Protection Against Exposure to DC or AC Magnetic Field Based on Partial Shielding

Abstract

With the advancement of technology, it is becoming increasingly necessary to protect electrical devices from electromagnetic fields. For this reason, it is important to analyze how an electromagnetic field can be reduced. This paper examines shielding as a way of reducing magnetic fields. The reduction can be achieved by various shield geometry, placed coaxially with a long current carrying wire, in order to decrease the magnetic field outside the shield. DC and low-frequency AC fields (50 Hz) shielding are investigated. For the DC fields, a shield made of a high permeability ferromagnetic material was applied, while for the AC fields, a copper layer of different thicknesses was added to the ferromagnetic material to reduce the magnetic field more effectively by the currents induced in it. Shielding effectiveness as a parameter applied to quantify the shielding quality was calculated for different combinations of shading material thickness and arc length. The most significant increase in shielding effectiveness occurs at the thickest copper layer, between the shield angles 180 and 270 degrees. At the distance of 565 mm from the system axis, the shielding effectiveness will increase 2.4 times for the specified angle increase. The obtained results show that partial shielding can provide good protection in many practical cases and additionally reduce the amount of used material.