Relay is a kind of electrical appliance that makes a predetermined step change of the controlled quantity in the electrical output circuit when the change of the input quantity (e.g. current, voltage, etc.) reaches the specified requirements. Its working principle is mainly based on electromagnetic induction or thermal effect. In electromagnetic relays, when the coil is energized, a magnetic field is generated, which in turn attracts the contacts to close, realizing the energization of the circuit; and when the coil is de-energized, the magnetic field disappears, the contacts are disconnected, and the circuit is also disconnected. Thermal relay is through the heat generated by the current to make the bimetal deformation, when the deformation reaches a certain level, to promote the linkage action, so that the control circuit is disconnected, so as to realize the function of the protection circuit.

Relays are widely used in a variety of automation equipment, such as home appliance control, automotive electronics, industrial automation, communication equipment and so on. In household appliances such as refrigerators and washing machines, relays are used to control the starting and stopping of motors; in vehicles, relays are used to control the operation of lights, windshield wipers, air-conditioning systems and other components; in production lines, relays are used to control the action of motors, valves and other actuators; and in communication equipment, relays are used for signal transmission and switching.

Main functions

1. Expanding the control range: multi-contact relays can switch, open and close multiple circuits at the same time according to different forms of control signals.

2. Amplification: sensitive relays, intermediate relays, etc. can be used to control high-power circuits with a small amount of control.

3. Comprehensive signal: multiple control signals can be input into the multi-winding relay according to the specified form, and achieve the predetermined control effect after comparison and synthesis.

4. Automatic, remote control, monitoring: relays can be used with other electrical appliances to form a programmed control line to realize automatic operation, remote control and monitoring functions.