"Ignoramus23559" wrote in message
...
On 2012-01-18, Jim Wilkins wrote:

"Cross-Slide" wrote...
-I heard, and saw the aftermath of a 480 Volt arcflash.
-Loudest THUNDERCLAP!! I Ever heard, and I was a building away.
...

I came back after being out sick for a day to find the machine I had been
building black with soot, and on the edge of a perhaps 20 foot black
circle
on the floor. Some new hire engineers had been attempting to find the
correct phasing for a 480V power supply by holding the wires in place by
hand, and apparently one of them slipped- - - - - .

And, what happened to those engineers?

I never saw them again.

Also, how big of a transformer this was on?

100A, it ran the whole factory. I accidentally touched one phase and didn't
get a shock, only a small burn that felt like a sliver.

What I do not fully understand, also, is what role do fuses play in
this. Would a fuse not blow very quickly under such fault conditions?
i

Speculation is that the 480 lead may have touched a large electrolytic
capacitor. I cleaned up my machine and didn't hear any more about the
incident afterwards.

Motor fuses are usually either dual element slow-blow or 3x larger than the
run current.

jsw