Overview
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When magnetic materials, such as steel sheets, are moved towards a magnet,
they are attracted mutually. The attractive force between the magnet and
the magnetic material and between the electromagnet and the magnetic material
has been efficiently used for motors and solenoids.
This note presents the use of magnetic field analysis to evaluate the attractive
force between steel sheets and a magnet. |
Attractive Force Characteristics for CASE 1
The magnetic flux density distribution for CASE 1 is shown in Figure 1,
and the attractive force is shown in Figure 2. The attractive force in
the Y-axis positive direction is set to be positive.
The magnetic flux is symmetrical due to the relative position between the
magnet and the steel sheets. The force is equally applied to the top and
bottom steel sheets but no force is applied to the magnet. |
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Attractive Force Characteristics for CASE 2
The magnetic flux density distribution for CASE 2 is shown in Figure 3,
and the attractive force is shown in Figure 4. In Figure 4, (4) is the
sum of the forces that work on the (2) magnet and the (3) bottom steel
sheet. The attractive force in the Y-axis positive direction is set to
be positive.
The magnet is attached to the bottom steel sheet in CASE 2, so the magnetic
flux density is higher at the bottom steel sheet than at the top steel
sheet. The attractive force is stronger between the magnet and the bottom
steel sheet than between the magnet and the top steel sheet. As a result,
the attractive force of the magnet is directed towards the negative direction,
and the sum of (1) and (2) is equal to (3). Also, (1) and (4) are equal,
indicating that the attractive forces on the magnet and on the bottom steel
sheet are calculated correctly. |
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