Dc Contactor.

[chris1373]

Most contactors have a table for AC3. How can i know how much DC power can they handle? In example a contactor for 100kw in 400V.

 

Thanks for any answer.

Chris.

[mariomaggi]

chris1373,

there is no a fix ratio between AC perfomances and DC performances.

AC ratings for a certain contactor are always better that DC ratings.

 

In some cases the differences are big, in other cases differences are not so big.

 

You have to ask the contactor manufacturer, specifying the type of load (inductive, resistive, etc.)

 

Regards

Mario

[chris1373]

Thanks for your answer Mario.

 

Chris.

[marke]

Hello Chris

 

The limitation is the ability for the contacts to extinguish an arc when the contactor opens.

In the case of AC current, the current must go through zero at twice the line frequency and this will help to extinguish any arc that remains.

With DC, there is no zero current and so the arc can continue for a long period unless there is some arc extinguishing features of the contactor. This is why there is a very large difference between contactors and their DC ratings.

 

Best regards,