Iron core

An iron core, also called a magnetic core or magnetic core, is a component for producing inductance, a property that has electrical circuits or components such as coils. It is therefore also used in transformers. Electromagnetic induction causes an electric field by changing the magnetic flux density.

What does induction in physics mean?

When an electrical conductor (e.g., coil) is moved perpendicular to the field lines of a magnetic field, an electric voltage, the induction voltage, is produced between its ends. This is caused by the Lorentz force, which acts on the electrons inside the conductor. A change in the magnetic field surrounding the coil has a direct influence on the induction voltage. According to the law of induction, the induction voltage is greater:

  • The faster the coil moves in the magnetic field
  • The stronger the change of the broad magnetic field is
  • The faster the magnetic field changes

To generate electromagnetic induction, the magnetic field of a permanent magnet or electromagnet can be used. How strong this voltage is, depends primarily on the type of coil, so:

  • Depending on the number of turns of the bobbin
  • Depending on the size of the cross-sectional area of ​​the coil

If the induction coil has an additional iron core, the magnetic strain is significantly higher.

What is an iron core?

A magnetic core does not necessarily consist of iron, as the name would suggest. Rather, all soft magnetic materials that have a high saturation magnetic flux density and a high magnetic permeability can be used. When current flows through the electrical conductor of the coil, the resulting magnetic flux can be bundled with little loss. Possible materials are:

  • Ferromagnetic metal alloys in sheet or powder form (electrical sheet or metallic glass, ie amorphous metals)
  • Oxide-ceramic ferrimagnetic substances (ferrites from iron oxide or magnetite)

The low residual magnetism is necessary so that the least possible voltage is lost during the reversal magnetization in AC operation. Iron cores made of electrical steel reduce by mutual isolation so-called eddy current losses, ie that current in an inhomogeneous magnetic field, which results from the temporal change of a magnetic field. In the case of direct current, however, unbleached, ie. use massive iron cores.


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