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Do you know if that was overload or fault?
Very little flash if fault.
 
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Plumber (for electrons)
Industrial Electrician. EE Student
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48 Posts
Do you know if that was overload or fault?
Very little flash if fault.
I believe this is an overload situation, as the bimetallic element appears to have initiated the trip. Look at the difference between timestamps -78 ms and -76 ms and the bimetallic element (near the load terminal/right side) has changed state and the trip mechanism has begun to operate. Very interesting video for sure, and I agree that the flash size on break also seems to suggest that it was a simple overload and not a high-current fault
 

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Bilge Rat
motors and controls.........
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7,699 Posts
That's a pretty cool video!

I think that from a safety standpoint, they should show a breaker opening a fault of say, 3000 amps. Another at 8000 amps. Another of a 10KA breaker opening a fault of 20,000 amps them a 22KA model opening the same 20K amps. Finally, a 10Ka 120V breaker opening a 30,000 amp fault @480.

Of course this would be entertaining but I think it'd be beneficial for us to see what can happen if a breaker is misapplied. I think a lot of us don't take the destructive power of a high-energy system seriously.
 

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Conservitum Americum
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Discussion Starter #5

Your answers here
 

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Electrician
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Must have been a Federal Pacific one in that 1st clip as it never moved, flashed, or anything on my screen!
You can see the bar move like the video is rolling but the picture never changes.
I can see the YouTube video and everything moves, but nothing in the clip from post #1.
 

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Ready Mix concrete plant electrician
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1,974 Posts
That's a pretty cool video!

I think that from a safety standpoint, they should show a breaker opening a fault of say, 3000 amps. Another at 8000 amps. Another of a 10KA breaker opening a fault of 20,000 amps them a 22KA model opening the same 20K amps. Finally, a 10Ka 120V breaker opening a 30,000 amp fault @480.

Of course this would be entertaining but I think it'd be beneficial for us to see what can happen if a breaker is misapplied. I think a lot of us don't take the destructive power of a high-energy system seriously.
I think a good real world test would be to overload and short circuit a slash rated breaker on a high leg delta. As in the ~208 volt phase to neutral and see what happens.
In a somewhat unrelated test, @just the cowboy I haven’t forgotten about using the high leg as control voltage on a starter, I started a new job the middle of February and have been really busy. I do have a couple nice vintage NEMA Furnas starters in size 1 and 2 1/2 to try out. Maybe even a green size 0 if I look.
 

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I think a lot of us don't take the destructive power of a high-energy system seriously.
I saw an I-Line breaker blow itself apart one day. It's loud and impressive for sure.
 
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Chief Flunky
Field Service Engineer
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In an overdutied case the breaker (if it survives) often can’t open (too much magnetic force) so its not a very interesting video. Old breakers typically fail for one of four reasons. The arc chutes are so contaminated the arc keeps going and burns it up, the contact tips are so worn and pitted it either won’t close or welds shut (more common), the springs or the latching mechanism is shot mechanically and it won’t stay closed or won’t close, the grease is so dried up it either won’t open or opens so slowly it arcs and blows itself up, or the thermal or magnetic trip fails and it just never opens. This is for air breakers. OCBs can explode if you reclose too soon (hydrogen gas) or it’s full of sediment. VCBs can fail from vacuum failures but it’s generally more of a contact welding situation. SF6 gas loss causes it to arc over and fail. Out of all of these the ones where it can’t extinguish the arc correctly and quickly are the most exciting but also not all that common. Usually they fail open, fail closed (welded, corroded, trip failed), or just won’t latch, none of which make good Youtube videos.
 
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