Amperage, DC vs. AC

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Bern
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Amperage, DC vs. AC

Post by Bern » Thu Nov 16, 2006 9:17 pm

I am planning on running DC through a standard house type circuit breaker. How much will the current carrying capacity go up because of the DC over AC? There are some numbers available comparing DC to AC when working with current capacity of wires, do those same ratios work with breakers? Example, what would the trip point be for a standard 50-amp breaker?

rshayes
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Post by rshayes » Fri Nov 17, 2006 4:27 am

You want to use breakers designed and rated for DC use. A 60 Hz breaker may depend on the power waveform going to zero to quench the arc formed when the contacts open. This doesn't happen with DC power, so the interrupting capability of the breaker may be much lower on DC.

If the DC voltage is below 28 volts, you can try looking for surplus breakers intended for use in military equipment.

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MicroRem
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Post by MicroRem » Fri Nov 17, 2006 8:02 am

A good source of DC breakers is a well stocked marine supply house. In answer to your original question...hmm, I don't know....

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Crowbar
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Post by Crowbar » Sun Nov 19, 2006 1:01 pm

Amps are amps, it shouldn't affect the thermal-magnetics characteristics too much, although the DC arc is much more difficult to snuff out, therefore a DC rated breaker should be used.
Keep Prying...

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Chris Smith
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Post by Chris Smith » Sun Nov 19, 2006 7:46 pm

Not all CBs are the same any more than Amps are, stick with your required CBs.

DC and AC are ALL different for many reasons, ....temps, switching times, gaps, magnetics, and all sorts of other reasons that make the difference between AC and DC CBs.

Fuses are closer than all CBs,.... but even they are different.

Stick with what you need and are require for all of the correct reasons.

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