What is the relay?
Relay is an electrical control device. It has the interactive relationship between the control system (also known as input loop) and the controlled system (also known as output loop). Usually used in automatic control circuits, it is actually an 'automatic switch' that uses small current to control high current operation. Therefore, it plays an important role in the circuit such as automatic regulation, safety protection and conversion circuit.
Its working principle is to use the interactive relationship between the control system and the controlled system of the relay. When the input reaches the specified value, the relay turns on or off the controlled output circuit, so as to achieve the function of control. The input quantity here can be divided into electrical quantity (such as current, voltage, frequency, power, etc.) and non electrical quantity (such as temperature, pressure, speed, etc.).
Function of relay
According to the action principle, the relay can be divided into:
1. Solid state relay:
A relay whose input and output functions are completed by electronic components without mechanical moving parts.
2. Electromagnetic relay:
A relay that generates a predetermined response from the relative movement of the mechanical components under the action of the current in the input circuit. It includes DC electromagnetic relay, AC electromagnetic relay, magnetic holding relay, polarization relay, tongue spring relay and energy-saving power relay.
3. Time relay:
When the input signal is added or removed, the output part needs to delay or limit the time to close or disconnect the relay of its controlled line within the specified time.
4. Acceleration relay:
When the acceleration of the moving object reaches the specified value, the controlled circuit will be turned on or off.
5. Wind speed relay:
When the wind speed reaches a certain value, the controlled circuit will be turned on or off.
6. Temperature relay:
A relay that operates when the external temperature reaches the specified value.
7. Other types of relays:
Such as optical relay, acoustic relay, thermal relay, etc.
The relay has the advantages of fast action, stable operation, long service life and small volume. It is widely used in power protection, automation, motion, remote control, measurement and communication devices.
As a control element, the relay has the following functions:
1. Expand the scope of control.
For example, when the control signal of multi contact relay reaches a certain value, it can change, disconnect and connect multiple circuits at the same time according to different forms of contact groups.
2. Control the big with the small.
Such as: sensitive relay, intermediate relay, etc. with a very small control quantity, you can control a high-power circuit.
3. Integrated signal.
For example, when multiple control signals are input into the multi winding relay in the specified form, the predetermined control effect can be achieved through comparison and synthesis.
4. Automatic, remote control and monitoring.
For example, the relay on the automatic device and other electrical appliances can form a program control circuit to realize automatic operation.