Overview
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A solenoid valve is a device that opens and closes the valve by moving
a plunger using electromagnetic force. Upon considering the effect of the
fluid stress caused by opening and closing the valve, it is important that
the attractive force is proportional to the drive current, and that a constant
attractive force is obtained regardless of the position of the iron core.
This note presents the use of magnetic field analysis to obtain the attractive
force of a solenoid valve at different positions of an iron core. |
Magnetic Flux Density Distribution
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Figure 1 shows the magnetic flux density distribution at different movable
core positions. The closer the movable core moves toward the stator core,
the smaller the air gap becomes. So, the magnetic flux increases in the
moving direction and the magnetic circuit changes. The magnetic circuit
between the movable core and the stator core has a large effect on the
attractive force. |
Attractive Force
| Figure 2 shows the surface force density vector at the movable core. Figure
3 shows the attractive force of the solenoid valve. As shown in the graph,
the constant attractive force is obtained between 1.0mm and 2.5mm. When
the movable core moves closer to the stator core, the air gap becomes smaller,
and then the magnetic resistance changes substantially. So, when the direct
current excitation is applied, the attractive force in the moving direction
changes with the position of the movable core. |
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