What is an electromagnetic relay

At the heart of modern electrical engineering are twoThe main element of most circuits is a semiconductor transistor and an electromagnetic relay. If we mentally remove these two inventions, it is difficult to imagine how the future history of mankind would develop.

Perhaps there would have been evolved aroundthe middle ages, but, on the contrary, progress would go along the path of managed development of biological systems. But let's leave these reflections to the science fiction writers. One thing is clear: the electromagnetic relay for all electrical engineering is the same as the internal combustion engine for modern transport. That is - an indispensable component.

How is the electromagnetic relay arranged?

The design of this circuit element is very simple. This is the reason for its high reliability: in some plants, the year 1940 relay is still in operation.

Before describing the construction, it is necessaryremember one of the laws of physics - electromagnetism. It is known that around any material along which an electric current passes, there is a special kind of matter - a magnetic field. Its strength (potential) depends on two parameters: the magnitude of the current flowing and the length of the conductor.

It is obvious: if each unit of length generates a field, then the conductor is longer, the more pronounced the magnetic effect. This means that if a metal object is placed next to such a conductor, then it will be influenced by the forces of attraction. If their value is sufficient, then the object will move from its place. Obviously, the other thing: increasing the field intensity by increasing the length of the conductor is not very convenient - the device should be compact, and the total field vector should be concentrated at one point, rather than being sprayed along the entire conductive material. The increase in current is also irrational, as this causes excessive heating and non-optimal use of materials. However, there is a solution.

It consists in applying not a straight wire, but a coil with a core. This allows you to use kilometers of thin wire on a small volume.

The electromagnetic relay is just insidesuch a coil. The second part of the design is a metal plate of a special shape, which has one degree of freedom. That is, when a magnetic field arises, the plate is attracted to the end side of the coil. With the disappearance of the current, the effect stops, and the return spring throws the plate back to its original position.

On the attracting bar are fixed jumpers -group of moving contacts. The second part (rigidly fixed) is near. When the plate is shifted, the contacts close. If they are included in the circuit break, then, by controlling the operation of the coil, it is possible to commute the connected circuits. That's how the electromagnetic relay works. By the way, depending on the method of location of fixed contacts, they can be normally closed (open when a magnetic field appears) and normally open (collect the circuit).

The electromagnetic AC relay in the structure contains a special turn of the conductor, the field of which prevents rattling due to the frequency nature of this current.