Electromagnetic relay is an electronic control device. It has a control system (also called input loop) and a controlled system (also called output loop). It is usually used in automatic control circuits. It actually uses a lower current and lower current. A type of "automatic switch" that controls a larger current and a higher voltage. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit.
The basic structure and working principle of the electromagnetic relay are similar to the contactor, which is composed of iron core, armature, coil, return spring and contact. Because the electromagnetic relay is used for the auxiliary circuit, its on and off current is small, so it is not equipped with an arc extinguishing device. The electromagnetic system of the electromagnetic relay has two types of direct-acting type and snap-in type. The electromagnetic mechanism of the AC relay has U-shaped snap-in type and E-shaped direct-acting type.
Electromagnetic relays are divided into DC relays and AC relays according to the types of electromagnetic coil currents. Electromagnetic relays are divided into current relays and voltage relays, and intermediate relays according to the way coils are connected in the circuit. DC relays and AC relays can be divided into current relays, voltage relays and intermediate relays according to their connection in the circuit.