Chokes are air or iron core coils that operate as inductive reluctances. Chokes are used as current limiters as well as for producing parasitic fields. Those are made for 1 or 3 phase use.
In air-cored chokes the magnetic flux travels totally in air, so that the inductance is not dependent on current. Air-core chokes are used for high frequency applications.
When higher inductance values than are available from air core chokes are wanted, the choke is built around some kind of ferromagnetic core. In a low frequency solution, the used core material is usually transformer iron. Core types are same as used in our EI and UI type transformers. High power/frequency chokes are built to their own core types. The temperature class generally used is B.
When installing non-encased chokes it should be noted that stray magnetic fields can cause sounds in nearby metal devices. Due to the presence of an air gap, the inductance of an EI core choke will increase if installed directly on a magnetically conductive base such as iron.
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