Difference Between AC & DC Contactors

by Alex Ramirez
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motor image by Petr Efremov from Fotolia.com

Alternating current (AC) and direct current (DC) contactors are found in many industrial motors, including many automobiles. The different contactors accomplish the same thing, but they do it in different ways, starting with how they are constructed.


DC relays use a freewheel diode that discharges the electromagnetic force that gathers in the inductance when the coil is de-energized, according to Electrotechnik.net. AC contactors do not utilize the freewheel diode construction; instead they use laminating cores to prevent loss from heat and and shading coils to keep electricity running efficiently through the device.


Due to the AC's shading coils, the device can be placed in any location, as long as it has room to operate. The DC contactor needs air when operating, so the device must have plenty of gaps around it to perform properly.


While the AC contactor is considered to be a more reliable and cheaper product, the DC contactor is engineered to allow custom speed and torque. This is ideal for projects that do not follow an already existing template, such as building a robot arm from scratch.

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