Relays are usually used in automatic control circuits. They are actually “automatic switches” that use a small current to control a large current operation. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit.

Relays generally have an induction mechanism (input part) that reflects certain input variables (such as current, voltage, power, impedance, temperature, pressure, speed, light, etc.); It has an actuator (output part) that can control the “on” and “off” of the controlled circuit; In the input and output parts of the relay, there is an intermediate mechanism for coupling and isolation of the input, functional processing and driving of the output part (the driving part).

In terms of its role in the controlled circuit, the relay is equivalent to a “switch”, but it is not operated by people, but a kind of automatic remote control element.

The basic working principle of the relay

Relays are generally composed of iron core, coil, armature, contact reed, etc. When the power is switched on, the electromagnetic effect will be generated, and the electromagnetic force will attract the armature and make it contact with the iron core, which will drive the normally closed electric contact of the armature and the normally open contact to attract. After the current is cut off, the electromagnetic suction will be gone, and the armature will return to its original position and cut off the circuit.

The transfer contacts of the relay are one moving contact and two static contacts of the relay. Among them, the moving contact and the static contact 1 are in a closed state, which is called the normally closed contact; the moving contact and the static contact 2 are in a disconnected state, which is called the normally open contact.

When the coil is energized, its moving contact and static contact 1 immediately disconnect and close with static contact 2, cut off the control circuit of static contact 1, and contact the control circuit of static contact 2.

When the coil loses power, the moving contact is reset, that is, the moving contact is reset and disconnected from the static contact 2 and is reset and closed with the static contact 1. The control circuit of the static contact 2 is cut off and the control circuit of the static contact 1 is connected.

The main function of the relay

Expand the control range: for example, when the control signal of a multi-contact relay reaches a certain value, the multi-circuit can be switched on, off and connected at the same time according to different forms of contact groups.

Amplification: for example, sensitive relays, intermediate relays, etc., can control a large power circuit with a very small amount of control.

Integrated signal: for example, when multiple control signals are input into the multi-winding relay in the prescribed form, the predetermined control effect can be achieved through comparison and integration.

Automatic, remote control, monitoring: for example, relays on an automatic device, together with other electrical appliances, can form a programmed control circuit for automatic operation.