Shielding of High Magnetic Fields

This paper revisits the problem of shielding low-frequency high magnetic fields. Such fields are encountered in the domain of electromechanical energy conversion particularly during railgun operation. Using finite-element analysis, we investigate, separately, the mechanism of redirection of the magnetic flux due to induced eddy currents and the magnetic flux shunting due to highly permeable materials. In a first phase, various shapes of highly conductive shields are analyzed in the frequency domain. In a second phase, we study the shunt effect of different shields being made of magnetic materials. In a magnetostatic model afterward, for a shield that combines both highly conductive and magnetically highly permeable materials, the case of a double-exponential-shaped magnetic field is treated in the time domain. Finally, we make some remarks on the concept of shielding effectiveness.