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Attraction of the cylindrical magnet to the steel plate

Cylindrical permanent magnet is pulled toward the ferromagnetic plate.

Problem type:
Axisymmetric problem of magnetostatics

Geometry:

D = 2" (50.8 mm) - magnet diameter;
l = 0.65" (16.51 mm) - magnet thickness;
t = 2" (50.8 mm) - plate thickness;

Given:
magnet grade N35, Hc = 954930 A/m, Br = 1.26 T;
relative magnetic permeability of plate μsteel = 1000.

Calculate the pulling force of the magnet toward the steel plate.

Solution:
To calculate the pulling force accurately, and avoid integration along the edge dividing media with large difference in magnetic permeabilities, we place the magnet at a small distance δ = 0.005" (0.127 mm) from the steel plate. Integration contour is drawn in the air around the magnet.

Result:

 Pull force QuickField 542 N Reference* 510 N (112.3 lb, 1 lb = 4.54 N)

* Reference: www.kjmagnetics.com.

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