Shielded Enclosure
Shielding
If you wish to take into account the Magnetostatic Shielding Effect, in addition to the eddy current shielding, much more complicated formulas are required
Below are the calculated approximations for homogeneous magnetic field shown for housings with the dimensions
L1 = L2 = 300 mm and B = 400 mm
Calculated Shielding Effect Kurve 1: Mu-Metal 100 µm thickness µr = 80000 Kurve 2: Copper 100 µm thickness µr = 1
However, the Mu-Metal's excellent effect comes at a price: Like all high-permeability materials, Mu-Metal saturates even at comparatively low field strengths - and then has virtually no effect
The maximum permissible magnetic field strength follows from Hmax = Bmax / (μ0 μr)
Assuming a Bmax of 0.3 Tesla (for linear behavior) and μr of 80,000 gives a permissible Hmax of about 3 A/m
Whereas magnetic field strengths of up to 1000 A/m can be expected in the shielding area of power electronics
Calculated Shielding Effect Kurve 1: Steel 3 mm thickness µr = 300 Kurve 2: AlMgSi 6 mm thickness µr = 1
Despite the significantly better conductivity of the aluminum alloy (30 x 10^6 to 8.6 x 10^6 S/m), the steel shields better because of its magnetic property. Even with half the wall thickness, a higher shielding effect is achieved throughout.
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