protection or regulation) and we adjust the winding geometry.
