As far as I have noticed, "contactor" term is used for large electromechanical-switches handling large current while a "relay" is low current handling electromechanical-switch.
And here is the definition from AIEE (todays IEEE) Relay: A device by which contacts in one circuit are operated by a change in conditions in the same circuit or in one or more associated circuits.
Contactor: A device for repeatedly establishing and interrupting an electric power circuit.
In the semiconductor testing industry, contactor also refers to pogo pin based fixtures used to establish electrical connection between the IC (Device Under Test) and Test Board (Performance Board, Family Board, DUT Board, etc) . I hope this is not the "contactor" that you are referring to. Just some clarification, thanks...
desperado1,
They are basically the same thing. The term "Contactor" is often used for electromechanical witches that control large motor loads.
Regards,
Kral
Just as other buddies mentioned relay is normally used when currents of max 6 amp are used but with contactors above this, hundreds of amps. When the electricity of one store,ie, is turned off we apply a small signal to activate the contactor,a large box.
For example in a tv set w have a relay to activate the tv or the degaussing circuit, it is a small box.
rgds
marco