A contactor is an electrically controlled switch used for switching an electrical power circuit, similar to a relay except with higher current ratings. A contactor is controlled by a circuit which has a much lower power level than the switched circuit. NEMA contactors are often used in facility applications where flexibility in varying amperage or horsepower is needed without having to replace the unit. These heavy duty devices are available in open frame as well as a variety of enclosures from NEMA 1 to NEMA 7 and 9 for hazardous locations.