What is the solid state relay, what are the advantages and disadvantages?

Solid-state relay (also known as solid relay) English name is Solid State Relay, referred to as SSR. It is a non-contact switching device with relay characteristics that uses semiconductor devices instead of traditional electrical contacts as switching devices. Single-phase SSR is a four-terminal active device, in which two input control terminals, two output terminals, and the input and output are light Isolated, the input terminal can be switched from off-state to on-state after adding DC or pulse signal to a certain current value.

Solid state relays work reliably, long life, no noise, no spark, no electromagnetic interference, fast switching speed, strong anti-interference ability, and small size, impact resistance, vibration resistance, explosion-proof, moisture-proof, anti-corrosion, and TTL, DTL, Logic circuits such as HTL are compatible with direct driving of large current loads with tiny control signals. The main disadvantages are the on-state voltage drop (required corresponding heat dissipation measures), off-state leakage current, AC and DC cannot be universal, the number of contact groups is small, and other indicators such as over-current, over-voltage and voltage increase rate, current rise rate are poor.