A contactor is another name for relay, usually used for large high power relays for starting motors. A small signal like 24V can control the relay coils to close the main contacts that carry tens or even hundreds of amps and 240 VAC. ATO contactors are divided into AC Contactors (voltage AC) and DC Contactors (DC voltage), they applies to electricity, electricity distribution and electricity. Contactor broadly refers to the use of industrial electricity flow through the coil current to produce magnetic field, close the contacts to achieve control of electrical load.