POWER EFFICIENCY OF EDDY-CURRENT SHIELDING OF STRUCTURAL-STEEL IN TRANSVERSE MAGNETIC-FIELD

This paper analyses the power efficiency of eddy current shielding of structural members from the field produced by the nearby cables. A two dimensional geometry is used for illustration. Power loss in the structure, in the absence of the shield, is compared with the aggregate power loss in the structure and in the shield when the shield is present. Results show that eddy current shielding is power efficient only when the dimension of the shield is smaller than a certain characteristic length. A criterion is proposed to assist the estimation of this characteristic length. It depends on the dimensions, the magnetic permeability, the conductivity of the structure to be shielded and the operating frequency. In the case of nonmagnetic conductors, the effect of an eddy current shield is to reduce the power loss in the object. But the aggregate power loss does not decrease.