With the exception of air-core coils, all power inductors possess certain saturation characteristics. That means inductance decreases with increasing levels of current. This is due to the various core materials, which start to lose their permeability more or less strongly after a certain induction level B is reached and in extreme cases take on the characteristics of air. The saturation characteristics of an inductor can be influenced by
- the type of core material
- the core geometry
- the number of turns
- and the air gap
However, there are often differences between the calculated inductance at a certain current (e.g. the rated current) and the real inductance, because:
- there are production spreads of the cores
- the data sheet specifications for the core are imprecise or incomplete
- the choke geometry causes an inhomogeneous field distribution
- manufacturing tolerances occur
- there are temperature influences
For this reason it is important to measure saturation characteristics during the development phase and quality inspection of power inductors.
On the following pages some sample applications will be presented.