A typical electric solenoid actuator consists of a coil, armature, spring, and stem. This is illustrated in the figure below:
The coil is connected to an external current supply. The spring rests on the armature to force it downward. The armature moves vertically inside the coil and transmits its motion through the stem to the valve.
When current flows through the coil, a magnetic field forms around the coil. The magnetic field attracts the armature toward the center of the coil. As the armature moves upward, the spring collapses and the valve opens. When the circuit is opened and current stops flowing to the coil, the magnetic field collapses. This allows the spring to expand and shut the valve.
Related: Pneumatic Actuators
The key advantage of solenoid actuator is their quick operation. Additionally, they are much easier to install than pneumatic or hydraulic actuators. In of this, solenoid actuators have two disadvantages; first they have only two positions: fully open and fully closed. Second, they don’t produce much force, so they typically operate relatively small valves.
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