VFDs & PLC in same enclosure?

One question I have is where is the arc flash potential coming from? Is it the drive itself? There are a lot of drives that are available in NEMA4/12/etc. These are typically placed outside of an enclosure on the wall or unistrut. The NEMA ratings does not change the arc flash potential correct? So you would think that a NEMA12 drive on the wall would pose a larger arc flash potential than a NEMA1 drive inside of a panel with a PLC.

Or is the arc flash only considered when "working" on the enclosure?
 
One question I have is where is the arc flash potential coming from? Is it the drive itself? There are a lot of drives that are available in NEMA4/12/etc. These are typically placed outside of an enclosure on the wall or unistrut. The NEMA ratings does not change the arc flash potential correct? So you would think that a NEMA12 drive on the wall would pose a larger arc flash potential than a NEMA1 drive inside of a panel with a PLC.

Or is the arc flash only considered when "working" on the enclosure?

https://www.youtube.com/watch?v=4bBvmPRqfmo

A site I was working at had an old school VFD have an arc flash incident, luckily nobody was around it when it happened (just caught it on camera).
 
One question I have is where is the arc flash potential coming from? Is it the drive itself? There are a lot of drives that are available in NEMA4/12/etc. These are typically placed outside of an enclosure on the wall or unistrut. The NEMA ratings does not change the arc flash potential correct? So you would think that a NEMA12 drive on the wall would pose a larger arc flash potential than a NEMA1 drive inside of a panel with a PLC.

Or is the arc flash only considered when "working" on the enclosure?

I'm not an expert, and I don't want to be. The arc flash can occur anytime, but it's effects are most hazardous when the enclosure is open and personnel are in close proximity. I don't know how much a NEMA 1 ventilated enclosure decreases the impact, but I'm sure it helps.

I was standing next to a 300 hp low voltage VFD when it blew. A technician was working on it. No injuries, due to pure good luck, but it sure as he!! scared the bejeezus out of us.
 
So I guess the issue is mitigating exposure to the potential arc flash, not the arc flash itself happening.
I'm obviously not very knowledgeable about this though it is something that I should start to learn.

Tom i'm sure that would have scared the hell out of anyone!
 
One of the most difficult things about arc flash is that it's hard to calculate the potential.


It's not nearly as simple as looking at a chart saying with this voltage and this amperage, then this is your arc flash potential.


I definitely agree with everyone that it's a very important safety issue. I just wish it was easier to calculate and implement.
 

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