Hum of magnet cores and determination of the magnetostriction of FeSi electrical steel

A cause for humming noises of reactance coils, transformers and other magnet cores can be among other things

• electromagnetic forces between the individual laminations of the cores
• forces between the front surfaces of the magnetic circuit in the air gaps
• magnetostrictive length variations of the ferrousmagnetic core material
• couplings between the magnet core and magnetic construction parts by scattering fields
  

In a special case intensified humming could be assigned clearly to a material substitution. The noise increased at the same time with the use of a new electrical sheet quality as core material. For this reason the work was concentrated on comparative investigations of the electrical steels.
It was examined

• the magnetic characteristic values of the electrical steels
• the magnetostrictive length variations

Because of the different magnetization conditions in the specimens the results of measurements will can not transfer easily to the behavior of the material in the core. From the magnetostriction and the punching behavior resulted that of the new electrical steel was the cause for humming.

On the influence of different time function B(t) of the flux density B in the magnet core is reported during the representation of a further work.

Because of parallel to a material substitution the humming noises of a ballaste core increase the magnetostriction of the electrical stelles was examined in detail.