The shielding effectiveness of steel enclosure for pulsed magnetic field

By global analysis of the generator, the loop antenna and the shielding enclosure with FDTD method, the small-loop, approach for measurement of the magnetic field shielding effectiveness was simulated numerically in this paper. Non-uniform meshes and Reduced c FDTD Method were adopted to solve the contradiction of selecting space step and time step, this makes it possible to calculate the steel shielding efficiency of large dimension. The interaction of shielding enclosure and loop antenna was modeled. The setup of the simulation coincides with the real condition of engineering testing. The conclusions from the numerical calculation are: The waveform of EMP transparent though the steel shielding enclosure is greatly different with the incident EMP waveform. The rise time changes to be very slow and the width of pulse gets long. The calculating and real testing indicate that the shielding efficiency of steel enclosure to the EMT with longer rise time(mus) and wider duration(1ms) is only about 40dB, the rise time of transparent pulsed magnetic field reaches ms and the pulse width is more than 10ms. The shielding efficiency of the steel enclosure to low frequency electromagnetic field is much lower.