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What's the difference between AC contactor and DC contactor?

Dec 25, 2018

What's the difference between AC contactor and DC contactor?  Why can't exchange?

1.The difference

1)The iron core of AC contactor is different: the iron core of AC contactor is made of silicon steel sheets which are insulated from each other and is double E-shaped. The core of DC contactor is mostly made of whole soft iron, mostly U-shaped.

2)The arc extinguishing system is different: AC contactor adopts stripping arc extinguishing, DC contactor adopts magnetic blowing arc extinguishing device.

3) Coil turns are different: The coil turns of AC contactor are few, and it is connected to AC. The ac contactor breaks the ac circuit. The dc contactor breaks the direct current circuit. The operation frequency of ac contactor is 600 times/hour, with low cost of use, while the operation frequency of dc contactor can be up to 2000 times/hour, with high cost of use.

2.Ac contactor cannot be used as dc contactor for the following reasons:

1.The ac contactor can replace the dc contactor in case of emergency, and the suction time shall not exceed 2 hours (Because ac coils dissipate less heat than dc coils, this is due to their different structures), If you really want to use it for a long time, you need to put a resistance in the ac coil, whereas dc cannot replace ac contactor.

2.The number of coil turns of ac contactor is less and that of dc contactor is more, can distinguish by the volume of the coil. For the case that the main circuit current is large (Ie>250A), The contactor adopts the coil of dc relay with double winding in series with high resistance and low current. If the ac connection is not damaged,sometimes open and sometimes close,but the coil reactance of ac relay is small, the current is large, if connected to the dc current will damage the coil.

3.The coil turns of the ac contactor are small and the resistance is small. When the coil is connected to the ac current, a large inductive resistance will be generated, this inductance is much greater than the resistance of the coil, and the excitation current of the coil mainly depends on the magnitude of the inductance. If the direct current is passed through, the coil will become a pure resistance load. At this time, the current flowing through the coil will be very large, making the coil hot or even burnt out.