The electromagnetic relay is a relay that drives the movable part of the magnetic circuit by the electromagnetic attraction generated by the control current through the coil to realize the contact opening, closing or conversion function. Simply put, it is a switch that uses weak electricity to control strong electricity. It has a control system (also called an input loop) and a controlled system (also called an output loop), and is usually used in automatic control circuits. The following introduces some basic knowledge of electromagnetic relays:
1. Structure
Electromagnetic relays are generally composed of magnetic circuit system, contact system and return mechanism.
(1) Electromagnetic system: an induction mechanism, a magnetic circuit system composed of an iron core made of soft magnetic materials, a yoke and an armature, and a coil assembly. It is magnetic when it is energized, and it can be regarded as the core part of the electromagnetic relay;
(2) Contact system: the actuator, which is assembled by different forms of contact reeds or contact pieces used as contacts in a certain insulating manner. That is, the part that determines which circuit is energized;
(3) Transmission and restoration mechanism: the intermediate comparison mechanism. The transmission mechanism that realizes the action of the relay refers to the mechanism that transmits the armature movement to the contact reed when the coil is excited. Generally, the contact reed connected with the armature is directly driven or indirectly driven by the movement of the armature.
working principle
As long as a certain voltage is applied to the two ends of the coil, a certain current will flow through the coil, which will produce electromagnetic effects. Under the action of electromagnetic force, the armature will overcome the pulling force of the return spring and attract to the core, thereby driving the armature. The moving contact and the static contact (normally open contact) are pulled together. When the coil is de-energized, the electromagnetic attraction will disappear, and the armature will return to its original position under the reaction force of the spring, releasing the moving contact and the original static contact (normally closed contact). This pulls in and releases, so as to achieve the purpose of conducting and cutting off in the circuit.