Magnetic flux
The magnetic field channelled by the core, the carrier of coupling between windings.
Definition
Magnetic flux, denoted Φ and expressed in webers (Wb), represents the amount of magnetic field passing through a surface — typically the cross-section of a transformer core. It is the physical carrier that conveys energy from the primary to the secondary.
Created by the primary current, the flux is channelled by the magnetic circuit (the core) so as to maximise the part that passes through the secondary. A well-guided flux means good coupling and high efficiency; flux that “leaks” out of the core forms the leakage flux, responsible for the leakage inductance and part of the impedance.
The flux value depends on the applied voltage and the frequency, but not on the load: a transformer works at nearly constant flux from no-load to full load.
The ABL tip
Poorly channelled flux radiates and can disturb nearby sensitive electronics. For critical environments (audio, instrumentation, medical), ABL Transfo offers toroidal cores and shielding that confine the flux.
