Question { Siemens, 15309 }

what is the difference between relay and a contactor.

Answer

All magnetic contactors are a type of relay, but relays can
be significantly more complicated than contactors.

The contactors is primarily used for switching larger power
circuits (such as motors, for example), since the control
logic components cannot meet the current & voltage duty of
the power circuit.

Relays can be as simple as 12 V dc solenoids with 12 V, 0.5
A rated contacts. Or they can be as complicated as
microprocessor-based devices used to detect disturbances
(faults) on the power system and signal a local or remote
switching device (breaker) to trip the circuit.