Contactor

A contactor is an electrically-controlled switch used for switching an electrical power circuit.] A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24 volt coil electromagnet controlling a 240 volt motor switch.
Unlike general-purpose relays, contactors are designed to be directly connected to high-current load devices.
Relays tend to be of lower capacity and are usually designed for both normally closed and normally
open applications. Devices switching more than 15 amperes or in circuits rated more than a few kilowatts are usually called contactors. Apart from optional auxiliary low-current contacts, contactors are almost exclusively fitted with normally open (“form A”) contacts. Unlike relays, contactors are designed with features to control and suppress the arc produced when interrupting heavy motor currents.