Solenoid Valves

Solenoid valves are used for controlling the flow of liquid or gas. These are controlled units that operate electromechanically. The basic working principle of a solenoid is that when an electric current is passed, it opens or closes allowing or blocking the passage of liquid or gas. A solenoid is the electric coil, in the center of which a plunger is present. The plunger is a ferromagnetic core and is moveable. It sits at the mouth of a small opening while the valve is at rest. A strong magnetic field is created in the coil when an electric current is introduced. This exerts a force on the plunger and it moves upward leaving the orifice open.

Solenoid valves are only used for clean liquids or gases. Apart from opening or closing of outlets, they can also be used to mix or distribute media from two or more outlets. Solenoid valves are fast operating units that are commonly used in heating systems, irrigation, car washes, vacuum, compressed air, etc.

Circuit Functions of Solenoid Valves

Solenoid valves are configured as 2-way and 3-way valves and their operation is specified by their circuit function.

·        2-way Solenoid Valve:

This type of solenoid valve has two ports. One is the inlet and the other is the outlet. To ensure the smooth functioning of the valve the flow of media should be unidirectional. Usually, an arrow is marked to indicate the direction of flow. These 2-way solenoid valves are used to open and close the vent.

·        3-way Solenoid Valve:

As the name suggests, this type of solenoid valve has 3 connection ports. It has two states of placements by switching between two different circuits. A 3-way solenoid valve is used to close, open, mix, or distribute media. 

Types of Solenoid Valves

·        Normally closed

A solenoid valve that is normally closed type blocks the flow of media through it when it is de-energized. And when an electric current passes through it, an electromagnetic field is generated which pushes the plunger upward due to which the seal of the orifice opens and flow of media continues.  

·        Normally open Solenoid Valve

A solenoid valve in a normally open configuration is just the opposite. In its de-energized state, the valve is open and the media flow is allowed to pass through. And when current is passed through the solenoid, the electromagnetic field that is generated forces the plunger down as a result of which the vent is closed and flow of media is discontinued.

·        Bi-stable Solenoid Valve

A bi-stable solenoid valve can be switched on and off using a transient power supply. Once switched on or off, it stays in that position even with no power; this is why they are also called latching solenoid valves.

Bi-stable solenoid valves do not have normally closed or normally open configurations. Rather they stay in the current position when no power is provided. This latching function is achieved using permanent magnets instead of springs.

Solenoid valves are widely used in a large number of industrial and domestic applications. Irrigation systems have solenoid valves installed for automatic water supply and control. Similarly, air conditioners use solenoid valves to control air pressure. The refrigeration systems have solenoid valves incorporated to reverse the flow of refrigerants upon requirement. Water flow in dish-washers, washing machines, car washing facilities, and water tanks is also controlled through solenoid valves. They are also used in automatic locking systems for door locks.

Solenoid valves use Pulse Width Modulated (PWM) modules for varying load. The output voltage is varied according to the input voltage. Other solenoid valve accessories like a controller card and a mount bracket are also available.