MEANS OF NORMALISING THE LEVELS OF MAGNETIC FIELDS OF LOCAL SOURCES

Abstract

The protective properties of soft magnetic metal alloys for shielding ultra-low frequency magnetic fields have been investigated. The dependence of the shielding coefficients of industrial frequency magnetic fields by the most common electrical steels on the induction of the shielded magnetic field has been established. It has been determined that this dependence is non-monotonic. The presence of the maximum shielding coefficient is due to the achievement of the saturation induction of the material. The values of the shielding coefficients depend on the specific losses in steel, which are reference values. It has been shown that for the manufacture of shielding structures, it is advisable to use low-grade electrical steels, which are least suitable for their main application – the manufacture of cores and magnetic conductors. A two-layer structure is proposed for shielding highintensity magnetic fields, for example, in built-in transformers. A two-layer structure made of electrical steel with a gap between the layers has higher industrial frequency magnetic field shielding coefficients than several layers of the same steel. This reduces the weight of the shielding structure and increases its efficiency. Filling the gap between the layers reduces equipment noise, which is a regulatory parameter. The dependence of the magnetic field shielding coefficients of amorphous cobalt alloys on the induction of an external magnetic field has been studied. This dependence is non-monotonic, which must be taken into account in the design of shielding structures. Amorphous ferromagnetic alloys are also effective in shielding low-frequency magnetic fields. The advantages of such alloys are high magnetic permeability and low thickness. Thermomagnetic treatment of amorphous alloys significantly increases their protective properties. The feasibility of developing a composite material with a filler of finely dispersed amorphous soft magnetic alloy is shown.