Effect of magnetic pickups on the input transformers of measuring devices

Summary

The asymmetry coefficient δ for all types of transformers depends on the core permeability, which in turn depends on the ratio ofl _av/√s or D_av/√s. In order to reduce core permeability, it is necessary to select toroidal cores with a small diameter and a large cross section, and provide laminas of O-shaped and shell-type cores with a shape to make these cores short and large in cross section.

Under actual operating conditions, transformers with toroidal cores provide a higher immunity from noise. For the same designs, sizes, and relative parameter dispersions, the transformers with toroidal and O-shaped cores have a ratio of δ_max equal to 1.6. In shell-type transformers it is imperative to take into account the polarity of their windings on which the transformer's noise stability depends to a great extent.