Three phase solid state relays

The main differences between Solid State Relays (SSR) and Electromechanical Relays (EMR) lie in their structure and performance. SSRs have no mechanical contacts and use semiconductor devices for switching, offering longer lifespan, faster switching speeds, and noiseless operation, making them suitable for high-frequency operations and harsh environments. EMRs rely on electromagnetic coils to drive mechanical contacts, resulting in slower switching speeds, shorter lifespan, and noise during operation, and they are more sensitive to vibration and shock. SSRs consume less power and are ideal for applications requiring frequent switching, such as heating and motor control, while EMRs are suitable for general switching applications, especially where electrical isolation is needed.

A margin should be left when selecting the voltage and current of the solid state relay. For resistive load: the current is selected according to 2.5~4 times the load current, and the voltage is selected according to 2~2.5 times the load power. Inductive load: current is selected according to 3-7 times load current, voltage is selected according to 2.5-3 times load voltage.

The main differences between a Silicon Controlled Rectifier (SCR) module and a Solid State Relay (SSR) lie in their functions and composition. An SCR can regulate current by controlling the conduction angle, while an SSR primarily acts as a switch and cannot regulate current. A Solid State Relay consists of an SCR and a synchronous trigger drive, with an integrated isolation trigger terminal, whereas an SCR requires external isolation. Although they may have similar functions in some applications, they differ significantly in regulation capability and internal structure.

Thyristor modules require a dedicated trigger circuit to provide precise trigger pulses, suitable for applications needing precise control. Solid-state relays are triggered via optocouplers, featuring built-in electrical isolation, and are easy to install, making them suitable for applications with lower switching frequencies. The anti-interference capability of thyristor modules depends on the design of the trigger circuit, while solid-state relays have relatively strong anti-interference due to optocoupler isolation, though electromagnetic interference should still be considered.