The ferromagnetic shields represent an effective solution for the time constant and low frequency magnetic fields attenuation. This paper presents an efficient method for evaluation the ferromagnetic shielding. It needs the computing of the time-periodic eddy currents in nonlinear media. Using the Polarization Fixed Point Method and the Fourier decomposition of the time-periodic magnetization, the electromagnetic field is obtained by solving the eddy-current integral equation for each harmonic. The magnetic field in shielded zone is produced by the imposed current distribution, the induced currents and the magnetization of ferromagnetic bodies, the integral equation is applied only on the shield domain which occupies a very reduced space or, if other conducting bodies are in the vicinity of the shield, the integral equation is extended only for them. The system matrix is inverted only once, before the iterations and remains unchanged.

Keywords: Eddy current integral equation, Ferromagnetic shield, Fourier analysis, Nonlinear periodic fields, Polarization fixed point method, Shielding efficiency