At 50 - 60 Hz, you are in the near field, so you need to consider electric and magnetic field shielding separately. Also, at these frequencies, shielding is not really a matter of reflection and absorption. It's more a matter of locally redirecting the fields. Electric-field shielding can be done with good conductors, but magnetic field shielding will require that you either:
1. Use a material with a high permeability such as steel to redirect the field, or
2. Design a conductive shield that reroutes the currents responsible for creating the original magnetic field.
In typically applications, non-magnetic materials like copper or aluminum have virtually no effect on low-frequency magnetic fields.
Highly conducting metallic enclosure of sufficient thickness can be used to shield the test specimen from electromagnetic waves which will be absorbed by the metal.Thickness of metallic cover should be more than penetration depth which depends on the conductivity of the metal used, frequency of e. m wave and permeability of the metal.
At 50 - 60 Hz, you are in the near field, so you need to consider electric and magnetic field shielding separately. Also, at these frequencies, shielding is not really a matter of reflection and absorption. It's more a matter of locally redirecting the fields. Electric-field shielding can be done with good conductors, but magnetic field shielding will require that you either:
1. Use a material with a high permeability such as steel to redirect the field, or
2. Design a conductive shield that reroutes the currents responsible for creating the original magnetic field.
In typically applications, non-magnetic materials like copper or aluminum have virtually no effect on low-frequency magnetic fields.
Really, electric field shielding is not a problem. As for magnetic field, full shielding could be perform by using superconductor. Usual ferromagnetic material with high conductivity and high permeability is suitable in some cases, but could require thick and heavy construction.
In my opinion active shielding with correct oriented coils and small currents could be useful for shielding of 50-60 Hz magnetic fields.
Dear Sir,
this is the question of the field source. If ew have a magnetic 50 Hz source field , we must shield with a magnetic permeability material like mu metal or Fe or ferrite. If we have a 50 Hz electric field we must use a good metal with a high conductivity like Ag ,
Cu, ...
Yours Sincerely
Thank you all.
Mr Korkut has added good point. I wish to add / ask, how does it vary with respect to frequency!
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