Electromagnetic shielding

QuickField simulation example

Uniform external magnetic field is produced by the electric magnet. The shield with the measuring coil inside is placed between its poles. EMF in the coil is measured: in case of DC current in the coil - by ballistic galvanometer (in the moment of switching on), in case of AC current - by use of voltmeter.

Geometry
The shield consists of two halves. The gap could be enlarged up to 2 mm by sheets of non-magnetic materials.

Given
Electrical conductivity of copper 57 MS/m.
Electrical conductivity of steel 10 MS/m.
Relative magnetic permeability of steel μ=1000.
External magnetic field flux density B = 0.139 T (peak value for AC magnetic problem).

Task
Find the level of magnetic field reduction inside the shield. Shields made of steel and copper of the same geometry are analyzed.

Solution
Due to symmetry of the model the simulation domain is requced to a quater of a full model.
External magnetic field is specified by the boundary condition A=0.0695 Wb at the top boundary.

Results
Current density in cylindrical and spherical shielding:

Shielding coefficient - relation of magnetic flux densities outside and inside the shield.

• Video: Electromagnetic shielding. Cylindrical shield. Watch on YouTube.
  
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