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What is a solenoid?

Solenoid is the generic term for a coil of wire used as an electromagnet. It also refers to any device that converts electrical energy to mechanical energy using a solenoid. The device creates a magnetic field from electric current and uses the magnetic field to create linear motion. Common applications of solenoids are to power a switch, like the starter in an automobile, or a valve, such as in a sprinkler system.

How a Solenoid Works

A solenoid is a coil of wire in a corkscrew shape wrapped around a piston, often made of iron. As in all electromagnets, a magnetic field is created when an electric current passes through the wire. Electromagnets have an advantage over permanent magnets in that they can be switched on and off by the application or removal of the electric current, which is what makes them useful as switches and valves and allows them to be entirely automated.

Like all magnets, the magnetic field of an activated solenoid has positive and negative poles that will attract or repel material sensitive to magnets. In a solenoid, the electromagnetic field causes the piston to either move backward or forward, which is how motion is created by a solenoid coil.

How Does a Solenoid Valve Work?

In a direct-acting valve, electric current activates the solenoid, which in turn pulls a piston or plunger that would otherwise block air or fluid from flowing. In some solenoid valves, the electromagnetic field does not act directly to open the conduit. In pilot-operated valves, a solenoid moves the plunger, which creates a small opening, and pressure through the opening is what operates the valve seal. In both types, solenoid valves require a constant flow of electrical current to remain open because once the current is stopped, the electromagnetic field disperses and the valve returns to its original closed position.

Electric Solenoids

In an automobile ignition system, the starter solenoid acts as a relay, bringing metal contacts into place to close a circuit. The starter solenoid receives a small electric current when the car’s ignition is activated, usually by the turn of the key. The magnetic field of the solenoid then pulls on the contacts, closing the circuit between the car’s battery and the starter motor. The starter solenoid requires a constant flow of electricity in order to maintain the circuit, but because the engine is self-powering once started, the solenoid is inactive for most of the time.

Uses for Solenoids

Solenoids are incredibly versatile and extremely useful. They’re found in everything from automated factory equipment to paintball guns and even doorbells. In a chime doorbell, the audible chime is produced when a metal piston strikes a tone bar. The force that moves the piston is the magnetic field of a solenoid that receives electric current when the doorbell is pushed.

Solenoid valve is an automatic basic element used to control the direction of fluid, belonging to actuator; It is usually used in mechanical control and industry
Above the valve, the medium direction is controlled, so as to control the valve switch.

Solenoid valves are divided into three categories in principle:

1) direct acting solenoid valve:

Principle: when energized, the solenoid coil generates electromagnetic force to lift the closing part from the valve seat and open the valve; when powered off, the electromagnetic force disappears, the spring presses the closing part on the valve seat and the valve closes.

Features: it can work normally under vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.

2) distribution solenoid valve Direct acting solenoid valve:

Principle: it is a combination of direct acting and pilot type. When there is no pressure difference between the inlet and outlet, the solenoid force will directly lift the small pilot valve and the closing parts of the main valve upward and open the valve. When the inlet and outlet reach the starting pressure difference, the solenoid force will pilot the small valve, the pressure in the lower chamber of the main valve will rise and the pressure in the upper chamber will fall, so as to facilitate the opening of the valve Push the main valve upward with differential pressure; when power is off, the pilot valve uses spring force or medium pressure to push the closing part and move downward to close the valve.

Features: it can also act when there is zero differential pressure or vacuum and high pressure, but the power is large, so it must be installed horizontally.

3) pilot solenoid valve:

Principle: when power is on, the solenoid force opens the pilot hole and the pressure in the upper chamber drops rapidly, The pressure difference between the lower part and the higher part is formed around the closing part, the fluid pressure pushes the closing part to move upward, and the valve opens; in case of power failure, the spring force closes the pilot hole, the inlet pressure quickly forms the pressure difference between the lower part and the upper part around the valve closing part through the bypass hole, and the fluid pressure pushes the closing part to move downward to close the valve.

Features: the upper limit of the fluid pressure range is high, which can be installed arbitrarily (to be customized) but the fluid differential pressure condition must be met.

Post time: Sep-25-2021