Solenoid basic working principle and a practical Solenoid valve

A solenoid is a simple electromagnetic device that converts electrical energy directly into linear mechanical motion, but it has a very short stroke (length of movement), which limits its applications.

Basic working principle of solenoid

The solenoid consists of a coil of wire with an iron plunger that is allowed to move through the center of the coil. Above figure shows the solenoid in the un-energized state.

                                               Fig: Basic working principle of solenoid

  

Notice that the plunger is being held about halfway out of the coil by a spring. When the coil is energized, the resulting magnetic field pulls the plunger to the middle of the coil. The magnetic force is unidirectional — a spring is required to return the plunger to its un energized position.

Working principle of a practical Solenoid valve

A solenoid valve is the combination of a basic solenoid and mechanical valve. So a solenoid valve has two parts namely- Electrical solenoid, mechanical valve.

Solenoid converts electrical energy to mechanical energy and this energy is used to operate a mechanical valve that is to open, close or to adjust in a position.

Image of – Working procedure of a typical Solenoid valve:

                                            Fig: A typical Solenoid valve working principle

Limitation of Solenoid valve

The main limitation of the solenoid is its short stroke, which is usually under an inch. Still, there are many applications for short-stroke linear motion; examples are activating electric car-door locks, opening and closing valves, and triggering mechanical latches.

Most applications use the solenoid as a on or off device—that is, the coil is either completely energized or switched off. However, variable-position control is possible by varying the input voltage.