The five common relays are as follows:
Thermal relay, undervoltage relay, time relay, speed relay, intermediate relay.
There are many types of relays, and different application scenarios require different types of relays. Here are several classification methods of relays. Relays are classified according to their uses, or they are classified according to their action time. The models of relays are different.
According to the working principle, the relays are classified into electromagnetic relays, inductive relays, thermal relays, mechanical relays, electric relays and electronic relays.

The relay is mainly used for the protection and control of low-voltage electrical equipment, and is used for information transmission such as judgment and logical operation. It is an automatic switching element with isolation function, and has a control system and a controlled system. The role of regulation and safety protection. As a control element, the relay has the functions of expanding the control range, amplifying, integrating signals, automatic, remote control and monitoring.