AFCI Breakers

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kwired said:
I really have no idea but am going to guess when welding steel you can get away with using AC current because of the carbon in the steel, and maybe other reasons on top of that.
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I would not consider welding a 'self sustaining arc' welding has a human or a computer working to maintain that arc.

If I drop a welding lead onto grounded steel it is not just going to keep arcing.
 
iwire said:
I would not consider welding a 'self sustaining arc' welding has a human or a computer working to maintain that arc.

If I drop a welding lead onto grounded steel it is not just going to keep arcing.
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Considering the electrode doesn’t touch the base metal except for striking the arc I’d say it’s a continuous arc. If you allow the electrode to move gradually away or just let it burn away you can watch the arc propagation. Depending on the current the arc can extend a fair way until it extinguishes
 
iwire said:
I would not consider welding a 'self sustaining arc' welding has a human or a computer working to maintain that arc.

If I drop a welding lead onto grounded steel it is not just going to keep arcing.
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Tony S said:
Considering the electrode doesn’t touch the base metal except for striking the arc I’d say it’s a continuous arc. If you allow the electrode to move gradually away or just let it burn away you can watch the arc propagation. Depending on the current the arc can extend a fair way until it extinguishes
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iwire said:
Continuos? Sure it can be.

Self sustaining? Nope.
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Good points here, with the welder the operator is going to continue to feed material,move the torch tip, etc. to maintain the gap between arc electrodes, in a circuit in premises wiring should an arc develop, it will consume material and widen the gap between electrodes - at some point (on a timeline with milliseconds in the measurement range) that gap grows enough that the applied voltage can no longer maintain the arc.
 
Tony S said:
A blunt question, can you weld?
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Oxy / gas, stick (arc), MIG and played around doing TIG.

Spent many hours fabricating metsl.

Not one of the welding methods I have done is self sustaining, all require the feeding of new material into the arc by another force.
 
Even if the intent behind AFCIs is to catch brief sparks, it still doesn't change anything. IF anything its worse because brief arcs are part of every load.
 
mbrooke said:
Even if the intent behind AFCIs is to catch brief sparks, it still doesn't change anything. IF anything its worse because brief arcs are part of every load.
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As I understand it the AFCI has to see the arc signature for 4 out of 8 half cycles and the current has to be at least 5 amps for a series arc and 75 amps for a parallel arc.
 
don_resqcapt19 said:
As I understand it the AFCI has to see the arc signature for 4 out of 8 half cycles and the current has to be at least 5 amps for a series arc and 75 amps for a parallel arc.
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Ok, that clears it up a bit. So its the 5 amps series that is causing most nuisance tripping?
 
Some arc welding units ride a high frequency (RF) voltage on top of the main arc voltage to provide continuous excitation of the arc during the zero crossings of the 60/50 Hz supply current.
 
mbrooke said:
I agree, this in reality is a parallel fault. To me a series fault would be where only one side of the zip conductor is cut and the two are making contact.
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The tests do include a test with a series load. But I question that the series event created in the lab means much in the field.
 
mbrooke said:
I agree, this in reality is a parallel fault. To me a series fault would be where only one side of the zip conductor is cut and the two are making contact.
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I don't understand this point of view. Once you cut a conductor in the zip cord, and bring two such conductors together close enough to arc, what does it matter where the conductors were in the zip cord before you cut it?

It seems to me that a series arc is one where the arc path is in series with the load, and a parallel arc is one where the arc path is in parallel to the load. The test described is clearly an arc path in series with the load.

Cheers, Wayne
 
It seems to me that a series arc is one where the arc path is in series with the load, and a parallel arc is one where the arc path is in parallel to the load. The test described is clearly an arc path in series with the load.

Cheers, Wayne
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Exactly...
 
wwhitney said:
I don't understand this point of view. Once you cut a conductor in the zip cord, and bring two such conductors together close enough to arc, what does it matter where the conductors were in the zip cord before you cut it?

It seems to me that a series arc is one where the arc path is in series with the load, and a parallel arc is one where the arc path is in parallel to the load. The test described is clearly an arc path in series with the load.

Cheers, Wayne
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But in the UL test preparation of the zip is not a series cut, rather both the neutral and line conductors have the insulation removed. Yes these two parallel cuts are applied in series with a load, but in the real world the arc current would not be limited by the load rather by the available fault current at the outlet. Thus a plug top fuse would mitigate the issue.
 
mbrooke said:
But in the UL test preparation of the zip is not a series cut, rather both the neutral and line conductors have the insulation removed. Yes these two parallel cuts are applied in series with a load, but in the real world the arc current would not be limited by the load rather by the available fault current at the outlet. Thus a plug top fuse would mitigate the issue.
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But we can sell AFCI's for $40-60 and someday we may get them to do everything we want, those plug top fuses may only be a quarter to a dollar;)
 
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