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Topic: Circuit breaker ratings (Read 761 times) previous topic - next topic


Hello All. I am working on a solar tracker using an automotive window regulator. I am using a current monitor in the system but as a last line of protection I plan on using a push-to-reset circuit breaker. I have one temporarily installed that's rated at 15A, 250vac. At a locked rotor current of 18.5 A, the circuit breaker doesn't trip. Must the breaker be rated for dc, 15A to function properly? Does it need to be rated at 12VDC? - Scotty


I think you want a DC rated breaker.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Circuit breakers generally have an inverse-time characteristic.   For fast response (<1 second) you are typically looking at an overload of 5 to 10 times rating.

Your current of 1.8 times rating will typically take around 30 to 60 seconds for the trip to effect.

The type B breaker has the fastest trip characteristic but is still generally 2 to 3 times rating.


Breakers are rated by the current they carry reliably with no chance of breaking, so a 15A
breaker will usually carry 20A indefinitely (but might eventually trip), for instance.  They are
to prevent short circuits melting the wiring, that's their main purpose, just like a fuse.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


Thanks for the replies. As it turns out, a 2A circuit breaker worked well, tripping in about a second after inducing locked rotor. - Scotty

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