What is Solenoid?
The solenoid is the coil of the insulated or the enameled wire wound around the solid or hollow shape made up of iron or steel or any other ferromagnetic material. The material around which the coil is wound is called as the core material. When current is passed through the coil of wire it exhibits the properties of electromagnetism and the magnetic flux or magnetic field is inducted within the core material as well as around the coil. Thus any other material kept around the solenoid through which the electric current is passing experiences magnetism.
If the core is hollow, the magnetic field is generated inside the empty space and in case of the solid core the magnetic field is generated around the core and coil. Thus when the current is passing though the solenoid coil, it acts as the electromagnet and when the current is removed it loses the property of electromagnet.
What is Solenoid Valve?
The solenoid valves are used to control the flow of the liquid or the gas (called as fluids) in the pipeline or in certain process. The solenoid valve is the electromechanical valve comprising of the solenoid coil and a plunger which is connected to the stem of the valve. In solenoid valves the core around which the insulated coil is wound is hollow. In this hollow portion there is round shaft like plunger or piston that can move up and down inside the hollow space. The plunger is connected to the spring that keeps it in place and controls its motion (refer the figure below for various parts of the solenoid valve).
When the current is passed through the coil, it gets energized and the magnetic flux is developed around the coil, which allows the motion of the plunger. When the current is removed from the coil, it gets de-energized and the magnetic flux is also removed. The plunger can move to the extremes from top to down and vice versa or it can move in small increments as per the current passing through the coil.
The ordinary valves used for the control of the flow of the fluid comprise of the handle connected to the stem of the valve. The stem of the valve is connected to the disc that controls the amount of opening of the valve called orifice. When the handle of the valve is rotated manually the stem of the valve and also the disc moves up or down which allows the opening of the valve.
In case of the solenoid valves the typical parts of the valve, like its body, the disc and the stem are available but there is no handle of the valve. The stem of the valve is connected to the plunger of the solenoid valve. When the current passes though the coil, the plunger moves inside the hollow spaces, causing the motion of the stem of the valve and controlling the opening of the orifice.
The various parts of the solenoid valve are shown in the figure below. Also shown is one of the commonly used solenoid valve available easily in the market.
Book: Electric Controls for Refrigeration and Air Conditioning by B. C. Langley, Printice-Hall, Inc
This post is part of the series: What are Solenoid Valves? How Solenoid Valves Work?
This is the series of articles that describes what the solenoid valve is, the principle of working of the solenoid valve, various parts of the valve, how the solenoid valve works and the applications of the solenoid valves.