In magnetic shielding with the opening of the magnetic material around the electric power line, I confirmed the difference of effect in various opening conditions by an experiment.
The results are as follows. The shielding effect was low under conditions of opening rate more than 30%. The difference by opening pattern was small, but the effect with the staggered pattern was high in a specific condition. By the method to increase area of each opening, the effect decreased in the neighborhood of the power line, but there was not the difference in the distant place.
