Solid State Relay - SSR

What is Solid State Relay?
Solid state relay, briefly SSR, is a switching order completely composed of electronic parts. It does the same job with conventional relay and contactor. It has control circuit and power circuits like contactors and relays. It is used for switching of power circuits. There are monophase and triphase solid state relays that make switching from low currents like 1-2 amperes till high currents like 1000-2000 amperes.

How do SSR function?
In a solid state relay, when a part which is like control circuit transistor, is powered on, power circuit switches the part similar to transistor from on to off, gives energy to the system. It is an application like giving energy to coils of electrical relay or coils of contactors, thus, conversion of contacts from on to off. The difference from contactors and relays is there is a electronical circuit part instaed of  coil, and there ara electronical circuit parts instead of power contacts.