These chokes are made of a single winding over a high permeability toroid core (ferrite) and show a high inductance at zero or low current, but a low inductance at the nominal current, because of the core saturation.
Such chokes are mainly used as line filters and noise suppression chokes in appliances where an inductive load is driven by a phase controlled device such as triacs, thyristors etc (e g motors).
When this device swítches on, the current aims to rise quickly with a verv steep front, so generating a high number of harmonics and thus a strong electrical interference of symmetncal type, i e appearing between phase and neutral.
The high choke inductance at the start of the current flow limits the current pulse steepness and so the harmonics, while as the core saturation occurs, its effect on the circuit becomes negligible: the inductive load itself contributes to reduce the disturbances.
The filtering effect is more effective if the choke is placed close to the interference source and it is also enhanced by adding a shunt capacitor.
List of family Saturable Noise Suppression Chokes
