Thermal relays are mainly used for overload protection of motors, and are usually selected according to the type of motor, working environment, starting conditions and load properties. When the motor windings are connected, th. Thermal relays are mainly used for overload protection of motors, and are usually selected according to the type of motor, working environment, starting conditions and load properties. When the motor windings are connected, the thermal overload relay of two-phase structure can be selected. If the grid voltage is seriously unbalanced and the working. Electromagnetic relay (EMR) consists of electromagnetic system, contact system and release spring. Since the relay is used in the control circuit, the current flowing through the contact is relatively small (generally below 5A), so an arc extinguishing device is not required. Electromagnetic relay works in a way of driving the movable part in the m. The solid state relay (SSR) is a four-terminal device with two terminals as the input terminal and the other two terminals as the output terminal, and an isolation device is used in the middle to realize the electrical isolation of the input and output. Solid state relays are made of semiconductor devices instead of traditional coils, and do not ne. Signal relays are commonly used devices in automatic control systems. They are used to connect and disconnect circuits to issue control commands and reflect equipment status to form automatic control and remote control circuits. All fields of automatic control use relays. ATO signal relays are available from 1.5V ~ 24V. Signal relays play an import. The safety relay is used in the safety circuit, it's protective barrier upstream the devices in the general control system. Safety relay can be integrated with multi protection, it can even have a safety mode. For a large scale system, safety relay circuit is an important part. The common relay can be used for general overvoltage, voltage conversio.