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A solenoid is a simple linear actuator that uses a principle of position-dependent reluctance to

convert electrical energy into a mechanical energy of the plunger movement which is then used to apply force. The cross-sectional view of a typical solenoid is shown in Figure 1.

Linear Solenoids

Figure 1: Cross-section of a solenoid. Dashed lines show magnetic flux.

The magnetic path encountered by the flux consists of the outer shell, the plunger, and the

front and back air-gaps. Because the back air-gap is determined by the plunger position,

the overall effective reluctance is position-dependent. Therefore, the total flux flowing through

the magnetic circuit depends on the applied magneto-motive force mmf (ampere-turn product)

as well as the position of the plunger.

Figure 2: SLU Solenoid Aisin Warner 55/50

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