What is the difference between tripping mechanism of DC MCCB and AC MCCB?

MCCB designed for interrupting an AC load do not require the contacts to separate as fast as for a DC load since AC goes through a zero crossing every half cycle. The arc will be extinguished each time the voltage goes through a zero crossing, provided the load is not highly inductive. The contacts only have to get far enough apart to prevent re-flash. Not so with interrupting a DC load. Not only do the contacts have to separate quickly, there also has to be a means of quenching (cooling) the arc to extinguish it since there is no zero crossing in DC Loads.

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