I was sent this faulty Wylex circuit breaker to take a look at. It's a common brand used in consumer units (home distribution boards) in the UK. The contacts had suffered burn damage and were not making a reliable connection. After seeing what was wrong I thought it would be good to show how the mechanism in an MCB (Miniature Circuit Breaker) works. Especially the bit that lets it still trip while the toggle is being held in the on position.
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If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
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I know where to look for little fins to cool things off with . 😉 Thanks again Clive .
I was told by the speaker at the International Arc Flash conference that the arc always travels away from the energy source irrespective of position of the electrodes.
Clive, one little remark. The short circuit current rating is 6000 amps in a rectangle. That means in home application 6000 amps and 10000 amps industrial. It means also that you can try to switch on the breaker whiteout destroying while there is stil a secondary problem. (for example a short circuit).
Tres interesting, and a lot more complex than I might have thought. Somewhere hereabouts, we have one that will not switch back on. It tripped one day for no obvious reason, and the dolly will no longer reset nor latch into the on position – I wonder where it got put, and if it could be repaired, though by the sound of it, it's not worth repairing even if it were physically possible.
Would the magnetism from the solenoid or its components work to break up the arc?
I probably won't get a answer but if I use a circuit breaker with a higher amp than the device I'm using, would it only trip when it goes above that amperage?
Interesting stuff, any chance you could do an RCD also, I'd be mega curious to see inside on of those but don't have a spare knocking around or the BigCliveDotCom wisdom to understand wtf its doing, but I am sure it would also be some well engineered and interesting electromechanical goodness.Maybe if someone has an old non functional / spare RCD they'd like to donate it to the cause?
you know if I had a breaker I would honestly want it to vent out in the front so I could see if it was smoking and burning up
Cool thanks for this, always wondered how a MCB worked inside, what causes it to trip etc. Great video as always 🙂
Good advice as usual.interesting stuff
It does seem weird that the arch would want to move away from where the contacts are close. Perhaps the hot expanding gases carry the arch that way because its the only opening to atmosphere and the only direction to expand to.
I guess 6000 amps sounds like a lot until you look at an ampere graph for a dead short. I wonder how they (if at all?) standardize arc ratings?
Couldn't the solenoid blow the arc?
awesome
A broken circuit breaker?
Interesting, our US circuit breakers seem much simpler and more rudimentary, but same idea, thermal strip and the solenoid. Maddeningly unstandardized, different panels take different styles, Eaton, Square D, Siemens Cutler Hammer…..