AC vs. DC breakers 1

[hassankh]

I heard from a friend of mine that DC breakers have higher current interruption capability than AC ones. I wonder if we can use AC breakers, maybe with some derating, for DC application? or vice versa? I have seen many MCBs and MCCBs that are used for both DC and AC application. Even their nameplate indicates that.
Thanks in advance

 

[Skogsgurra]

A typical derating of a 10A 250V AC breaker for use in an inductive DC Circuit could be 3A 30V.
So, I would be very hesitant to use an AC breaker in a DC Circuit.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[dpc]

Agree with Gunnar. In the US, it would be a code violation to apply a breaker in a dc system if it did not have a dc rating listed on the device by the manufacturer.

 

[DanEE]

"friend of mine that DC breakers have higher current interruption capability than AC ones"

Ever think about why this might be necessary? An AC voltage has two zero crossings per cycle, and contributes a bit toward getting the arc plasma that happens when the breaker opens to extinguish. Notice those little screened vents on some of the larger breakers? that's so the arc plasma can which is a mighty fine conductor can escape the breaker.

Now with DC steady state voltage, the arc is a bit more difficult to suppress.. needs more contact spacing distance, faster switching and other changes to the design. If the arc doesn't extinguish, the breaker begins to look a bit more like an arc welder with all its smoke and glory and 10,000 degree heat.. Interpret as electrical fire..

Not something I would take a chance on..