Types of Self "Power Inductors Universal Application"
Iron powder toroidal core chokes with single or double winding are primarily used in the applications where a significant attenuation of the symmetrical or differential interferences is required, i e between phase and neutral, together with a large independence of the inductance value from the current.
The interferences mentioned are typically produced by phase controlled electronic devices like triacs, thyristors, etc.
In the diagram, a typical power supply filter is shown, with a double winding IP core choke and the Cx capacitors:
The symmetrical interference suppression is granted if the two windings are connected in series, i e in such a way that the corresponding flux are added; thus also the symmetrical interferences generate a flux on both the windings which is added, and the full inductance is operative. In this case the inductance value is approx four times the single winding value.
In practice, the most communly used IP core chokes are realized with only one winding, with one or two capacitors, but the attenuation is clearly lower.
These filters are effective in spite of the strong magnetic field because the choke magnetisation, and so the inductance, is slightly dependent on the coil current.
If an effective filtering of symmetrical and asymmetrical interferences is required, both currentcompensated and IP chokes can be used.
List of family Power Inductors Universal Application