These chokes are widely used for differential mode disturbance suppression and as storage chokes in switching power supplies having switching frequencies up to 50 [kHz]. Typical applications are suppressing disturbances from switching thyristor circuits, dimmer switches, solid state relays, etc. Usually these disturbances are under 1 [MHz].
The chokes comprise of an iron powder toroid core with single winding. In comparison to a ferrite core the induction value is lower. Depending on the size and material of the toroid the chokes’ current causes partial saturation which reduces the inductivity. Therefor the nominal rated inductance is the inductance without operating current. Parasitic coupling over the windings is not important when concerning low frequency differential mode disturbances. This allows the use of several winding layers which in its turn creates space saving solutions.